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Host specificity encompasses the range and diversity of host species that a parasite is capable of infecting and is considered a crucial measure of a parasite’s potential to shift hosts and trigger disease emergence. Yet empirical studies rarely consider that regional observations only reflect a parasite’s ‘realized’ host range under particular conditions: the true ‘fundamental’ range of host specificity is typically not approached. We provide an overview of challenges and directions in modelling host specificity under variable environmental conditions. Combining tractable modelling frameworks with multiple data sources that account for the strong interplay between a parasite's evolutionary history, transmission mode, and environmental filters that shape host–parasite interactions will improve efforts to quantify emerging disease risk in times of global change.
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... Predicting parasitic disease emergence requires identifying host attributes that enable pathogen spillover and host shifting (Wells et al., 2015;Dallas et al., 2017;Wells and Clark, 2019). Parasite range expansion can generally be explained by ecological fitting (Wells and Clark, 2019). ...
... Predicting parasitic disease emergence requires identifying host attributes that enable pathogen spillover and host shifting (Wells et al., 2015;Dallas et al., 2017;Wells and Clark, 2019). Parasite range expansion can generally be explained by ecological fitting (Wells and Clark, 2019). This theory posits that a shared evolutionary history with a previous host would be necessary for enabling a parasite to circumvent immunological and physiological barriers (Davies and Pedersen, 2008;Hoberg and Brooks, 2008;Wells and Clark, 2019). ...
... Parasite range expansion can generally be explained by ecological fitting (Wells and Clark, 2019). This theory posits that a shared evolutionary history with a previous host would be necessary for enabling a parasite to circumvent immunological and physiological barriers (Davies and Pedersen, 2008;Hoberg and Brooks, 2008;Wells and Clark, 2019). Wells and Clark (2019) suggest that rather than a historical attribute that parasite host shifting is a probabilistic event and relies on opportunity for a parasite to interact with a host under variable environmental conditions. ...
Article
Haemosporidian parasites of the genera Plasmodium, Leucocytozoon, and Haemoproteus are one of the most prevalent and widely studied groups of parasites infecting birds. Plasmodium is the most well-known haemosporidian as the avian parasite Plasmodium relictum was the original transmission model for human malaria and was also responsible for catastrophic effects on native avifauna when introduced to Hawaii. The past two decades has seen a dramatic increase in research on avian haemosporidian parasites as a model system to understand evolutionary and ecological parasite-host relationships. Despite haemosporidians being one the best studied groups of avian parasites their specialization among avian hosts and variation in prevalence amongst regions and host taxa are not fully understood. In this review we focus on describing the current phylogenetic and morphological diversity of haemosporidian parasites, their specificity among avian and vector hosts, and identifying the determinants of haemosporidian prevalence among avian species. We also discuss how these parasites might spread across regions due to global climate change and the importance of avian migratory behavior in parasite dispersion and subsequent diversification.
... The transmission of pathogens between different species, the crossing of species barriers, is an ecological phenomenon known as "host jump", "cross-species transmission", "zoonotic transfer", "pathogen spillover", or "zoonotic spillover" (Lu et al., 2015;Plowright et al., 2017;Knetsch et al., 2018;Becker et al., 2019). Specifically, "spillover" can be defined as the "cross-species transmission of a parasite into a host population not previously infected" (Wells and Clark, 2019). Usually, spillover refers to the cross-species transmission of pathogens from wildlife (vertebrate animals) to humans Wells and Clark, 2019). ...
... Specifically, "spillover" can be defined as the "cross-species transmission of a parasite into a host population not previously infected" (Wells and Clark, 2019). Usually, spillover refers to the cross-species transmission of pathogens from wildlife (vertebrate animals) to humans Wells and Clark, 2019). The transmission of a pathogen from humans to wildlife (reverse zoonosis), by direct contact between species or mediated by vectors, can be called "spillback" (Weaver, 2013;Hendy et al., 2020;Olival et al., 2020). ...
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The transmission of pathogens from wild animals to humans is called “zoonotic spillover”. Most human infectious diseases (60-75%) are derived from pathogens that originally circulated in non-human animal species. This demonstrates that spillover has a fundamental role in the emergence of new human infectious diseases. Understanding the factors that facilitate the transmission of pathogens from wild animals to humans is essential to establish strategies focused on the reduction of the frequency of spillover events. In this context, this article describes the basic aspects of zoonotic spillover and the main factors involved in spillover events, considering the role of the inter-species interactions, phylogenetic distance between host species, environmental drivers, and specific characteristics of the pathogens, animals, and humans. As an example, the factors involved in the emergence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic are discussed, indicating what can be learned from this public health emergency, and what can be applied to the Brazilian scenario. Finally, this article discusses actions to prevent or reduce the frequency of zoonotic spillover events.
... 1. Host specificity is simply defined as the number of recorded host species for a given symbiont species (Lymbery, 1989), but it can also include the phylogenetic relationships among hosts (phylogenetic host specificity) and variation across the geographic ranges (geographic hostspecificity) Wells and Clark, 2019). Host specificity has been widely integrated in coextinction models (Colwell et al., 2012;Moir et al., 2010;Strona, 2015), where highly host-specific symbionts are often expected to have a higher extinction risk, all else being equal. ...
... However, obtaining precise estimates of symbionts' N e is a complicated task (Crellen et al., 2016;Thiele et al., 2018;Criscione, 2013;Strobel et al., 2019). 9. Geographic patchiness: Some symbionts can be found across the whole distribution of their hosts and others are restricted to small areas within the host's distribution (Krasnov et al., 2004;Bush et al., 2009;Poulin, 2011;Clayton et al., 2015;Wells and Clark, 2019;Bush and Kennedy, 1994;Bush et al., 2013). Symbionts restricted to reduced areas of host distribution may have higher extinction risks. ...
Article
Symbionts have a unique mode of life that has attracted the attention of ecologists and evolutionary biologists for centuries. As a result of this attention, these disciplines have produced a mature body of literature on host-symbiont interactions. In contrast, the discipline of symbiont conservation is still in a foundational stage. Here, we aim to integrate methodologies for symbiont coevolutionary biology with symbiont conservation. We focus on host-symbiont cophylogenies, because they have been widely used to study symbiont diversification history and contain information on symbiont extinction. However, cophylogenetic information has never been used nor adapted to the perspective of conservation. Here, we propose a new statistic, “cophylogenetic extinction rate” (Ec), which is based on coevolutionary knowledge from event-based cophylogenetic analyses and could be informative to assess relative symbiont extinction risks. Finally, we propose potential future research to further develop methods to estimate symbiont extinction risk from cophylogenetic analyses, and to continue the integration of this existing knowledge of coevolutionary biology and cophylogenetics into future symbiont conservation studies and practices.
... Greater rates of replication error and higher genetic diversity in RNA virus populations have been proposed to increase their host range through more frequent host shifting and adaptation to distantly related host species, whereas DNA viruses and retroviruses are assumed to be more host specific owing to stronger co-divergence with their hosts over much longer evolutionary time-scales (Cleaveland, Laurenson, & Taylor, 2001;Geoghegan, Duchêne, & Holmes, 2017;Jackson & Charleston, 2004;Longdon et al., 2018). With the mounting recognition that host use in parasites seems to be more constrained by ecological opportunity than by evolutionary history, there is an urgent need to understand and quantify pathogen spread and host-shifting capacity in response to specific traits at a global scale (Nylin et al., 2018;Wells & Clark, 2019). Nevertheless, to date little comprehensive work has explored whether host sharing and virus spread at the network level differ among these types of viruses and whether they interact with the various groups of mammals in different ways. ...
... This might reflect the wide geographical distribution and opportunities for contact with wildlife across biogeographical borders, given that domestic species are not particularly distinguished from wildlife in terms of ecological traits. In fact, opportunity for contact and community assembly have been shown in a number of studies to impact pathogen sharing and host shiftingCooper, Griffin, Franz, Omotayo, & Nunn, 2012;Wells & Clark, 2019). Many pathogens, including viruses, can overcome species F I G U R E 4 Estimated proportion of zoonotic viruses for mammalian host species from different orders (left panel: all n = 1,785 virus species in the database; right panel: estimates for the two main groups of n = 730 DNA virus species and n = 912 RNA virus species). ...
Article
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Emerging infectious diseases arising from pathogen spillover from mammals to humans constitute a substantial health threat. Tracing virus origin and predicting the most likely host species for future spillover events are major objectives in One Health disciplines. We assessed patterns of virus sharing among a large diversity of mammals, including humans and domestic species. We used network centrality analysis and trait‐based Bayesian hierarchical models to explore patterns of virus sharing among mammals. We analysed a global database that compiled the associations between 1,785 virus species and 725 mammalian host species as sourced from automatic screening of meta‐data accompanying published nucleotide sequences between 1950 and 2019. We show that based on current evidence, domesticated mammals hold the most central positions in networks of known mammal–virus associations. Among entire host–virus networks, Carnivora and Chiroptera hold central positions for mainly sharing RNA viruses, whereas ungulates hold central positions for sharing both RNA and DNA viruses with other host species. We revealed strong evidence that DNA viruses were phylogenetically more host specific than RNA viruses. RNA viruses exhibited low functional host specificity despite an overall tendency to infect phylogenetically related species, signifying high potential to shift across hosts with different ecological niches. The frequencies of sharing viruses among hosts and the proportion of zoonotic viruses in hosts were larger for RNA than for DNA viruses. Acknowledging the role of domestic species in addition to host and virus traits in patterns of virus sharing is necessary to improve our understanding of virus spread and spillover in times of global change. Understanding multi‐host virus‐sharing pathways adds focus to curtail disease spread.
