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Links between ecological integrity, emerging infectious diseases originating from wildlife, and other aspects of human health -an overview of the literature

Links between ecological integrity, emerging
infectious diseases originating from wildlife, and
other aspects of human health - an overview of
the literature
Tom Evans, Sarah Olson, James Watson, Kim Gruetzmacher, Mathieu Pruvot, Stacy Jupiter,
Stephanie Wang, Tom Clements and Katie Jung
April 2020
The Wildlife Conservation Society saves wildlife
and wild places worldwide through science,
conservation action, education, and
inspiring people to value nature.
WCS envisions a world where wildlife
thrives in healthy lands and seas, valued
by societies that embrace and benefit
from the diversity and integrity of life on earth.
Summary 1
Introduction 2
Review of the Evidence 3
Point 1. Degradation has significantly altered ecological systems 3
Point 2. The majority of emerging infectious disease threats are
zoonotic, originate from wildlife, and often have major social and
economic impacts 4
Point 3. Ecological degradation increases the overall risk of zoonotic
disease outbreaks originating from wildlife 5
Point 4. Degradation of ecosystems also has complex effects, often
negative, on many other aspects of human health 8
Solutions and responses 9
References 12
Tom Evans, Lead, REDD+ and Forest Conservation Program,
Sarah Olson,
Associate Director of Epidemiology,
James Watson, Director, Science and Research Initiative,
As a result of the COVID-19 pandemic, there is heightened public interest in the risk factors that
lead to such events. This report contains an overview of the literature linking declines in the
integrity of ecosystems to impacts on human health, in particular the risk of emerging infectious
disease outbreaks that originate in wildlife. The review identified four key findings, as follows.
1. Degradation has significantly altered ecological systems worldwide and continues to
expand into new areas.
2. The majority of emerging infectious disease
threats are zoonotic, originate from wildlife,
and often cause major social and economic impacts.
3. Ecological degradation increases the overall risk of zoonotic disease outbreaks
originating from wildlife.
a. This relationship has been shown for multiple individual diseases, in regional
and global studies and in theoretical models, although the proportion of cases of
degradation that lead to substantially increased risk is not well understood.
a. The increased risk results from multiple interacting pathways including increased
human contact with pathogens and disruption in pathogen ecology.
b. The key “ingredients” that accentuate the risk of an emerging infectious disease
spillover event are activities (e.g., creation of new habitat edges, wildlife trade and
consumption, agricultural intensification) in areas of high biodiversity that
elevate contact rates between humans and certain high-risk wildlife species.
4. Degradation of ecosystems also has complex effects, feedback loops, and some notable
negative impacts on many other aspects of human health, including: the prevalence of
long-established (endemic) zoonotic diseases, the prevalence of vector-borne and water-
borne diseases; air quality; nutrition; mental health; and access to traditional medicines;
as well as effects on human health through the impacts of climate change.
Hence, avoiding ecosystem degradation (by keeping ecosystems as intact as possible and
avoiding the creation of high-risk interface zones and high-risk activities that increase human-
wildlife contact), combined with broader One Health
approaches that address the full range of
risk factors, will help to reduce the risk to humanity from emerging zoonoses and can have other
beneficial health outcomes as well.
Protecting ecological integrity should be a priority action within any comprehensive plan to
avoid future zoonotic outbreaks, alongside other critical measures such as ending the
commercial wildlife trade for human consumption, closing commercial wildlife markets,
building surveillance and response systems, providing global access to health care, and
mitigating disease risks associated with domestic animals.
A One Health approach, optimizing human health and ecological integrity, can be used to find
solutions for different landscape contexts (e.g. remote intact landscapes, mixed, partly natural
landscapes, and heavily human-dominated landscapes).
‘Emerging infectious diseases can be defined as infections that have newly appeared in a population or have
existed but are rapidly increasing in incidence or geographic range’ (Morse 1995).
These conclusions are based on a range of evidence types including detailed case studies, global
analyses, modelling, and broad expert consensus.
Whilst the key conclusions are clear, it is important to acknowledge that the science is still
somewhat incomplete and it is difficult to make predictions at the scale of individual
ecosystems, locations or infectious agents, especially as outbreaks are inherently rare events and
the exact relationship between pathogen dynamics and ecosystem change is often context-
specific and subject to interactions with many other environmental, socio-economic, political
and cultural factors.
In addition to lowering disease spillover risk, avoiding environmental degradation has many
related benefits, including: climate change mitigation; climate change adaptation and
environmental resilience; maintenance of watersheds and rainfall patterns; biodiversity
conservation; and the protection of the homelands and livelihoods of Indigenous Peoples and
local communities.
