Increased Host Species Diversity and Decreased Prevalence of Sin Nombre Virus

Portland State University, Portland, Oregon 97207-0751, USA.
Emerging Infectious Diseases (Impact Factor: 7.33). 08/2009; 15(7):1012-8. DOI: 10.3201/eid1507.081083
Source: PubMed

ABSTRACT Emerging outbreaks of zoonotic diseases are affecting humans at an alarming rate. Until the ecological factors associated with zoonoses are better understood, disease emergence will continue. For Lyme disease, disease suppression has been demonstrated by a dilution effect, whereby increasing species diversity decreases disease prevalence in host populations. To test the dilution effect in another disease, we examined 17 ecological variables associated with prevalence of the directly transmitted Sin Nombre virus (genus Hantavirus, etiologic agent of hantavirus pulmonary syndrome) in its wildlife host, the deer mouse (Peromyscus maniculatus). Only species diversity was statistically linked to infection prevalence: as species diversity decreased, infection prevalence increased. The increase was moderate, but prevalence increased exponentially at low levels of diversity, a phenomenon described as zoonotic release. The results suggest that species diversity affects disease emergence.

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Available from: Luis A. Ruedas, Jan 10, 2014
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    • "A concurrent extension of this research has investigated the diversity of system components beyond the host community, including predators, competitors and coinfecting symbionts. Reductions in predator diversity have been correlated with increased prevalence of Sin Nombre hantavirus in deer mice (Peromyscus maniculatus) (Dizney & Ruedas 2009; Orrock et al. 2011) and higher infectious disease levels in coral reefs (Raymundo et al. 2009; see also Rohr et al. 2015). The experimental exclusion of large herbivores in East African savanna ecosystems led to a doubling in the density of their competitors, rodents and their associated fleas (McCauley et al. 2008; Keesing & Young 2014; Young et al. 2014; but see Borer et al. 2009). "
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    ABSTRACT: Global losses of biodiversity have galvanised efforts to understand how changes to communities affect ecological processes, including transmission of infectious pathogens. Here, we review recent research on diversity-disease relationships and identify future priorities. Growing evidence from experimental, observational and modelling studies indicates that biodiversity changes alter infection for a range of pathogens and through diverse mechanisms. Drawing upon lessons from the community ecology of free-living organisms, we illustrate how recent advances from biodiversity research generally can provide necessary theoretical foundations, inform experimental designs, and guide future research at the interface between infectious disease risk and changing ecological communities. Dilution effects are expected when ecological communities are nested and interactions between the pathogen and the most competent host group(s) persist or increase as biodiversity declines. To move beyond polarising debates about the generality of diversity effects and develop a predictive framework, we emphasise the need to identify how the effects of diversity vary with temporal and spatial scale, to explore how realistic patterns of community assembly affect transmission, and to use experimental studies to consider mechanisms beyond simple changes in host richness, including shifts in trophic structure, functional diversity and symbiont composition. © 2015 John Wiley & Sons Ltd/CNRS.
    Ecology Letters 08/2015; DOI:10.1111/ele.12479 · 13.04 Impact Factor
    • "The dilution effect appears to be a common phenomenon in other hantavirus–host systems . At least 7 other studies have documented greater hantavirus prevalence in rodent communities with reduced diversity (Suzán et al. 2008; Tersago et al. 2008; Dizney and Ruedas 2009; Suzán et al. 2009; Carver et al. 2011; Voutilainen et al. 2012). Three of these studies examined SNV dynamics in the United States, 2 examined Chaclo and Calabazo hantaviruses in Panama, and 2 investigated Puumala virus in Europe. "
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    ABSTRACT: The complexity of a community can play a fundamental role in the prevalence of pathogens by altering interactions among hosts and pathogen transmission. Information on the frequency of contacts between individuals and the distribution of contact rates in a population is critical to predicting pathogen prevalence. However, contact rates are notoriously difficult to document especially in small, nocturnal species. We have been documenting the contact rates of deer mice (Peromyscus maniculatus) in nature with respect to infection with Sin Nombre virus (SNV), a zoonotic pathogen, and the biodiversity of the mammalian community. Our long-term field studies, as well as those of others, revealed that prevalence of SNV in deer mice is related to the complexity of the mammalian community such that pathogen prevalence is lower in more diverse communities. Using a combination of techniques, we found evidence that contact rates between deer mice differ with respect to biodiversity. Deer mice in more complex communities had fewer intraspecific interactions than those in less diverse communities. Contact rates of individual deer mice were highly variable with a minority of the deer mice accounting for a majority of the interactions. Infection with SNV was related to risk-taking behavior; animals categorized as “bold” were 3 times more likely to be infected than “shy” deer mice. Results of these studies have implications for pathogen management in wildlife and humans.
    Journal of Mammalogy 02/2015; 96(1):29-36. DOI:10.1093/jmammal/gyu025 · 2.23 Impact Factor
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    • "The change of rodent community structure in human-dominated landscapes could be an important driver of these outbreaks, mainly because of two factors: (1) the increase of reservoir host abundance, as there is evidence that several hantaviruses are horizontally transmitted in a density-dependent manner (Niklasson et al. 1995; Mills et al. 1999; Madhav et al. 2007); and (2) the decrease of small mammal diversity, as hantaviruses may increase their infection prevalence in rodent hosts inhabiting species-poor communities, a phenomenon called dilution effect (Keesing et al. 2006). This phenomenon, originally described for vector-borne pathogens (Keesing et al. 2006), is suggested to occur in some Old World and New World hantaviruses such as Choclo virus, Puumala virus, and Sin Nombre virus (Tersago et al. 2008; Clay et al. 2009; Dizney and Ruedas 2009; Suzán et al. 2009; Carver et al. 2011a; Voutilainen et al. 2012). Furthermore, both driving factors could operate synergistically to influence disease transmission among hosts. "
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    ABSTRACT: Rodent-borne hantaviruses are a group of zoonotic agents that cause hemorrhagic fever in humans. The transmission of hantaviruses among rodent hosts may be higher with the increase of reservoir host abundance in a given area (density-dependent transmission) and with the decrease of small mammal diversity (dilution effect phenomenon). These population and community parameters may be modified by habitat fragmentation; however, studies that focus on fragmentation and its effect on hantavirus infection risk are scarce. To further understanding of this issue, we assessed some population and community responses of rodents that may increase the risk for hantavirus transmission among wildlife hosts in the Americas. We conducted a meta-analysis of published studies to assess the responses of small mammals to fragmentation of native habitats, relative to patch size. Our analyses included five countries and 14 case studies for abundance of reservoir hosts (8 species) and 15 case studies for species richness. We found that a reduction of patch area due to habitat fragmentation is associated with increased reservoir host abundances and decreased small mammal richness, which is mainly due to the loss of non-host small mammals. According to these results, habitat fragmentation in the Americas should be considered as an epidemiological risk factor for hantavirus transmission to humans. These findings are important to assess potential risk of infection when fragmentation of native habitats occurs.
    EcoHealth 05/2014; 11(4). DOI:10.1007/s10393-014-0944-9 · 2.27 Impact Factor
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