... 1. Host specificity: In the most basic sense, host specificity can be defined as the number of 129 recorded hosts for a given symbiont species (Lymbery, 1989). Also, it can include the 130 phylogenetic relationships among hosts (phylogenetic host specificity) and the variation across the 131 geographic range (geographic host-specificity) Wells and Clark, 2019). This 132 variable has been widely integrated in coextinction models ( Colwell et al., 2012;Moir et al., 2010;133 Strona, 2015). ...
... ). Knowledge of these parameters 185 may provide useful insights regarding symbiont Ne.186 9. Geographic patchiness: The geographic ranges of symbionts and hosts do not always match 187 perfectly, with some symbionts almost mirroring the whole distribution of their hosts and others 188 restricted to some small areas of host distribution (Krasnov et al., 2004; Bush et al., 2009; Poulin, 189 2011;Clayton et al., 2015;Wells and Clark, 2019; Bush and Kennedy, 1994; Bush et al., 2013).190Symbionts restricted to reduced areas of host distribution may be expected to have a higher 191 vulnerability of becoming extinct.19210. ...
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Full-text available
Symbionts have a unique mode of life that has attracted the attention of ecologists and evolutionary biologists for centuries. As a result of this attention, these disciplines have produced a mature body of literature on host-symbiont interactions. In contrast, the discipline of symbiont conservation is still in a foundational stage. Here, we aim to integrate methodologies on symbiont coevolutionary biology with the perspective of conservation. We focus on host-symbiont cophylogenies, because they have been widely used to study symbiont diversification history and contain information on symbiont extinction. However, cophylogenetic information has never been used nor adapted to the perspective of conservation. Here, we propose a new statistic, “cophylogenetic extinction rate” (Ec), based on coevolutionary knowledge, that uses data from event-based cophylogenetic analyses, and which could be informative to assess relative symbiont extinction risks. Finally, we propose potential future research to further develop estimation of symbiont extinction risk from cophylogenetic analyses and continue the integration of this existing knowledge of coevolutionary biology and cophylogenetics into future symbiont conservation studies and practices.
... Host shifts of parasites can lead to biological invasions and result in emerging infectious diseases with devastating effects on the populations of the new hosts (Pimentel et al., 2005;Kumschick et al., 2015;Wells and Clark, 2019). A better knowledge of the drivers of host shifts in the natural distribution areas of parasites could help mitigating their negative effects, preventing future invasions (Kolar and Lodge, 2001;Woolhouse et al., 2005) and can contribute to a better understanding of the coevolution between hosts and parasites (Thompson, 1994). ...
... A better knowledge of the drivers of host shifts in the natural distribution areas of parasites could help mitigating their negative effects, preventing future invasions (Kolar and Lodge, 2001;Woolhouse et al., 2005) and can contribute to a better understanding of the coevolution between hosts and parasites (Thompson, 1994). Host shifts can be promoted by high parasite genetic diversity, low host specificity and by introgression between species (Longdon et al., 2014;Depotter et al., 2016;Wells and Clark, 2019), all of which can be studied using molecular tools (Criscione et al., 2005;de Meeus et al., 2007). ...
Article
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Host shifts of parasites are often causing devastating effects in the new hosts. The Varroa genus is known for a lineage of Varroa destructor that shifted to the Western honey bee, Apis mellifera , with disastrous effects on wild populations and the beekeeping industry. Despite this, the biology of Varroa spp. remains poorly understood in its native distribution range, where it naturally parasitizes the Eastern honey bee, Apis cerana . Here, we combined mitochondrial and nuclear DNA analyses with the assessment of mite reproduction to determine the population structure and host specificity of V. destructor and Varroa jacobsonii in Thailand, where both hosts and several Varroa species and haplotypes are sympatric. Our data confirm previously described mite haplogroups, and show three novel haplotypes. Multiple infestations of single host colonies by both mite species and introgression of alleles between V. destructor and V. jacobsonii suggest that hybridization occurs between the two species. Our results indicate that host specificity and population genetic structure in the genus Varroa is more labile than previously thought. The ability of the host shifted V. destructor haplotype to spillback to A. cerana and to hybridize with V. jacobsonii could threaten honey bee populations of Asia and beyond.
... As anthropogenic factors seems to impact the host-parasite relationship(Budria, & Candolin, 2014),Chakraborty et al. (2019) observed parasite diversity to be driven by land use change whilst,Huang et al. (2015) detected parasite diversity to change with host evolutionary distinctiveness and history. Additionally, host specificity becomes a strong determinant of both parasite diversity and prevalence, which provides an opportunity to predict parasite spill-overs and detection of emerging infectious diseases(Wells & Clark, 2019). Basically, parasites with life cycles closely bound to their hosts develop a narrow level of specificity which in turn determines their population structure, abundance and prevalence(Martinů et al 2018). ...
... The parasitic cycle of both genera is not well known, but experimental studies involving Parafilaroides decorus and O. circumlitus have concluded that fish preyed on by pinnipeds, respectively as opaleye (Giretta nigricans) (Dailey, 1970) and turbot (Psetta maxima) (Lehnert et al., 2010), serve an important role as intermediate hosts. The great diversity of parasitic species from the same genus that affect pinnipeds is probably related to the affinity of each parasite to its respective intermediate and definitive hosts; thus, fur seals of the same species and from the same region, which feed on prey from similar habitats, usually have the same parasitic species (Wells and Clark, 2019). ...
Article
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Verminotic pneumonia caused by Parafilaroides spp. nematodes is an underreported disease in beached South American fur seals, with scant literature available on the characteristics of parafilaroidiasis, the nematode itself, as well as its occurrence in pinnipeds in Brazil. The present work aims to identify, describe and detail the histological features of the infection and molecular characteristics of verminotic pneumonia in the South American fur seal. Twenty-six specimens of Arctocephalus australis , found dead on the northern coast of Rio Grande do Sul in 2021, were analysed. These animals were identified and submitted to necropsy and histology. For the molecular identification of metastrongylids, lung fragments were subjected to DNA extraction, polymerase chain reaction targeting the Internal transcribed spacer 2 (ITS-2) gene and subsequent sequencing. In total, 12 animals presented with parasites in the lung parenchyma on histological evaluation, and only 1 showed a granulomatous lung lesion at necropsy. Microscopically, the nematodes were found mainly in the alveoli, associated with little or no inflammatory response, and they had morphological characteristics compatible with metastrongylids. Six ITS-2 gene quality sequences were obtained; after comparative analysis via BLAST, they showed similarity with sequences obtained from Parafilaroides sp. Therefore, verminotic pneumonia caused by Parafilaroides represents an important differential diagnosis of lung disease in South American fur seals found on the northern coast of Rio Grande do Sul.
... Outbreaks of zoonotic infectious disease or reverse zoonotic disease transmission (zooanthroponosis) in humans are caused by the spillover (cross-species spillover) of pathogens from animals, and locations where individuals and animals frequently interact are potential spillover sites [35]. Pathogen potency, host immune defense, and human activities affect spillover events [36]. ...
Article
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Increasing globalization, agricultural intensification, urbanization, and climatic changes have resulted in a significant recent increase in emerging infectious zoonotic diseases. Zoonotic diseases are becoming more common, so innovative, effective, and integrative research is required to better understand their transmission, ecological implications, and dynamics at wildlife-human interfaces. High-throughput sequencing (HTS) methodologies have enormous potential for unraveling these contingencies and improving our understanding, but they are only now beginning to be realized in livestock research. This study investigates the current state of use of sequencing technologies in the detection of livestock pathogens such as bovine, dogs (Canis lupus familiaris), sheep (Ovis aries), pigs (Sus scrofa), horses (Equus caballus), chicken (Gallus gallus domesticus), and ducks (Anatidae) as well as how it can improve the monitoring and detection of zoonotic infections. We also described several high-throughput sequencing approaches for improved detection of known, unknown, and emerging infectious agents, resulting in better infectious disease diagnosis, as well as surveillance of zoonotic infectious diseases. In the coming years, the continued advancement of sequencing technologies will improve livestock research and hasten the development of various new genomic and technological studies on farm animals.
... Host specificity is a crucial factor shaping the distribution and diversity patterns of parasite species. Understanding host specificity is essential in order to characterise the diversity and study the biogeography of parasites (Štefka et al. 2009, Martinů et al. 2018, Bernard et al. 2019, Wells and Clark 2019. Given that the global species richness of parasites is higher than the diversity of non-parasitic species (Windsor 1998) host specificity is of utmost importance for the studies of co-evolution (Blatrix and Herbers 2003), but also coextinction, i.e. the extinction of host species resulting in the extinction of their associated parasite species (Stork and Lyal 1993). ...
Article
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Ligula intestinalis (Linnaeus, 1758) is a tapeworm parasite with a worldwide distribution that uses a wide variety of fish species as its second intermediate host. In the present study, we investigated the prevalence and population genetic structure of plerocercoids of L. intestinalis in five common cyprinoid species, roach Rutilus rutilus (Linnaeus), freshwater bream Abramis brama (Linnaeus), white bream Blicca bjoerkna (Linnaeus), bleak Alburnus alburnus (Linnaeus), and rudd Scardinius erythrophthalmus (Linnaeus), collected in six water bodies of the Czech Republic (Milada, Most, Medard, Jordán, Římov and Lipno). Of the six study sites, the highest frequency of parasitism was recorded in Lake Medard (15%). The overall prevalence rate among the species was as follows: roach > rudd ≥ freshwater bream > bleak > white bream. Two mitochondrial genes (cytb and COI) were used to compare the population genetic structure of parasite populations using selected samples from the five fish species. The results of the phylogenetic analysis indicated that all populations of L. intestinalis were placed in Clade A, previously identified as the most common in Europe. At a finer scale, haplotype network and PCoA analyses indicated the possible emergence of host specificity of several mtDNA haplotypes to the freshwater bream. Moreover, pairwise Fixation indices (FST) revealed a significant genetic structure between the parasite population in freshwater bream and other host species. Parasite populations in roach not only showed the highest rate of prevalence but also depicted a maximum number of shared haplotypes with populations from bleak and rudd. Our results suggest that recent ecological differentiation might have influenced tapeworm populations at a fine evolutionary scale. Thus, the differences in prevalence between fish host species in different lakes might be influenced not only by the parasite's ecology, but also by its genetic diversity.