The devastating emergence of the virus causing COVID-19 has led to increased interest in the
factors that result in pandemics and other disease outbreaks. There is an extensive body of
literature on emerging infectious diseases that originate from wild animals, much of it built up
since the SARS epidemic of 2002-2004 raised global awareness of the topic. The wildlife trade
has been identified as one key risk factor and has rightly drawn a great deal of attention. This
review examines information relating to another commonly postulated risk factor - damage to
the integrity of ecosystems. It was developed to inform the institutional position WCS takes on
this topic, and the advice we share with our many partners around the world.
The review, whilst not intended to be a comprehensive or systematic review, considers a wide
sample of publications through to March 2020, with a focus on the peer-reviewed literature, and
draws on the combined expertise of scientific and policy staff from across WCS, including our
dedicated programs on wildlife health and on the conservation of intact forests.
In broad terms the integrity of an ecosystem is the degree of
or, equivalently, degree
of absence of human modification. A widely used definition of ecosystem integrity is 'the ability
of an ecological system to support and maintain a community of organisms that has species
composition, diversity, and functional organization comparable to those of natural habitats
within a region (Parrish et al. 2003).
Damage to the integrity of ecosystems can take many forms, including deforestation,
fragmentation, construction of linear infrastructure, mining, extraction of oil or gas, pollution,
altered fire regimes, logging and the draining or flooding of natural habitats. As described
below, such changes often increase the likelihood that humans will be exposed to unfamiliar
and sometimes deadly micro-organisms. We do not review data on the wildlife trade in detail,
but it is closely linked to the issue of ecological integrity, because so much of the wildlife trade is
associated with areas where degradation is taking place, often enabled by increases in access to
newly fragmented or exploited frontier regions. Furthermore, the loss of wildlife populations
(‘defaunation’) is itself an important form of ecosystem degradation, disrupting many ecological
Beyond the health aspects discussed here, high ecological integrity is also important for a wide
range of other critical values and benefits to humanity, as reviewed recently by Watson et al.
(2018) for forests.
Julie Larsen Maher © WCS
The following sections cover the four linked points set out in the summary.
Point 1. Degradation has significantly altered ecological systems
Humanity has been reshaping Earth’s ecosystems for millennia. We engage in large-scale
conversion of natural habitats to agricultural crops and urban areas to feed and house our
burgeoning population, and we change the state of natural systems through activities like
hunting, logging, resource extraction, infrastructure construction, recreation and fire
management. There has been a myriad of recent attempts to map the level of anthropogenic
environmental degradation across the land and ocean with some estimates showing that ~80%
of both realms have clear evidence of anthropogenic modification, varying in extent across
particular ecosystems (Venter et al., 2016; Jones et al. 2018).
The IPBES global synthesis report released in 2019 (IPBES 2019) clearly outlined the recorded
evidence of the multitude of impacts of human activity on ecological systems, including:
significantly altered global patterns of species composition and abundance,
loss and appropriation of primary productivity,
changes in land-surface hydrology and albedo,
alterations to the biogeochemical cycles of carbon, nitrogen, and phosphorus.
Many natural scientists argue that the anthropogenic degradation placed on ecosystems has
meant Earth has entered a human-dominated geological era termed the Anthropocene (Malhi et
al. 2014) and we are increasingly transgressing catastrophic environmental boundaries (Steffen
et al. 2015).
Point 2. The majority of emerging infectious disease threats are zoonotic, originate
from wildlife, and often have major social and economic impacts.
The World Organization for Animal Health (OIE) defines zoonotic diseases ‘as infectious
diseases that are naturally transmitted from vertebrate animals to humans and vice versa’ (Wang
and Crameri 2014). Emerging infectious diseases can be defined as infections that have newly
appeared in a population or have existed but are rapidly increasing in incidence or geographic
range (Morse 1995). An outbreak is the occurrence of one or more cases in a group of individuals
in a defined region. Spillover occurs when an animal pathogen successfully jumps to humans.
2a) The majority of emerging infectious disease threats are zoonotic
More than 335 emerging infectious disease outbreaks (involving 183 distinct pathogens)
were reported worldwide during 1940-2004, more than 50/decade, and the rate of
outbreaks is increasing (Jones et al. 2008).
In recent years, 52% of all emerging infectious disease events originated in wildlife.
Among emerging zoonoses specifically, 72% of outbreaks have originated in wildlife
(with the rest from domestic animals). The frequency of outbreaks originating in wildlife
is increasing. All facts under this bullet are from Jones et al. (2008).
Populations of wild animals carry a high diversity of the types of infectious agents that
could potentially jump to humans, with higher diversity of such agents where the
diversity of host animals is higher (e.g. Anthony et al. 2017). Most diseases in wild
animals remain very poorly studied, many pathogens remain unidentified, and many
spillover events are overlooked (Johnson et al. 2020).