... In turn, host-parasite interactions are strongly influenced by the parasites' host specificity, which refers to the diversity of host species that a single parasite can infect, and how phylogenetically distant they are from each other. This characteristic can vary geographically as ecological and environmental conditions can modulate the range of host species a parasite can infect (Wells and Clark 2019). Parasites infecting a single or a few closely related species are considered to be more specialized than a parasite lineage capable of infecting a broad range of species, including phylogenetically distant taxa, which would be considered a more generalist parasite (Futuyma and Moreno 1988, Bensch et al. 2000, Moens and Pérez-Tris 2016. ...
Article
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The evolution of host–parasite interactions as host lineages colonize new geographic regions and diversify over evolutionary time is poorly understood. To assess whether haemosporidian parasite diversity has changed during the diversification of an avian host, we surveyed the diversity and prevalence of blood parasite lineages (genera Plasmodium, Haemoproteus, and Leucocytozoon) across the range of the songbird genus Junco, which has diversified recently as it recolonized North America following the last glacial maximum ~18,000 years ago. We report the diversity and prevalence of parasites in junco taxa sampled from Costa Rica to Canada, and examine the influence of local avian species richness in the prevalence and diversity of parasites in junco samples. We screened for parasites in each individual by sequencing a fragment of their cytochrome b gene, identifying the different lineages, and quantifying the prevalence per junco taxon and locality. Of 304 juncos sampled, 178 tested positive for 1 or more parasite genera (58.5% overall prevalence). We found high parasite diversity in genera Haemoproteus and Leucocytozoon and much lower diversity in Plasmodium. Among the 63 parasite lineages detected, 32 of which have not been previously described, we found generalist lineages with widespread but low prevalence in Junco, but also some that appear to have remained specialized on this genus as it diversified across North America over thousands of years. Our results suggest a range of parasitic strategies, ranging from specialized to generalist lineages within single parasite genera.
... However, although often simplified as a static condition, host specificity is often an evolutionarily, geographically, and ecologically dynamic trait (Clark & Clegg, 2017;Poulin et al., 2011;Wells & Clark, 2019). ...
Article
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Host specificity is a fundamental life history trait of symbionts and exists on a broad continuum from symbionts that are specific to one or a few hosts (host specialists), to those associated with multiple different host species (host generalists). However, the biological mechanisms underlying the complexity and wide variation in symbiont host specificity are poorly understood from both the symbiont and host perspectives across many symbiotic systems. Feather mites are common avian symbionts that vary in their host specificity from extreme host generalists to host specialists, even among species within the same genus. Here, we measured and compared survival probability and rate of dispersal to determine how these traits differ between two species of feather mites in the same genus: one host generalist associated with 17 host species (Amerodectes ischyros) and one host specialist with only one known host (A. protonotaria). We initially predicted that the host generalist would live longer and disperse more rapidly but discovered that while the host generalist mite survived longer, the host specialist mite dispersed more quickly. The differing environmental and ecological conditions in which the hosts of these mites are associated may explain the survival and dispersal patterns we uncovered, as differential microclimates may have led to different selective pressures on each species of mite. We also noted mite behavioural observations and suggest experiments to extend our understanding of feather mite ecology and evolution. After removal from their host, host generalist feather mites exhibit significantly longer survival times compared to host specialist mites. Host specialist feather mites have a significantly greater number of expected dispersal events than host generalist mites. Differential selective pressures and ecological contexts may explain the variation in symbiont host specificity.
... Predicting the emergence of infectious diseases at the human-animal interface requires an understanding of how a pathogen may shift from an animal reservoir to humans and emerge causing a zoonotic disease. Generally, host shifting requires a pathogen to be exposed to new hosts that exhibit a level of physiological and/or behavioural overlap with previous hosts through ecological fitting (species association such that an ecological trait profile enables infection by a pathogen without genetic change) (Agosta and Klemens, 2008;Streicker et al., 2010;Wells and Clark, 2019;Woolhouse et al., 2005), or the rapid adaptation of a pathogen to a new host environment in order to break potential barriers caused by variations in host competence or immunity (Parrish et al., 2008). Understanding the associations between reservoir host species, pathogens and humans can only be a critical first step in predicting emergence. ...
Article
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The Covid-19 pandemic is of zoonotic origin, and many other emerging infections of humans have their origin in an animal host population. We review the challenges involved in modelling the dynamics of wildlife-human interfaces governing infectious disease emergence and spread. We argue that we need a better understanding of the dynamic nature of such interfaces, the underpinning diversity of pathogens and host-pathogen association networks, and the scales and frequencies at which environmental conditions enable spillover and host shifting from animals to humans to occur. The major drivers of the emergence of zoonoses are anthropogenic, including the global change in climate and land use. These, and other ecological processes pose challenges that must be overcome to counterbalance pandemic risk. The development of more detailed and nuanced models will provide better tools for analysing and understanding infectious disease emergence and spread.
... Thus, we believe that our approach is valuable to illuminate the changes that occur in host-parasite interactions when an invasive species and its parasite community are introduced into a new area. Further studies could also consider host traits and phylogenetic determinants of parasites, which are known to dictate the success of host-parasite associations (Wells and Clark 2019;Campião and Dáttilo 2020). Furthermore, the analysis of host individual-parasite species interactions as bipartite networks can be useful in other study contexts, such as in prediction and mitigation of impacts of climate change, human activities, and/or habitat loss or fragmentation. ...
Article
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Introduced species can alter the dynamics and structure of a native community. Network analysis provides a tool to study host–parasite interactions that can help to predict the possible impact of biological invasions or other disturbances. In this study, we used weighted bipartite networks to assess differences in the interaction patterns between hosts and helminth parasites of native (Sea of Japan) and invasive (Black Sea and Sea of Azov) populations of Planiliza haematocheilus (Teleostei: Mugilidae). We employed three quantitative network descriptors, connectance, weighted nestedness and modularity, to gain insight into the structure of the host–parasite networks in the native and invaded areas. The role of parasite species in the networks was assessed using the betweenness centrality index. We analyzed networks encompassing the whole helminth community and subsets of species classified by their transmission strategy. The analyses were downscaled to host individual-level to consider intraspecific variation in parasite communities. We found significant differences between networks in the native and invaded areas. The latter presented a higher value of nestedness, which may indicate a co-occurrence between parasite species with many connections in the network and species with fewer interactions within the same individual-host. In addition, modularity was higher in the native area’s networks than those of the invaded area, with subgroups of host individuals that interact more frequently with certain parasite species than with others. Only the networks composed of actively transmitted parasites and ectoparasites did not show significant differences in modularity between the Sea of Azov and the Sea of Japan, which could be due to the introduction of a part of the native community into the invaded environment, with a lower diversity and abundance of species. We show that network analysis provides a valuable tool to illuminate the changes that occur in host–parasite interactions when an invasive species and its parasite community are introduced into a new area.
... Predictions of unobserved host-parasite associations are often based on an assumption that present-day associations accurately reflect potential host ranges [31,35,36]. However, host range is a dynamic property of parasites that evolves through cospeciation, host shifts, and the gains and losses of hosts over varying timescales [37][38][39][40][41]. Changes in parasite host specificity as a result of host-switching and shifting geographic ranges have attracted considerable attention by researchers [42][43][44][45][46][47], whereas extinction history has tended to be overlooked. ...
Article
A growing body of research is focused on the extinction of parasite species in response to host endangerment and declines. Beyond the loss of parasite species richness, host extinction can impact apparent parasite host specificity, as measured by host richness or the phylogenetic distances among hosts. Such impacts on the distribution of parasites across the host phylogeny can have knock-on effects that may reshape the adaptation of both hosts and parasites, ultimately shifting the evolutionary landscape underlying the potential for emergence and the evolution of virulence across hosts. Here, we examine how the reshaping of host phylogenies through extinction may impact the host specificity of parasites, and offer examples from historical extinctions, present-day endangerment, and future projections of biodiversity loss. We suggest that an improved understanding of the impact of host extinction on contemporary host–parasite interactions may shed light on core aspects of disease ecology, including comparative studies of host specificity, virulence evolution in multi-host parasite systems, and future trajectories for host and parasite biodiversity. This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.
... Here, we test this question using avian haemosporidian parasites as a model system. Answering this question is critical because generalist parasites, which are capable of rapidly switching to new host species (Wells & Clark, 2019), are more likely to be associated with emerging infectious diseases (EIDs) (Ewen et al., 2012;Farrell et al., 2013;Hatcher et al., 2012;Johnson et al., 2015a;Timms & Read, 1999), and thus the biotic homogenisation of parasite communities can increase the risk disease emergence. ...
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Niche theory predicts specialists which will be more sensitive to environmental perturbation compared to generalists, a hypothesis receiving broad support in free‐living species. Based on their niche breadth, parasites can also be classified as specialists and generalists, with specialists infecting only a few and generalists a diverse array of host species. Here, using avian haemosporidian parasites infecting wild bird populations inhabiting the Western Ghats, India as a model system, we elucidate how climate, habitat and human disturbance affects parasite prevalence both directly and indirectly via their effects on host diversity. Our data demonstrate that anthropogenic disturbance acts to reduce the prevalence of specialist parasite lineages, while increasing that of generalist lineages. Thus, as in free‐living species, disturbance favours parasite communities dominated by generalist versus specialist species. Because generalist parasites are more likely to cause emerging infectious diseases, such biotic homogenisation of parasite communities could increase disease emergence risk in the Anthropocene. The Anthropocene has been characterised by human‐mediated environmental modifications, such as deforestation and urbanisation. Here, we show that human‐mediated disturbance can favour parasite communities dominated by generalist versus specialist species. Because generalist parasites are more likely to cause emerging infectious diseases, such biotic homogenisation of parasite communities could increase risk of disease emergence in the Anthropocene.
... To address macroecological hypotheses of resource specialization, parasite systems are perhaps some of the most promising (Stephens et al. 2016). For example, the growing availability of host-parasite occurrence data has enabled continent-scale investigations of host specificity (Fecchio et al. 2019, defined as the number or diversity of hosts a parasite can infect (Wells and Clark 2019). In contrast, host specialization (in the Grinnellian sense) refers to variance in species' performance across a range of environments (Futuyma andMoreno 1988, Devictor et al. 2010). ...
Article
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Fitness responses to environment can shape species distributions, though opposing eco‐evolutionary processes can obscure environmental effects. For example, host specificity influences parasite dynamics, but is unclear how adaptation of parasites to local host communities may scale up to continental distributions. Here, we develop a macroecological framework to determine how host community structure affects the distribution of specialist and generalist populations of Striga hermonthica, an African parasitic plant of cereal crops. Combining data from global crop production and parasite experimental trials, we find that parasites perform best on the host species that is most common in their location of origin. Moreover, niche model contrasts predict parasite specialization on two hosts that evolved alongside Striga during domestication (pearl millet and sorghum), indicating that specialist parasites may be most likely to occur where host niches differ most in multivariate environmental space. Our study demonstrates that patterns of parasite local adaptation to host communities can emerge at continental scales and that differential environmental tolerances of hosts indirectly shape the distribution of specialist and generalist parasites. By predicting spatial dynamics of parasite specialization versus generalization directly from environmental data, our approach may help inform current and future management of pests and disease.
... Here, we test this question using avian haemosporidian parasites as a model system. Answering this question is critical because generalist parasites, which are capable of rapidly switching to new host species (Wells & Clark, 2019), are more likely to be associated with emerging infectious diseases (EIDs) (Ewen et al., 2012;Farrell et al., 2013;Hatcher et al., 2012;Johnson et al., 2015a;Timms & Read, 1999), and thus the biotic homogenisation of parasite communities can increase the risk disease emergence. ...
Preprint
Niche theory predicts specialists will be more sensitive to environmental perturbation compared to generalists, a hypothesis receiving broad support in free-living species. Based on their niche breadth, parasites can also be classified as specialists and generalists, with specialists infecting only a few and generalists a diverse array of host species. Here, using avian haemosporidian parasites infecting wild bird populations inhabiting the Western Ghats, India as a model system, we elucidate how climate, habitat and human disturbance affects parasite prevalence both directly and indirectly via their effects on host diversity. Our data demonstrates that anthropogenic disturbance acts to reduce the prevalence of specialist parasite lineages, while increasing that of generalist lineages. Thus, as in free-living species, disturbance favors parasite communities dominated by generalist vs. specialist species. Because generalist parasites are more likely to cause emerging infectious diseases, such biotic homogenization of parasite communities could increase disease emergence risk in the Anthropocene
... The lineages found in thrushes across the Atlantic Forest have been shown to infect a broad range of unrelated host species (Lacorte et al., 2013;Fecchio et al., 2019). Host switching is the main macroevolutionary pattern in haemosporidian diversification (Ricklefs et al., 2004;Fecchio et al., 2018), but rather than a historical attribute, host shifting may rely on opportunities for parasites to infect new hosts under variable environmental conditions (Wells and Clark, 2019). The presence of thrushes harbouring lineages capable of infecting a broad range of avian hosts in disturbed landscapes with low functional diversity may impact avian malaria transmission, leading to increased prevalence and lineage richness among the several host species in the local avian host community. ...
Article
Host phylogenetic relatedness and ecological similarity are thought to contribute to parasite community assembly and infection rates. However, recent landscape level anthropogenic changes may disrupt host-parasite systems by impacting functional and phylogenetic diversity of host communities. We examined whether changes in host functional and phylogenetic diversity, forest cover, and minimum temperature influence the prevalence, diversity, and distributions of avian haemosporidian parasites (genera Haemoproteus and Plasmodium) across 18 avian communities in the Atlantic Forest. To explore spatial patterns in avian haemosporidian prevalence and taxonomic and phylogenetic diversity, we surveyed 2241 individuals belonging to 233 avian species across a deforestation gradient. Mean prevalence and parasite diversity varied considerably across avian communities and parasites responded differently to host attributes and anthropogenic changes. Avian malaria prevalence (termed herein as an infection caused by Plasmodium parasites) was higher in deforested sites, and both Plasmodium prevalence and taxonomic diversity were negatively related to host functional diversity. Increased diversity of avian hosts increased local taxonomic diversity of Plasmodium lineages but decreased phylogenetic diversity of this parasite genus. Temperature and host phylogenetic diversity did not influence prevalence and diversity of haemosporidian parasites. Variation in the diversity of avian host traits that promote parasite encounter and vector exposure (host functional diversity) partially explained the variation in avian malaria prevalence and diversity. Recent anthropogenic landscape transformation (reduced proportion of native forest cover) had a major influence on avian malaria occurrence across the Atlantic Forest. This suggests that, for Plasmodium, host phylogenetic diversity was not a biotic filter to parasite transmission as prevalence was largely explained by host ecological attributes and recent anthropogenic factors. Our results demonstrate that, similar to human malaria and other vector-transmitted pathogens, prevalence of avian malaria parasites will likely increase with deforestation.
... To address macroecological hypotheses of resource specialization, parasite systems are perhaps some of the most promising (Stephens et al. 2016). For example, the growing availability of host-parasite occurrence data has enabled continent-scale investigations of host specificity (Fecchio et al. 2019, defined as the number or diversity of hosts a parasite can infect (Wells and Clark 2019). In contrast, host specialization (in the Grinnellian sense) refers to variance in species' performance across a range of environments (Futuyma andMoreno 1988, Devictor et al. 2010). ...
Preprint
Fitness responses to environment can shape species distributions, though opposing eco-evolutionary processes can obscure environmental effects. For example, host specificity influences parasite dynamics, but is unclear how adaptation of parasites to local host communities may scale up to continental distributions. Here, we develop a macroecological framework to determine how host community structure affects the distribution of specialist and generalist populations of Striga hermonthica, an African parasitic plant of cereal crops. Combining data from global crop production and parasite experimental trials, we find that parasites perform best on the host species that is most common in their location of origin. Moreover, niche model contrasts predict parasite specialization on two hosts that evolved alongside Striga during domestication (pearl millet and sorghum) , indicating that specialist parasites may be most likely to occur where host niches differ most in multivariate environmental space. Our study demonstrates that patterns of parasite local adaptation to host communities can emerge at continental scales and that differential environmental tolerances of hosts indirectly shape the distribution of specialist and generalist parasites. By predicting spatial dynamics of parasite specialization versus generalization directly from environmental data, our approach may help inform current and future management of pests and disease.
... Also, deforestation and encroachment of natural habitats leads to reduced feeding bat habitats forcing them to find alternative sites in peri-urban landscapes and with simultaneous less awareness in building communities' resilience to future outbreaks can increase human exposure to zoonotic disease reservoirs allowing pathogens transfer to other species (United Nations Environment Programme and International Livestock Research Institute 2020). Additionally, climate changes as a force of nature can rapidly influence the geographic distribution and abundance of bats species and increase the incidence of the vector-borne and zoonotic diseases (Wells and Clark 2019). Inter-species transmission of the pathogens is a consequence of the contact between bats and other animals including humans, which potentially could result in disease outbreaks. ...
Article
Full-text available
Bats as flying mammals are potent vectors and natural reservoir hosts for many infectious viruses, bacteria, and fungi, also detected in their excreta such as guano. Accelerated deforestation, urbanization, and anthropization hastily lead to overpopulation of the bats in urban areas allowing easy interaction with other animals, expansion, and emergence of new zoonotic disease outbreaks potentially harmful to humans. Therefore, getting new insights in the microbiome of bat guano from different places represents an imperative for the future. Furthermore, the use of novel high-throughput sequencing technologies allows better insight in guano microbiome and potentially indicated that some species could be typical guano-dwelling members. Bats are well known as a natural reservoir of many zoonotic viruses such as Ebola, Nipah, Marburg, lyssaviruses, rabies, henipaviruses, and many coronaviruses which caused a high number of outbreaks including ongoing COVID-19 pandemic. Additionally, many bacterial and fungal pathogens were identified as common guano residents. Thus, the presence of multi-drug-resistant bacteria as environmental reservoirs of extended spectrum β-lactamases and carbapenemase-producing strains has been confirmed. Bat guano is the most suitable substrate for fungal reproduction and dissemination, including pathogenic yeasts and keratinophilic and dimorphic human pathogenic fungi known as notorious causative agents of severe endemic mycoses like histoplasmosis and fatal cryptococcosis, especially deadly in immunocompromised individuals. This review provides an overview of bat guano microbiota diversity and the significance of autochthonous and pathogenic taxa for humans and the environment, highlighting better understanding in preventing emerging diseases. Key points Bat guano as reservoir and source for spreading of autochthonous and pathogenic microbiota Bat guano vs. novel zoonotic disease outbreaks Destruction of bat natural habitats urgently demands increased human awareness
... To address macroecological hypotheses of resource specialization, parasite systems are perhaps some of the most promising (Stephens et al. 2016). For example, the growing availability of host-parasite occurrence data has enabled continent-scale investigations of host specificity (Fecchio et al. 2019, defined as the number or diversity of hosts a parasite can infect (Wells and Clark 2019). In contrast, host specialization (in the Grinnellian sense) refers to variance in species' performance across a range of environments (Futuyma andMoreno 1988, Devictor et al. 2010). ...