The global connectivity of human society greatly increases the long-distance transport of
disease vectors (Tatem et al. 2006) and of animals infected with infectious pathogens
(Can et al. 2019), increasing the number of human-wildlife interfaces where pathogens
can spill over into humans. Connectivity also facilitates subsequent human-human
Less than 300 viruses from 25 high-risk viral families are known to infect people, yet
scientists have estimated there are around 1.7 million viruses from these same viral
families that are not yet discovered in mammals and birds, of which 700,000 are believed
to have zoonotic potential (Carroll et al. 2018).
2b) Economic and societal impacts of zoonotic diseases
Zoonoses of domestic and wildlife origin combined are mostly long-established as
endemic threats. The 13 top ranked zoonotic diseases by scale of impact largely fall into
this category and annually they are estimated to be responsible for over 2 million deaths
and 2 billion illnesses (ILRI 2012).
Emerging zoonoses have significant implications in terms of both public health and
economic stability, with the costs of many individual recent major outbreaks such as
SARS, MERS and Ebola reckoned in the tens of billions of US dollars and exceeding 1-2%
of GDP in less wealthy countries (GPMB 2019).
o The impact of the 2002-2004 SARS Coronavirus epidemic (774 deaths) on
tourism, food and travel in mainland China alone was estimated at US$8.5bn
(Beutels et al., 2009). The total global cost, associated with lost economic activity,
is estimated to have been around $40 billion (Knobler et al. 2004).
o The 2014 Ebola outbreak in West Africa cost an estimated US$2.2bn in GDP
alone and wiped out many of the recent development gains in Guinea, Liberia,
and Sierra Leone, which had been among the fastest growing economies in the
world (CDC, 2016; International Working Group On Financing Preparedness,
The costs of a single severe future influenza pandemic, which are also indicative of the
potential costs of a pandemic originating from wildlife, were predicted to reach US$1.5
trillion or 3.1% of global GDP for one year at 2006 prices (Burns et al. 2006), whilst the
annualized cost to the global economy of occasional severe pandemics averaged over
long periods was estimated at $80-$500 bn/year (up to 0.6% of global GDP) depending
on whether or not deaths were ascribed an economic cost (Fan et al. 2018).
Recent estimates suggest that the cost of the unfolding COVID-19 pandemic to the world
economy, in purely monetary terms, will be US$1-2 trillion, possibly more (UNCTAD
2020), with huge additional costs to human life and wellbeing.
Point 3. Ecological degradation increases the overall risk of zoonotic disease
outbreaks originating from wildlife
There are multiple interacting lines of evidence that support this conclusion, which is reflected
in numerous recent reviews of the topic (e.g. Patz et al. 2004, Karesh et al. 2012, Gottdenker et al.
2014, Murray et al. 2016, UNEP 2016, Watson et al. 2018, DiMarco et al. 2020). The issue is also
reflected in the recently issued ‘Berlin Principles on One Health’ white paper
The land-use changes
that tend to elevate disease risk include deforestation, forest degradation
(e.g. through logging), fragmentation, expansion of infrastructure (e.g. roads, railways,
powerlines, dams), changes in drainage, and hunting and capture for trade (Patz et al. 2004, Loh
et al. 2015). Risks are further multiplied by large movements of human populations, agricultural
intensification near to natural areas, and climate change, among other factors (Gebreyes et al.
2014, Karesh et al. 2012).
The main lines of evidence summarized below are (a) case studies, (b) global/regional analyses
and (c) theoretical modelling. They point to (d) a range of different pathways or mechanisms by
which the effects take place.
Case studies
Multiple examples of zoonotic disease outbreaks from wildlife have been reported in the
literature as being associated with forest degradation, human encroachment on forests, and
wildlife trade chains that connect biodiverse forests to markets:
SARS and COVID-19. The evolutionary host of the SARS virus (SARS-CoV) and the
closely-related COVID-19 virus (SARS-CoV-2) are bats and in both cases, index cases
were associated with wildlife markets. It is thought that SARS-CoV passed through civets
(wild or farmed) before infecting humans and it is unknown at this stage if SARS-CoV-2
also passed through an intermediate host (Hu et al. 2017; Lu et al. 2020; Li et al., 2006).
Here the main issue is the volume, mixing, unsanitary conditions, and overcrowding of
wildlife that brought a bat virus into contact with a variety of animals in wildlife trade
chains originating in natural habitats and ending at urban markets.