... The capture of a fish paratenic host challenges the phylogenetic conservatism of the genus Profilicollis. However, host specificity cannot be considered a fixed trait, because in spite of being phylogenetically constrained to a large extent, it is strongly influenced by local environmental conditions (Mouillot et al. 2006), which cause considerable variation in realized host specificity (Wells and Clark 2019). Indeed, it has been proposed that estuaries and coastal-brackish lagoons are environments physically variable enough to select generalist genotypes of fish, in order they can adjust their morphology, physiology and behaviour to a wide range of conditions (Bamber and Henderson 1988). ...
Article
Full-text available
Polymorphid acanthocephalans are parasites of marine mammals, waterfowl and ichthyophagous birds. Among these, the genus Profilicollis is known to use exclusively decapods as intermediate hosts. Here, we report the first record of living cystacanths of Profilicollis parasitizing the body cavity of a fish host, Oligosarcus jenynsii, inhabiting the freshwater section of an estuarial system, Mar Chiquita coastal lagoon, in southeast Buenos Aires Province, Argentina. In this environment, cystacanths of Profilicollis chasmagnathi have been previously recorded infecting decapod crabs and as transient accidental infections in the gut of some carcinophagous fishes. In the present study, larvae from the crab Neohelice granulata, from the intestine of the estuarine fish Odontesthes argentinensis and from the body cavity of O. jenynsii were morphologically and genetically compared , confirming their identity as P. chasmagnathi, a species characteristic of estuaries and marine coasts along Argentina, Uruguay and Chile. These findings can be interpreted as a possible case of incipient paratenicity for Profilicollis, and a coloni-zation event of freshwater habitats, probably promoted by the highly variable conditions, typical of ecotonal environments. In addition, cystacanths of the genus Polymorphus were also found in O. jenynsii, representing the first record of this genus in Oligosarcus from Argentina.
... Paratenic or transport hosts are the ones in which parasites do not develop further but remains alive and infective [64]. Parasites exhibit variable degrees of host specificity, with some infecting only a single species or related species (specialists), and some infecting many unrelated species (generalists) [66]. ...
Chapter
Full-text available
Freshwater biodiversity is under constant threat from a range of anthropogenic stressors. Using South Africa’s Phongolo River and floodplain (PRF) as a study case, the aim of this chapter is to provide an overview of the conservation and management of freshwater biodiversity in a highly diverse subtropical ecosystem. The PRF is the largest floodplain system in South Africa which is severely threatened by irregularly controlled flood releases from a large upstream dam, prolonged drought, deteriorating water quality, organic pollutants and the increasing dependence of the local communities. Based on a decade of survey of the PRF conducted from 2010 to 2020, this chapter highlights the current diversity of aquatic organisms (invertebrates, fishes, frogs and their parasitic fauna), followed by an overview of their biological and physical stressors. The current challenges in the management of the aquatic biodiversity of this region and a way forward to conservation strategies are also addressed in this chapter.
... Some parasite species can affect a limited number of host species (also known as highly host-specific). On the contrary, others can be found in many host species, which are considered as generalists [14][15][16]. Parasite-sharing usually depends on the similarity of physiological characteristics among host species, which is likely to be higher in hosts that are closely related phylogenetically and/or share similar feeding habits, ecological niches, or geographic locations [14,[17][18][19][20][21]. According to Rohde [22], a method to estimate parasite host specificity consists of the evaluation of "the number of host species from which the parasite has been collected." ...
Article
Full-text available
Captive birds in zoological settings often harbor parasites, but little information is available about the potential for free-ranging avifauna to act as a source of infection. This review summarizes the gastrointestinal parasitesfound in zoo birds globally and in seven common free-ranging avian species [mallard (Anas platyrhynchos), Eurasian blackbird (Turdus merula), common starling (Sturnus vulgaris), Eurasian jackdaw (Corvus monedula), house sparrow (Passer domesticus), European robin (Erithacus rubecula), and rock dove (Columba livia)] to identify the overlap and discuss the potential for cross species transmission. Over 70 references were assessed, and papers spanned over 90 years from 1925 to 2019. A total of 60 studies from 1987 to 2019 met the eligibility criteria. All examined free-ranging avifauna harbored parasite species that were also reported in zoo birds, except for the European jackdaw. Parasites reported in captive and free-ranging birds include nematodes (Capillaria caudinflata, Dispharynx nasuta, Ornithostrongylus quadriradiatus, Strongyloides avium, Syngamus trachea, and Tetrameres fissispina), cestodes (Dicranotaenia coronula, Diorchis stefanskii, Fimbriaria fasciolaris, and Raillietina cesticillus, Sobolevicanthus gracilis), trematode (Echinostoma revolutum), and protozoa (Cryptosporidium baileyi). Although no study effectively proved cross-transmission either experimentally or by genetic analysis, these parasites demonstrate low host specificity and a high potential for parasite sharing. There is potential for parasite sharing whenever determinants such as host specificity, life cycle, and husbandry are favorable. More research should be carried out to describe parasites in both captive and free-ranging birdsin zoologicalsettings and the likelihood of cross-infection. Such information would contribute to evidence-based control measures, enhancing effective husbandry and preventive medicine protocols.
... Climate change can increase or decrease the incidence of the insect-transmitted Chagas disease, sand-fly transmitted leishmaniasis, and other vector-borne and zoonotic diseases, generally with greater illness occurring at higher degrees of warming. 38 In 2010 in Africa, an outbreak of Rift Valley fever, a mosquito-borne zoonotic disease, occurred with higher than average seasonal rainfall; other outbreaks have occurred even with short periods of heavy rainfall. 16 An extensive literature review of emerging diseases in Brazil revealed relationships between infectious diseases outbreaks and (1) extreme climate events (El Niño, La Niña, heatwaves, droughts, floods, increased temperature, higher rainfall), the frequency of which might be affected by climate change; and (2) environmental changes (habitat fragmentation, deforestation, urbanization, wild meat consumption). ...
Technical Report
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Preventing the Next Pandemic: Zoonotic diseases and how to break the chain of transmission. An evidence-based scientific assessment for policy makers. Unite human, animal and environmental health to prevent the next pandemic – UN Report ● COVID-19 is just one example of the rising trend of diseases – from Ebola to MERS to West Nile and Rift Valley fevers – caused by viruses that have jumped from animal hosts into the human population. ● A new assessment offers ten recommendations, and identifies One Health as the optimal way to prevent and respond to future pandemics. ● The rising trend in zoonotic diseases is driven by the degradation of our natural environment – through land degradation, wildlife exploitation, resource extraction, climate change, and other stresses. Nairobi, 6 July 2020 – As the COVID-19 pandemic continues to take lives and disrupt economies across the world, a new report warns that further outbreaks will emerge unless governments take active measures to prevent other zoonotic diseases from crossing into the human population, and sets out ten recommendations to prevent future pandemics. The report, Preventing the Next Pandemic: Zoonotic diseases and how to break the chain of transmission, is a joint effort by the United Nations Environment Programme (UNEP) and the International Livestock Research Institute (ILRI). It identifies seven trends driving the increasing emergence of zoonotic diseases, including increased demand for animal protein; a rise in intense and unsustainable farming; the increased use and exploitation of wildlife; and the climate crisis. The report finds that Africa in particular, which has experienced and responded to a number of zoonotic epidemics including most recently, to Ebola outbreaks, could be a source of important solutions to quell future outbreaks. 10 recommendations The report identifies ten practical steps that governments can take to prevent future zoonotic outbreaks: ● Investing in interdisciplinary approaches, including One Health; ● Expanding scientific enquiry into zoonotic diseases; ● Improving cost-benefit analyses of interventions to include full-cost accounting of societal impacts of disease; ● Raising awareness of zoonotic diseases; ● Strengthening monitoring and regulation practices associated with zoonotic diseases, including food systems; ● Incentivizing sustainable land management practices and developing alternatives for food security and livelihoods that do not rely on the destruction of habitats and biodiversity; ● Improving biosecurity and control, identifying key drivers of emerging diseases in animal husbandry and encouraging proven management and zoonotic disease control measures; ● Supporting the sustainable management of landscapes and seascapes that enhance sustainable co-existence of agriculture and wildlife; ● Strengthening capacities among health stakeholders in all countries; and ● Operationalizing the One Health approach in land-use and sustainable development planning, implementation and monitoring, among other fields.
... Our results clearly indicate that Sarcocystis scandentiborneensis belongs to a different genetic lineage than S. tupaia with regard to its 18S rDNA sequence, expanding the S1 subclade of Sarcocystis spp. with snake-rodent life cycle (Wassermann et al., 2017) to include a new host order, the Scandentia. The observation that S. scandentiborneensis infects treeshrews showcases that taxon sampling in this group of Sarcocystis spp. was insufficient until today to infer pattern of host sharing and shifting (Wells and Clark, 2019), so that finding a Sarcocystis sp. of this genetic lineage that utilizes a non-rodent intermediate host was overdue. Because host sampling has been largely focussed on murid rodents, particularly in Southeast Asia (Kan and Pathmanathan, 1991;Jäkel et al., 1997;Paperna et al., 2004;Fong et al., 2014), future examination of other Rodentia (e.g., squirrels) or non-rodent taxa (e.g., Lagomorpha, Eulipothyphla) likely to be predated by suitable definite hosts to close transmission cycles could reveal interesting insights into the host spectrum of already known and new Sarcocystis spp. in the wild. ...