Following the infectious disease literature, the term 'land-use change' is used here in a broad sense to include
both damage to ecosystems (often called degradation) and ecosystem cover loss (e.g. deforestation)
Hendra virus. In Australia, science suggests declining eucalyptus habitat has altered
flying fox foraging behaviour and increased spillover risk of Hendra virus to humans
(Giles et al. 2018).
Nipah virus in Malaysia. The emergence of Nipah virus in 1998 is linked to the ecology
of bats in changing landscapes. During this time period, Pteropid fruit bats experienced a
large reduction of flowering and fruiting trees as a result of slash and burn deforestation
and an ENSO-linked drought. This led to these bats ranging into cultivated fruit orchards
that adjoined pig farms which had recently expanded into forest-edge situations (Chua et
al. 2002).
Nipah virus in Bangladesh. Case villages with Nipah virus spillovers had higher human
population density than control villages and more forest fragmentation than other parts
of the country. The number of bat roosts increased with fragmentation and was thought
to be associated with home gardens of diverse fruit trees that may provide a more
reliable food source than nearby intact forests (Hahn et al. 2014).
Ebola. In Central Africa, an association was found between Ebola outbreaks and fine-
scale measures of forest fragmentation, consistent with suspected transmission pathways
from forest-dwelling bats to forest-edge human communities (Rulli et al. 2017,
Wilkinson 2018).
HIV. Human viruses responsible for AIDS have resulted from at least four cross-species
spillovers of simian immunodeficiency viruses involving the Sooty mangabey,
chimpanzee, and western gorilla, all of which live in extensive forests. These lentiviruses
can penetrate mucous membranes so it is believed contact with ape bodily fluids
associated with the hunting, butchering and consumption of animals in trade led to the
spillovers. One of these transmission events, likely occurring between 1910 and 1930,
gave rise to the HIV strain behind pandemic AIDS (Sharp and Hahn, 2011).
Malaria in Malaysia. In Malaysian Borneo the main vector is
Anopheles leucosphyrus
and the malaria parasite is
Plasmodium knowelsi
, which primarily infects macaques.
Since 2004 it appears deforestation has altered the dynamics of the entire system,
impacting vector habitats as well as abundance and distribution of macaques and
humans. Cleared land within 1 km and deforestation within 4-5 km of households
influenced vector abundance and high historical forest loss is correlated with higher
incidence of infections (Fornace et al. 2016; Brock et al. 2019).
Lyme disease. In this system, home of the ‘dilution effect’, one reservoir host, the white-
footed mouse, is more competent at transmitting the bacteria that causes Lyme disease to
ticks than other small-mammal hosts (which therefore provide a
dampening or ‘dilution’ effect). The larval and nymphal ticks feed non-selectively so
changes in host composition end up impacting human disease risk. In the presence of
fragmentation, the white-footed mice are more abundant for the larval and nymphal
ticks to feed on (and white-tailed deer are also more abundant for the adult ticks to feed
on). Hence when biodiversity is lost, resilient species like the mouse are more prevalent,
more ticks take more blood meals from the mice and subsequently have higher
prevalence of the bacteria that causes Lyme disease (Keesing et al. 2009, Turney et al.
Global and regional analyses
There are few truly global-scale quantitative analyses of the relationship between emerging
infectious disease risk and land-use change, but those large-scale studies that do exist
support the conclusion that large-scale disturbance of ecosystems is associated with
increased risk of spillover events.
During 1940-2004 34% of emerging zoonoses were believed to be associated primarily
with either land-use change or activities relating to bushmeat (Loh et al. 2015, UNEP
Mapping outbreaks globally suggests that land-use change in tropical forest regions is
one of the key risk factors associated with disease spillovers from wildlife into humans
(Allen et al. 2017).
Two regional multi-pathogen studies present strongly suggestive evidence that
biodiversity decline and loss of ecosystem integrity play a role in driving zoonotic
outbreaks, for the Asia-Pacific (Morand et al. 2014) and for Australia (McFarlane et al.
The number of zoonotic diseases found in different wildlife species varies depending on
a number of factors, including some which relate to threats to the ecosystems that they
occupy. For example, more zoonotic diseases are found in threatened species facing
declines in their habitat, or high pressure from exploitation, compared to those
threatened for other reasons (Johnson et al. 2020).
Following biodiversity loss, abundant species with no extinction risk and increasing
populations (e.g. adaptable or ‘weedy’ species that thrive in heavily modified landscapes) are
also significant carriers of zoonoses, indicating that degradation of intact ecosystems is not
the only pathway to increasing the risk of wildlife-human transmission (Johnson et al. 2020,
Keesing 2010, Salkeld et al. 2013).
Theoretical modelling
Several recent modelling studies provide theoretical support to the plausibility of increased
spillover risk being linked to ecosystem degradation (e.g. Myers et al 2013, Gortazar et al.