Article
Full-text available
Sarcocystis scandentiborneensis sp. nov. was discovered in histological sections of striated musculature of treeshrews (Tupaia minor, T. tana) from Northern Borneo. Sarcocysts were cigar-shaped, 102 μm–545 μm long, and on average 53 μm in diameter. The striated cyst wall varied in thickness (2–10 μm), depending on whether the finger-like, villous protrusions (VP) were bent. Ultrastructurally, sarcocysts were similar to wall type 12 but basal microtubules extended into VPs that tapered off with a unique U-shaped, electron-dense apical structure. In phylogenetic trees of the nuclear 18S rRNA gene, S. scandentiborneensis formed a distinct branch within a monophyletic subclade of Sarcocystis spp. with (colubrid) snake-rodent life cycle. We mapped all intraspecific (two haplotypes) and interspecific nucleotide substitutions to the secondary structure of the 18S rRNA gene: in both cases, the highest variability occurred within helices V2 and V4 but intraspecific variability mostly related to transitions, while transition/transversion ratios between S. scandentiborneensis, S. zuoi, and S. clethrionomyelaphis were skewed towards transversions. Lack of relevant sequences restricted phylogenetic analysis of the mitochondrial Cytochrome C oxidase subunit I (COI) gene to include only one species of Sarcocystis recovered from a snake host (S. pantherophisi) with which the new species formed a sister relationship. We confirm the presence of the functionally important elements of the COI barcode amino acid sequence of S. scandentiborneensis, whereby the frequency of functionally important amino acids (Alanine, Serine) was markedly different to other taxa of the Sarcocystidae. We regard S. scandentiborneensis a new species, highlighting that structurally or functionally important aspects of the 18S rRNA and COI could expand their utility for delineation of species. We also address the question why treeshrews, believed to be close to primates, carry a parasite that is genetically close to a Sarcocystis lineage preferably developing in the Rodentia as intermediate hosts.
... Climate change can increase or decrease the incidence of the insect-transmitted Chagas disease, sand-fly transmitted leishmaniasis, and other vector-borne and zoonotic diseases, generally with greater illness occurring at higher degrees of warming. 38 In 2010 in Africa, an outbreak of Rift Valley fever, a mosquito-borne zoonotic disease, occurred with higher than average seasonal rainfall; other outbreaks have occurred even with short periods of heavy rainfall. 16 An extensive literature review of emerging diseases in Brazil revealed relationships between infectious diseases outbreaks and (1) extreme climate events (El Niño, La Niña, heatwaves, droughts, floods, increased temperature, higher rainfall), the frequency of which might be affected by climate change; and (2) environmental changes (habitat fragmentation, deforestation, urbanization, wild meat consumption). ...
Technical Report
Full-text available
The emergence of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) at the end of 2019 and the vast global public health and economic impacts this novel coronavirus is causing in 2020 are treated as a crisis. While pandemics such as this are sometimes seen as a “black swan”—an extremely rare event—they are actually a widely predicted consequence of how people source food, trade animals, and alter environments.
... In other words, host-specific (and likely rare) and host-opportunistic (and likely widespread) flea species may have different levels of environmental tolerance and, as suggested by our results, may even be sensitive to different environmental factors. No information supporting differential sensitivity to environment in host-specific versus host-opportunistic parasites is available, especially given that the degree of parasite host specificity may vary geographically and in response to environmental conditions (Fecchio et al., 2019;Wells and Clark, 2019; but see Krasnov et al., 2004). Nevertheless, studies of the relationships between environmental tolerance and the level of commonness in free-living organisms (e.g., Boulangeat et al., 2012;Dangremond et al., 2015) suggest that this can also be the case for parasites. ...
Article
We investigated drivers of species turnover in fleas parasitic on small mammals in four biogeographic realms using novel methodology (zeta diversity, and Multi-Site Generalised Dissimilarity Modelling (MS-GDM)). We asked whether (i) flea turnover was better explained by host turnover or environmental variables; (ii) different factors drive the turnover of rare and widespread fleas; (iii) the factors affecting the turnover of rare or widespread fleas differ between realms; and (iv) environmental variables drive flea turnover directly or via their effects on hosts. Dissimilarity in host species composition was the most important factor affecting flea turnover in all realms. In the Afrotropics, the Nearctic, and the Neotropics, this was true mainly for rare species, whereas the zeta diversity of the Palearctic hosts exerted a strong effect on the turnover of both rare and widespread fleas. Dissimilarity in temperature contributed the most to the turnover of rare fleas in the Neotropics and the Palearctic, whereas the turnover of widespread species in these realms was strongly affected by dissimilarity in precipitation. In the Nearctic, dissimilarity in precipitation or temperature mostly affected the turnover of rare fleas or common species, respectively. In the Afrotropics, dissimilarity in the Normalized Difference Vegetation Index (NDVI) and temperature affected the turnover of all species, independently of their level of commonness, while dissimilarity in rainfall was important for the turnover of rare fleas. The responses of flea assemblages to environmental factors represented a combination of direct responses and responses mediated via effects on host turnover. We conclude that host turnover is a more important factor than environmental dissimilarity in its effect on flea species turnover. However, the relative effects of host composition and environment, as well as those of temperature, precipitation and the amount of vegetation, on flea turnover differ (i) between realms and (ii) between rare and common fleas.
... Phylogenetic analysis of molecular data is fundamental as it allows insights into evolutionary history of all forms of life, including parasites and lay the foundation for recognizing and diagnosing species (De Meeus and Renaud, 2002). Moreover, in the case of parasitic relationships, phylogenies of both hosts and parasites, associated with a good knowledge of host ecological relationships, may help to formulate predictions of future outbreaks by identifying evolutionary lineages with significant hostswitching potential (Alcala et al., 2017;Guth et al., 2019;Wells and Clark, 2019). Complete phylogenies of parasites can provide hypotheses on their origin, their diversification as well as changes of their life cycle (Suzán et al., 2015). ...
Article
Understanding geographic patterns of interaction between hosts and parasites can provide useful insight into the evolutionary history of the organisms involved. However, poor taxon sampling often hinders meaningful phylogenetic descriptions of groups of parasites. Trypanosome parasites that constitute the Trypanosoma cruzi clade are worldwide distributed infecting several mammalian species, especially bats. Diversity in this clade has been recently expanded by newly discovered species, but the common ancestor and geographical origins of this group of blood parasites are still debated. We present here results based on the molecular characterization of trypanosome isolates obtained from 1,493 bats representing 74 species and sampled over 16 countries across four continents. After estimating the appropriate number of hypothetical species in our data set using GMYC models in combination with Poisson Tree Processes (mPTP) and ABGD, the 18S rRNA and gGAPDH genes were used for phylogenetic analyses to infer the major evolutionary relationships in the T. cruzi clade. Then, biogeographical processes influencing the distribution of this cosmopolitan group of parasites was inferred using BioGeoBEARS. Results revealed a large lineages diversity and the presence of trypanosomes in all sampled regions which infected 344 individuals from 31 bat species. We found eight Trypanosoma species, including: five previously known; one subspecies of Trypanosoma livingstonei (Trypanosoma cf. livingstonei); and two undescribed taxa (Trypanosoma sp. 1, Trypanosoma sp. 2), which were found exclusively in bats of the genus Miniopterus from Europe and Africa. The new taxa discovered have both an unexpected position in the global phylogeny of the T. cruzi clade. Trypanosoma sp. 1 is a sister lineage of T. livingstonei which is located at the base of the tree, whereas Trypanosoma sp. 2 is a sister lineage of the Shizotrypanum subclade that contains T. c. cruzi and T. dionisii. Ancestral areas reconstruction provided evidence that trypanosomes of the T. cruzi clade have radiated from Africa through several dispersion events across the world. We discuss the impact of these findings on the biogeography and taxonomy of this important clade of parasites and question the role played by bats, especially those from the genus Miniopterus, on the dispersal of these protozoan parasites between continents.
... R. Soc. B 286: 20191811 increase diversity and reduce inbreeding [43], a risk may be that new individuals, new species and changes in ecological opportunities bring in new parasites to the population [44,45]. There is potential here for an increased overlap between host populations with low genetic diversity and novel infections. ...
Article
There is evidence that human activities are reducing the population genetic diversity of species worldwide. Given the prediction that parasites better exploit genetically homogeneous host populations, many species could be vulnerable to disease outbreaks. While agricultural studies have shown the devastating effects of infectious disease in crop monocultures, the widespread nature of this diversity-disease relationship remains unclear in natural systems. Here, we provide broad support that high population genetic diversity can protect against infectious disease by conducting a meta-analysis of 23 studies, with a total of 67 effect sizes. We found that parasite functional group (micro- or macroparasite) affects the presence of the effect and study setting (field or laboratory-based environment) influences the magnitude. Our study also suggests that host genetic diversity is overall a robust defence against infection regardless of host reproduction, parasite host range, parasite diversity, virulence and the method by which parasite success was recorded. Combined, these results highlight the importance of monitoring declines of host population genetic diversity as shifts in parasite distributions could have devastating effects on at-risk populations in nature.
... It has therefore been argued that invasive parasites show higher virulence in endemic species that lack the resistance the original host has gained via co-evolution (naive host syndrome (Mastitsky et al., 2010)). Consequently, differences in susceptibility to parasitic infections in sympatric host species may derive from differences in host-parasite co-evolution (Wells and Clark, 2019). ...