2014, Faust et al. 2018, Wilkinson et al. 2018, Borremans et al. 2019).
Across these various lines of evidence, several multiple interacting pathways are known or
suspected to lead to increased risk of disease transmission. These include:
Increased contact between humans, livestock and pathogens along newly created edges
o These edges represent areas where newly arrived human and livestock
populations without immunity mix with unfamiliar pathogens, with contacts
sometimes further increased by the movement of host species in response to the
disrupted ecology of their habitat (Bloomfield et al. 2020, Brownstein et al. 2005,
Johnson et al. 2020, da Silva-Nunes et al. 2008). Fragmentation has placed over
70% of the world’s forests within 1 km of an edge (Haddad et al 2015) and is
worsening across the tropics (Taubert et al. 2018).
Increased contact with humans along wildlife trade chains.
o Much wildlife trade originates from recently opened frontier areas where
populations have not yet been significantly depleted by over-harvest. There is
abundant evidence that large trade volumes, mixing of diverse species, and poor
hygiene practices expose people all along these trade chains to increased risk of
infection (Bloomfield et al. 2020, Greatorex et al. 2016, Pruvot et al. 2019).
Changes to pathogen abundance due to changes in host abundance, diversity and
o Degradation can cause increases in the local populations of host or vector species,
raising the chance of transmission. Habitat damage can also place individuals
under increased stress, making them more susceptible to infections (Levi et al.
2012, Civitello et al. 2015, Rulli et al. 2017, Olson et al. 2010, Vittor et al. 2006,
Rapid evolution/mutation of pathogens due to novel conditions and novel hosts is also
suspected to be a contributory factor (Zohdy et al. 2019).
It is also possible that changes in the biodiversity within ecosystems (e.g. extinctions or local
extirpations of some species) can alter the likelihood of diseases being transmitted among the
remaining species (‘dilution’ and ‘amplification’ effects), although there is insufficient evidence
to confirm how common these alternative patterns are (Keesing et al. 2009, Randolph & Dobson
2012). It is well known for Lyme disease (see above) but has been looked for in other disease
systems (Hanta virus and West Nile virus) with mixed results (Suzan et al. 2009; Luis et al. 2018;
Tran et al. 2017; Koenig et al. 2010; Salkeld et al. 2013).
Point 4. Degradation of ecosystems also has complex effects, often negative, on many
other aspects of human health
Vector-borne and parasitic disease
There are several studies of the prevalence of non-zoonotic vector-borne disease in relation to
ecosystem change. Some show increases, others do not:
The Amazon
. Deforestation has altered mosquito ecology, resulting in more
larval breeding habitat and higher human biting rates of
Anopheles darlingi
which is a highly competent vector for the more deadly falciparum malaria. This
phenomenon is ephemeral and occurs at the frontier of deforestation events
where new human migrants are also arriving.
. Although data were too limited to take a longitudinal approach, the latest
data-rich assessment at multiple scales and using a pre-registered hypothesis
testing approach (which makes it less subject to selective interpretation) shows no
relationship between deforestation and malaria in Africa. Differences between
Africa and the Amazon are attributed to the fact that forest-human associations in
Africa are long-standing, and do not involve human migration to a deforestation
frontier (Bauhoff & Busch 2020). There are a few local ecological studies from
Kenya that suggest deforestation increases vectorial capacity of
through changes in microclimates that influence sporogonic
development and mosquito reproductive fitness (Afrane et al. 2006, 2008).
Schistosomiasis. In one studied region, dam construction degraded freshwater
ecosystems and led to local extirpation of native prawns. Restoration of these prawns,
which are ‘voracious predators of the snail intermediate hosts for schistosomiasis’,
reduced snail host abundance and as a result, human schistosomiasis prevalence
(Sokolow et al. 2017; Sokolow et al. 2015).
In one community, after adjusting for access to care, health district size,
and spatial trends, a 4.3% increase in deforestation was associated with a
48% increase of malaria incidence (Olson et al. 2010, Vittor et al. 2009, 2006).
Water-borne disease
There are examples of water-borne bacterial disease increases associated with ecosystem
Diarrheal disease in children. There is a significant association between tree cover in
upstream watersheds and probability of diarrheal disease among rural children under
age 5, as measured from a dataset from 35 developing countries. The effect of a 30%
increase in upstream tree cover is similar to the effect of improved sanitation (Herrera et
al. 2017).
Typhoid occurrence. Fragmentation of riparian forests and density of roads crossing
creeks within a watershed is significantly related to incidence of typhoid in Fiji (Jenkins
et al. 2016).
Other established connections between environmental degradation and human health effects
include air quality, nutrition, pharmaceuticals and biomedical discoveries, mental health, access
to traditional medicines, endemic zoonotic diseases, and indirect effects on human health
through the impacts of climate change. More detailed coverage of these topics can be found in
the broad reviews by ILRI (2012), Romanelli et al. (2015), Rohr (2019), Kilpatrick (2017), and
Whitmee et al. (2015).
Guide in the Budongo Forest, Uganda, Julie Larsen Maher © WCS
As described above, there are multiple clear lines of evidence pointing towards the conclusion
that declines in the integrity of ecosystems increase the global risk of zoonotic disease spillovers,
and hence the risk of pandemics. Enough is already known to identify the broad steps needed to
ensure that our interactions with nature occur in a way that lowers pandemic risk. It should be
acknowledged that the science is not complete and there are important questions to answer
before we know everything that we would ideally wish to know around the linkages between
the integrity of ecosystems and emerging zoonotic diseases. However, the precautionary
principle necessitates that strong action is taken while this additional research is undertaken
The One Health framework, adopted and championed by WHO, FAO, OIE, the Centers for
Disease Control, the World Bank, WCS and many other organizations and institutions, is a
widely applied approach to address zoonotic challenges (Waltner-Toews 2017; Gebreyes et al.
2014). The core One Health principle is that ‘communicable and non-communicable diseases
demand a truly comprehensive understanding of health and disease, and thereby a unity of
approach that is achievable only through convergence of human, domestic animal, wildlife,
plant, and environmental health, on a planetary scale’. One Health should be used as an
umbrella framework to find convergence among ecological and human health challenges. The
Berlin Principles
state, ‘going forward...we must overcome sectoral and disciplinary silos; apply
adaptive, forward reasoning, and implement multidisciplinary and multilateral solutions, while
boldly integrating current uncertainties to address the opportunities and challenges ahead’.
Ecological changes are important factors in driving disease outbreaks and as such need
increased levels of attention at international, national and local levels. One Health approaches
relating to the integrity of ecosystems must be placed in the context of how much land
degradation has already occurred in an area, and the ‘three conditions’ described by Locke et al.
(2019) are one useful way to frame these solutions. This framing recognises that there have been
diverse human influences on the Earth’s surface and it is possible, at least broadly, to categorize
landscapes by integrating nature-centric (what remains of nature) and human-centric (human
land-use) assessments of drivers and pressures on biodiversity. Three broad conditions
large, intact, mostly natural areas;
‘shared’, partially natural landscapes;
farms and cities with very limited natural space remaining
According to each condition, broad suites of responses can be proposed to improve the state of
ecosystem integrity, to secure nature’s contributions to people, and minimise the risk of future
pandemics. These responses are outlined below. To be achieved, they need to be placed in the
appropriate policy, regulatory and legal frameworks, be supported by finance, engage the full
range of stakeholders in effective ways and be supported by additional science. It is beyond the
scope of this paper to discuss these critical aspects of implementation in detail.
In large wild landscapes we need to retain ecosystem integrity to the greatest extent possible as
by doing this we will minimize the various pathways that increase the risk of pandemics and
other spillover events.
Maintaining ecosystem integrity means not modifying ecosystems beyond their natural
range of variation, which in practice means avoiding the expansion of large scale
extractive uses (e.g. industrial logging, large-scale harvest of animal and plant products),
not fragmenting areas with infrastructure, pastures and farmland, and not disrupting
natural fire and flood regimes.
Since many of these areas are inhabited by, and protected by, Indigenous Peoples and
local communities, we must strengthen health care infrastructure to meet the needs of
these populations, and enhance emerging infectious disease surveillance in collaboration
with them (Munster et al. 2018) as well as better understanding the patterns of exposure
and immunity that they experience.
In shared landscapes we need to manage significant ongoing levels of contact between humans,
wildlife and livestock, and be aware of factors (e.g. changing farm practices) that may increase
these levels. In this context we should consider nature-based or ‘One Health’ solutions that
support both human health and the restoration of ecosystem integrity to the fullest extent
Solutions that benefit both human health and environmental targets have the
advantage of contributing to multiple Sustainable Development Goals. A broad
recommendation for shared landscapes is that infectious disease interfaces and pathways that
have been created must either be removed or mitigated.
Forest edges are an example of an interface that can be reduced in extent in some
settings, e.g. through restoration that reduces fragmentation.
In other settings forest edge contact zones may be a part of the landscape that cannot be
reduced, in which case the focus should be on mitigating the risks they present.
The commercial wildlife trade is an example of a high-risk interface that can and should
be removed in many cases, and whose risks should be mitigated in the remaining cases.