Article
Full-text available
The dynamic relationship of vector-borne parasites, arthropod vectors and their hosts is prone to change under the influence of climate change, global integration, shifting demographics and deforestation. It is therefore essential to better understand parasitism in wildlife populations, including parasites transmitted by blood-feeding vectors, and explore host range and heterogeneity of parasitic infections. We investigated Giemsa stained blood smears of two sympatric Malagasy primate species (Microcebus murinus: 184 samples from 69 individuals and M. ravelobensis: 264 samples from 91 individuals) for blood-stage parasites and tested for a potential influence of host species, sex, body mass and sampling month on blood-stage parasite prevalence and infection intensity. No protozoan parasites were detected in either host species. A host-specific difference was observed in filarial nematode infections, with higher risk of infection in M. murinus (prevalence 30.43%), than in M. ravelobensis (prevalence 6.59%), which may be explained by differences in host behavior and/or immune competence, linked to the period of host-parasite coevolution. Neither sex nor sampling month influenced infection prevalence or intensity significantly. We did not observe a negative effect of microfilarial infections on host fitness when taking body mass as a proxy. Our results support the hypothesis of a long-term evolutionary adaptation of hosts and parasites, leading to persistent infection with low morbidity. Morphological and molecular analyses indicate the finding of a new species, "Lemurfilaria lemuris". Genetic analysis furthermore showed >99% sequence identity with microfilariae described from a sympatric, larger-bodied lemur species of a different genus, suggesting low host-specificity of the detected filariae and pathogen transmission across genus boundaries. Findings contribute to a more comprehensive picture of vector-borne diseases of Malagasy lemurs.
Article
Disentangling the influence of hosts and environmental factors in parasite community assembly is one of the main challenges in disease ecology. Here we used three approaches to assess the influence of host ecology and evolutionary history, as well as environmental factors on Plasmodium parasite composition within the Atlantic Forest. Using sampling data of 2241 bird individuals captured within the Brazilian Atlantic Forest, we first calculated the functional and phylogenetic host specificity of Plasmodium lineages. We then tested whether host functional or phylogenetic distance predicts Plasmodium taxonomic and phylogenetic beta diversity among host species. Finally, we tested if temperature, precipitation, landscape dissimilarity, and host turnover (taxonomic, functional, and phylogenetic) determine Plasmodium taxonomic and phylogenetic turnover among 13 localities within the Atlantic Forest. We found that 47% of the parasite lineages were more phylogenetic specialists than expected by chance. In addition, both taxonomic and phylogenetic Plasmodium beta diversity were associated with host phylogenetic distance, indicating that closely related avian species are infected by assemblages composed of more closely related Plasmodium lineages. When comparing Plasmodium lineage community among localities, we found host phylogenetic turnover as the most relevant predictor of Plasmodium taxonomic and phylogenetic turnover. On the other hand, environmental variables explained 23% of Plasmodium taxonomic turnover among localities, suggesting that lineage composition is affected by climate and landscape, especially temperature seasonality. Combining all results, our findings suggest host phylogeny is the main driver of the regional Plasmodium assemblages within the Atlantic Forest.
Article
Histoplasmosis is a mycotic infection principally affecting pulmonary tissue; sometimes, histoplasmosis can progress into a systemic disease. This infection involves immunocompetent and immunosuppressed human and other mammalian hosts, depending on particular circumstances. Histoplasmosis infection has been documented worldwide. The infection is acquired by inhaling infective mycelial propagules of the dimorphic fungus Histoplasma capsulatum. New reports of clinical cases of histoplasmosis in extreme latitudes could be related to human social adaptations and climate changes in the world, which are creating new favorable environments for this fungus and for bats, its major natural reservoirs and dispersers. Histoplasma has been isolated from most continents, and it is considered a complex of cryptic species, consisting of various groups of isolates that differ genetically and correlate with a particular geographic distribution. Based on updated studies, Histoplasma taxonomy is adjusting to new genetic data. Here, we have suggested that Histoplasma has at least 14 phylogenetic species distributed worldwide and new genotypes that could be under deliberation. Histoplasma's geographic radiation began in South America millions of years ago when the continents were joined and the climate was favorable. For fungal spreading, the role of bats and some birds is crucial, although other natural factors could also participate.
Article
Interactor richness in host–parasite networks, corresponding to either parasite species richness for host species or host range for parasite species, can be a function of taxonomic or trait constraints. Species appearing in multiple networks can have similar interactor richness in each network owing to these taxonomic and trait constraints, resulting in a spatially conserved mean interactor richness and lower variation in interaction richness relative to a null expectation. Here, we used a global database of host–helminth interactions to examine the variability in interactor richness across a spatially explicit collection of 299 host–helminth networks. Global. 1800–2003. Helminth parasite species and their host species. We used randomization tests to examine spatial conservation of species interactions for both host and helminth species. We failed to detect a signal of interactor richness conservation for > 95% of host and helminth parasite species relative to a set of three null models, where both the mean number of interactions per species and the variation in the number of interactions per species did not differ from a random draw. Furthermore, we detected a significant taxonomic signal in divergence in parasite species richness from a null model for host species, indicating that slight departures from null expectations are related to host phylogenetic relationships. Overall, this indicates that interactor richness can vary widely for the same species and that host and helminth parasite species can play very different functional roles in interaction networks across spatial or environmental gradients.
Article
Plant–pathogens and insect pests, hereafter pests, play an important role in structuring ecological communities, yet both native and introduced pests impose significant pressure on wild and managed systems, and pose a threat to food security. Global changes in climate and land use, and transportation of plants and pests around the globe are likely to further increase the range, frequency and severity of pest outbreaks in the future. Thus, there is a critical need to expand on current ecological theory to address these challenges. Here, we outline a phylogenetic framework for the study of plant and pest interactions. In plants, a growing body of work has suggested that evolutionary relatedness, phylogeny, strongly structures plant-pest associations—from pest host breadths and impacts, to their establishment and spread in new regions. Understanding the phylogenetic dimensions of plant-pest associations will help to inform models of invasive species spread, disease and pest risk in crops, and emerging pest outbreaks in native plant communities—which will have important implications for protecting food security and biodiversity into the future. This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.
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Parasite range expansions are a direct consequence of globalization and are an increasing threat to biodiversity. Here, we report a recent range expansion of the SGS1 strain of a highly invasive parasite, Plasmodium relictum , to two non-migratory passerines in North America . Plasmodium relictum is considered one of the world's most invasive parasites and causes the disease avian malaria: this is the first reported case of SGS1 in wild non-migratory birds on the continent. Using a long-term database where researchers report avian malaria parasite infections, we summarized our current understanding of the geographical range of SGS1 and its known hosts. We also identified the most likely geographical region of this introduction event using the MSP1 allele. We hypothesize that this introduction resulted from movements of captive birds and subsequent spillover to native bird populations, via the presence of competent vectors and ecological fitting. Further work should be conducted to determine the extent to which SGS1 has spread following its introduction in North America.
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The persistence of a parasite species in an ecological community is determined both by its environmental tolerance and host breadth. The relative contribution of these niche characteristics to parasite community structure is challenging to parse because host persistence is also a consequence of extrinsic environmental factors. We investigated haemosporidian parasites (genera Plasmodium, Leucocytozoon, and Haemoproteus) in a clade of avian hosts in eastern North America. Species in this clade of Catharus thrushes occupy specific elevational bands in a non‐phylogenetically determined manner. This allowed us to tease apart the effects of host relatedness and elevation on parasite community structure, diversity, and infection prevalence. We screened blood and tissue samples from 414 adult birds from four mountain ranges in the Appalachian Highlands for blood parasites using a cytochrome‐b‐nested PCR protocol and identified parasite lineages by sequencing. We found an overall infection prevalence of 88.4% and identified a total of 38 parasite lineages including six novel lineages. Parasite community patterns varied by genus. Host relatedness rather than elevational zone predicted the beta turnover and phylobeta turnover of Leucocytozoon parasites, indicating that closely related rather than geographically proximate host species had more similar parasites. This pattern was not seen in Plasmodium parasites because the diversity of this parasite genus varied considerably in the high elevational zones among mountain ranges, that is, a sky‐island effect. Haemoproteus parasites were rare in this study system. Our study suggests that the mechanisms that underlie community structuring vary between haemosporidian genera due to differences in the degree of host sharing among lineages.
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Understanding the processes responsible for structuring communities has been a challenge in ecology, and parasite communities are an excellent system to address this issue. The use of different diversity metrics can help us to understand the determinants of the structure of parasite communities, and in this sense, functional diversity indexes make it possible to measure the variability of organism traits in communities. In this study, we investigate how host body size and habitat use influence the functional diversity of nematode parasite infracommunities. We collected and examined 213 individuals of 11 species of anurans in an area of the Brazilian Atlantic Forest, calculated Rao’s quadratic entropy as a measure of functional diversity of parasite infracommunities, and tested if this index was related to host body size and habitat use with an analysis of covariance (ANCOVA). Anuran species varied in body size (from 1.80 to 10.35 cm) and habit use (arboreal, terrestrial, and semiaquatic), and in the functional diversity of parasite infracommunities (Rao’s quadratic entropy ranged from 0 to 0.196). We observed that anurans with larger body size and terrestrial habit showed significantly greater functional diversity of parasites. We conclude that anuran characteristics drive the functional diversity of nematode parasite communities, and highlight the importance of using different diversity metrics to understand the determinants in the host-parasite interaction.