Where restoration is not attainable, management decisions should nonetheless avoid
any further degradation of ecological systems
In the ‘third condition’ of the Locke et al. (2019) framework - highly human-dominated, farmed
and urban areas - there remain zoonotic diseases originating from wildlife, such as rabies from
bats or skunks, West Nile virus from birds via mosquito vectors, as well as tularemia, plague, and
hantavirus. Alongside these, such areas are also risky areas for emerging infectious disease
outbreaks from wildlife due to connections between remote source areas and urban and peri-
urban centres of demand for the wildlife trade.
In these areas, commercial wildlife trade, particularly for human consumption, should
be halted and other forms of domestic animal trade should be improved to ensure
excellent hygiene standards. Public health, biosecurity and disease surveillance and
response systems tend to be more robust for known pathogens in these places, but
defences are less robust for the new, emerging pathogens that also occur in commercial
wildlife markets.
Julie Larsen Maher © WCS
see e.g. the Berlin Principles and IUCN’s new standards for Nature-based Solutions
For example, an intervention used after the discovery of Marburg, and Bombali and Zaire Ebolaviruses in West
Africa was as simple as information and resources on how to exclude insectivorous bats from homes and cover
food sources In the case of Nipah virus in Bangladesh, a
simple tree skirt can prevent bats from urinating in vessels that are used to collect tree sap (Khan et al 2012).
Afrane et al. (2006) Effects of microclimatic changes caused by deforestation on the survivorship and
reproductive fitness of
Anopheles gambiae
in western Kenya Highlands.
Am J Trop Med Hyg.
Afrane et al. (2008) Deforestation and vectorial capacity of
Anopheles gambiae
Giles mosquitoes in
malaria transmission, Kenya.
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Anthony et al. (2017) Global patterns of coronavirus diversity.
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Bauhoff and Busch (2020) Does deforestation increase malaria prevalence? Evidence from satellite
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... Examples include the Ebola virus, yellow fever, malaria, Zika virus, and coronaviruses (Guerra et al. 2006;Wilcox and Ellis 2006;Karjalainen et al. 2010;Monath and Vasconcelos 2015;Olivero et al. 2017). Evidence suggests that conserving tropical forests and sustaining their high levels of biodiversity can decrease transmission of some infectious diseases (Evans et al. 2020;UNEP 2020). ...
... When native biodiversity is lost, ecosystems often become more vulnerable to disturbance and become less reliable-and less effectiveat providing vital services. Habitat fragmentation in highly biodiverse areas can even lead to spillover of pathogens from wildlife reservoirs to human hosts (Borremans et al. 2019;Evans et al. 2020). It is uncertain how much biodiversity loss can be sustained before ecosystems see major loss of function (Dirzo et al. 2014; Moore 2018). ...
... Deforestation may play a role in the spread of emerging infectious diseases as well as outbreaks of established vector-borne disease (Evans et al. 2020;Guégan et al. 2020): ...
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Better Forests, Better Cities evaluates how forests both inside and outside city boundaries benefit cities and their residents, and what actions cities can take to conserve, restore and sustainably manage those forests. This report is the first of its kind comprehensive resource on the connection between cities and forests, synthesizing hundreds of research papers and reports to show how all forest types can deliver a diverse suite of benefits to cities.
... This is because environmental health is linked to human health. A number of recent scientific studies point to a link between the conversion of natural ecosystems, increased human contact with wildlife, the emergence of new (and the spread of old) zoonotic diseases, and epidemics (or even pandemics) harming human health [26]. Examples include Ebola, coronaviruses, Marburg, Zika, and malaria [27,28] (Box 9.3). ...
... Deforestation and forest degradation-and exploitation of wild animalsare implicated in the emergence over the past few decades of zoonotic disease outbreaks such as Ebola, SARS, avian flu, and COVID-19 [26]. One study found that Ebola outbreaks in Central and West Africa were significantly associated with forest losses in the previous two years [70]. ...
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China’s economic rise over the past 40 years is one of the major transformational events in modern world history. China has lifted more than 850 million people out of poverty since 1978.
... An increasing threat in urbanizing areas is zoonosis since wildlife can spread diseases to both people and domestic animals [9,[15][16][17]. The rise of the One Health framework acknowledges the threat of vector-borne diseases and underscores how the interconnections between people, animals, plants, and the environment significantly impact human health, especially in urbanizing regions, where increasing contact between people and animals can spread diseases such as rabies, the West Nile virus, and the coronavirus [16,18,19]. ...