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An extraordinary surge in the number and quality of avian haemosporidian studies in the Neotropics is unveiling the complex ecology and evolution of a successful group of parasites that have a global distribution and staggering diversity. However, despite avian haemosporidian parasites being ubiquitous, many factors still limit our understanding of their diversity. First, traditional taxonomy demands information that is relatively challenging to scale up, so several molecular lineages that are likely new species remain as "dark taxa". Second, there exists only a limited characterization of how parasites inhabit multiple hosts from a handful of censuses. Third, an understanding of the temporal and spatial scales of speciation in this group is limited by a framework built on associations and general patterns. These factors will be discussed by explaining how species are described and delimited, how the available evidence provides insight into possible mechanisms that may elucidate the staggering diversity of haemosporidian parasites, and finally, how the available tools allow us to make preliminary inferences about the time scale of such speciation processes. Although broad in scope, this chapter highlights the need for understanding community-level processes to explain the origins and speciation in this parasite group.
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Parasites with low host specificity (e.g. infecting a large diversity of host species) are of special interest in disease ecology, as they are likely more capable of circumventing ecological or evolutionary barriers to infect new hosts than are specialist parasites. Yet for many parasites, host specificity is not fixed and can vary in response to environmental conditions. Using data on host associations for avian malaria parasites (Apicomplexa: Haemosporida), we develop a hierarchical model that quantifies this environmental dependency by partitioning host specificity variation into region‐ and parasite‐level effects. Parasites were generally phylogenetic host specialists, infecting phylogenetically clustered subsets of available avian hosts. However, the magnitude of this specialisation varied biogeographically, with parasites exhibiting higher host specificity in regions with more pronounced rainfall seasonality and wetter dry seasons. Recognising the environmental dependency of parasite specialisation can provide useful leverage for improving predictions of infection risk in response to global climate change.
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Methods for modeling species’ distributions in nature are typically evaluated empirically with respect to data from observations of species occurrence and, occasionally, absence at surveyed locations. Such models are relatively “theory‐free.” In contrast, theories for explaining species’ distributions draw on concepts like fitness, niche, and environmental suitability. This paper proposes that environmental suitability be defined as the conditional probability of occurrence of a species given the state of the environment at a location. Any quantity that is proportional to this probability is a measure of relative suitability and the support of this probability is the niche. This formulation suggests new methods for presence‐background modeling of species distributions that unify statistical methodology with the conceptual framework of niche theory. One method, the plug‐and‐play approach, is introduced for the first time. Variations on the plug‐and‐play approach were studied with respect to their numerical performance on 106 species from an exhaustively sampled presence–absence survey of vegetation in the Canton of Vaud, Switzerland. Additionally, we looked at the robustness of these methods to the presence of irrelevant information and sample size. Although irrelevant variables eroded the predictive performance of all methods, these methods were found to be both numerically and statistically robust.
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Identifying barriers that govern parasite community assembly and parasite invasion risk is critical to understand how shifting host ranges impact disease emergence. We studied regional variation in the phylogenetic compositions of bird species and their blood parasites (Plasmodium and Haemoproteus spp.) to identify barriers that shape parasite community assembly. Australasia and Oceania. We used a data set of parasite infections from >10,000 host individuals sampled across 29 bioregions. Hierarchical models and matrix regressions were used to assess the relative influences of interspecies (host community connectivity and local phylogenetic distinctiveness), climate and geographic barriers on parasite local distinctiveness and composition. Parasites were more locally distinct (co-occurred with distantly related parasites) when infecting locally distinct hosts, but less distinct (co-occurred with closely related parasites) in areas with increased host diversity and community connectivity (a proxy for parasite dispersal potential). Turnover and the phylogenetic symmetry of parasite communities were jointly driven by host turnover, climate similarity and geographic distance. Interspecies barriers linked to host phylogeny and dispersal shape parasite assembly, perhaps by limiting parasite establishment or local diversification. Infecting hosts that co-occur with few related species decreases a parasite's likelihood of encountering related competitors, perhaps increasing invasion potential but decreasing diversification opportunity. While climate partially constrains parasite distributions, future host range expansions that spread distinct parasites and diminish barriers to host shifting will likely be key drivers of parasite invasions.
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Community ecology aims to understand what factors determine the assembly and dynamics of species assemblages at different spatiotemporal scales. To facilitate the integration between conceptual and statistical approaches in community ecology, we propose Hierarchical Modelling of Species Communities (HMSC) as a general, flexible framework for modern analysis of community data. While non-manipulative data allow for only correlative and not causal inference, this framework facilitates the formulation of data-driven hypotheses regarding the processes that structure communities. We model environmental filtering by variation and covariation in the responses of individual species to the characteristics of their environment, with potential contingencies on species traits and phylogenetic relationships. We capture biotic assembly rules by species-to-species association matrices, which may be estimated at multiple spatial or temporal scales. We operationalise the HMSC framework as a hierarchical Bayesian joint species distribution model, and implement it as R- and Matlab-packages which enable computationally efficient analyses of large data sets. Armed with this tool, community ecologists can make sense of many types of data, including spatially explicit data and time-series data. We illustrate the use of this framework through a series of diverse ecological examples.
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Experimental work increasingly suggests that non-random pathogen associations can affect the spread or severity of disease. Yet due to difficulties distinguishing and interpreting co-infections, evidence for the presence and directionality of pathogen co-occurrences in wildlife is rudimentary. We provide empirical evidence for pathogen co-occurrences by analysing infection matrices for avian malaria (Haemoproteus and Plasmodium spp.) and parasitic filarial nematodes (microfilariae) in wild birds (New Caledonian Zosterops spp.). Using visual and genus-specific molecular parasite screening, we identified high levels of co-infections that would have been missed using PCR alone. Avian malaria lineages were assigned to species level using morphological descriptions. We estimated parasite co-occurrence probabilities, while accounting for environmental predictors, in a hierarchical multivariate logistic regression. Co-infections occurred in 36% of infected birds. We identified both positively and negatively correlated parasite co-occurrence probabilities when accounting for host, habitat and island effects. Two of three pairwise avian malaria co-occurrences were strongly negative, despite each malaria parasite occurring across all islands and habitats. Birds with microfilariae had elevated heterophil to lymphocyte ratios and were all co-infected with avian malaria, consistent with evidence that host immune modulation by parasitic nematodes facilitates malaria co-infections. Importantly, co-occurrence patterns with microfilariae varied in direction among avian malaria species; two malaria parasites correlated positively but a third correlated negatively with microfilariae. We show that wildlife co-infections are frequent, possibly affecting infection rates through competition or facilitation. We argue that combining multiple diagnostic screening methods with multivariate logistic regression offers a platform to disentangle impacts of environmental factors and parasite co-occurrences on wildlife disease. Experimental work increasingly suggests that non-random pathogen associations can affect the spread or severity of disease. Yet due to difficulties distinguishing and interpreting co-infections, evidence for the presence and directionality of pathogen co-occurrences in wildlife is rudimentary. We provide empirical evidence for pathogen co-occurrences by analysing infection matrices for avian malaria (Haemoproteus and Plasmodium spp.) and parasitic filarial nematodes (microfilariae) in wild birds (New Caledonian Zosterops spp.). Using visual and genus-specific molecular parasite screening, we identified high levels of co-infections that would have been missed using PCR alone. Avian malaria lineages were assigned to species level using morphological descriptions. We estimated parasite co-occurrence probabilities, while accounting for environmental predictors, in a hierarchical multivariate logistic regression. Co-infections occurred in 36% of infected birds. We identified both positively and negatively correlated parasite co-occurrence probabilities when accounting for host, habitat and island effects. Two of three pairwise avian malaria co-occurrences were strongly negative, despite each malaria parasite occurring across all islands and habitats. Birds with microfilariae had elevated heterophil to lymphocyte ratios and were all co-infected with avian malaria, consistent with evidence that host immune modulation by parasitic nematodes facilitates malaria co-infections. Importantly, co-occurrence patterns with microfilariae varied in direction among avian malaria species; two malaria parasites correlated positively but a third correlated negatively with microfilariae. We show that wildlife co-infections are frequent, possibly affecting infection rates through competition or facilitation. We argue that combining multiple diagnostic screening methods with multivariate logistic regression offers a platform to disentangle impacts of environmental factors and parasite co-occurrences on wildlife disease.
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Estimating population spread rates across multiple species is vital for projecting biodiversity responses to climate change. A major challenge is to parameterise spread models for many species. We introduce an approach that addresses this challenge, coupling a trait-based analysis with spatial population modelling to project spread rates for 15 000 virtual mammals with life histories that reflect those seen in the real world. Covariances among life history traits are estimated from an extensive terrestrial mammal data set using Bayesian inference. We elucidate the relative roles of different life-history traits in driving modelled spread rates, demonstrating that any one alone will be a poor predictor. We also estimate that around 30% of mammal species have potential spread rates slower than the global mean velocity of climate change. This novel trait-space-demographic modelling approach has broad applicability for tackling many key ecological questions for which we have the models but are hindered by data availability.
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Despite the fact that parasites are highly specialized with respect to their hosts, empirical evidence demonstrates that host switching rather than co-speciation is the dominant factor influencing the diversification of host-parasite associations. Ecological fitting in sloppy fitness space has been proposed as a mechanism allowing ecological specialists to host-switch readily. That proposal is tested herein using an individual-based model of host switching. The model considers a parasite species exposed to multiple host resources. Through time host range expansion can occur readily without the prior evolution of novel genetic capacities. It also produces non-linear variation in the size of the fitness space. The capacity for host colonization is strongly influenced by propagule pressure early in the process and by the size of the fitness space later. The simulations suggest that co-adaptation may be initiated by the temporary loss of less fit phenotypes. Further, parasites can persist for extended periods in sub-optimal hosts, and thus may colonize distantly related hosts by a "stepping-stone" process.
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