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Negative interactions between people and wildlife pose a significant challenge to their coexistence. Past research on human–wildlife interactions has largely focused on conflicts involving carnivores in rural areas. Additional research is needed in urban areas to examine the full array of negative and positive interactions between people and wildlife. In this study, we have conducted interviews in the desert metropolis of Phoenix, Arizona (USA), to explore residents’ everyday interactions with wildlife where they live. Our multifaceted approach examines interactions involving physical contact and observational experiences, as well as associated attitudinal and behavioral responses and actions toward wildlife. Overall, the qualitative analysis of residents’ narratives identified two distinct groups: people who are indifferent toward wildlife where they live, and those who appreciate and steward wildlife. Instead of revealing conflicts and negative interactions toward wildlife, our findings underscore the positive interactions that can foster human wellbeing in urban areas. The holistic approach presented herein can advance knowledge and the management of coexistence, which involves not only managing conflicts but also tolerance, acceptance, and stewardship. Understanding diverse human–wildlife interactions and managing coexistence can advance both wildlife conservation and human wellbeing in cities.
... Several studies have shown that 75% of the infectious diseases that threaten the human health and economic stability are caused by the trade and consumption of wildlife (Jones et al., 2008;Lu et al., 2020;Miguel et al., 2020;Smith et al., 2017;Taylor et al., 2001). Wildlife is an important component of the pathogen transmission system, as demonstrated by the COVID-19, MERS, SARS, and other significant infectious diseases (Cohen, 2020;Cox-Witton et al., 2021;Evans et al., 2020;Lloyd-Smith et al., 2009). ...
The association between the COVID‐19 pandemic and the wildlife trade in the seafood market in Wuhan has raised public concern regarding wildlife consumption and public health safety. Considering several coronavirus transmission incidents related to aquatic products and the location of wild freshwater fish in aquatic consumption in China, the effects of COVID‐19 on the purchase intention of wild freshwater fish was investigated. Based on 1163 online questionnaires from eight provinces (including two province‐level municipalities) in the Yangtze River Basin, ordered logistic regression was carried out to analyze the influencing factors of purchase intention of wild freshwater fish during the COVID‐19 pandemic. The empirical results indicated that the COVID‐19 pandemic had changed consumers' perceived risk and purchase frequency of wild freshwater fish. External stimulus caused by the COVID‐19 pandemic had little influence on perceived risk and purchase intention. Consumer preference had a significant impact on perceived risk and purchase intention. Therefore, efforts should be put to strengthen the popularization of aquatic product knowledge, guide the public to develop scientific and civic eating habits, and improve the traceability system of aquatic products. [EconLit Citations: D12‐Consumer Economics: Empirical Analysis, Q22‐Fishery; Aquaculture].
... As defined by the Centers for Disease Control (CDC), emerging infectious diseases (EIDs) are "those whose incidence in humans has increased in the past two decades or threaten to increase in the near future" Centers for Disease Control (2018 (Evans et al., 2020). Zoonoses can be deadly or have lasting effects throughout the lifetime of people who are infected. ...
... Wildlife diseases pose serious risks to human and livestock health (Morens et al., 2004;Jones et al., 2008). Between 1995 and 2008, most infectious diseases globally (75%) originated from wildlife, also having a high economic impact exceeding $120 billion (Jones et al., 2008), and even today most emerging infectious diseases found in humans originate from wildlife (Evans et al., 2020). ...
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The analysis of stable isotopes in different tissues has been widely used to obtain information on the ecology and nutritional patterns of wildlife. The isotope ratios of the stable isotopes of carbon and nitrogen (δ¹³C and δ¹⁵N) analysed in different tissues are directly related to the animal's diet and, to some extent, to the environment where the individual has growth. Specifically, this type of analysis in hair samples has become relevant as it provides information on the quality and long-term composition of the diet that produced the isotope accumulation during the tissue growth. We took samples of wild boar (Sus scrofa) hair from 7 different populations in the south-west of Spain (Mediterranean habitats), in the 2018/2019 hunting season. The main objectives of this study were (i) to investigate the use of hair stable isotopes to reveal differences in composition and quality of the diet of wild boar within the same population or between populations, and (ii) to use hair isotopes as a tool to uncover hidden management practices that may occur in hunting areas associated with the use of supplementary feeding or even captive breeding and release. Each animal had a hair (long 10 cm) analysed in duplicate, previously cut into parts of equal size (from the oldest part of the hair to the most recent part), that were analysed separately. We found differences in δ¹³C and δ ¹⁵N between hair parts and populations, which can be related to management actions at different times during the hair growth. Moreover, the use of corn, a type of plant not occurring naturally in the study area, can be documented with the isotope analysis to prove unauthorized supplementary feeding or captive origin of wild boar in hunting areas.
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Introducció Cal que tinguem clar, en primer lloc, que en una pandè-mia no es transmet una malaltia sinó un paràsit que pro-voca una malaltia. És per això que necessitem conèixer les característiques estructurals i funcionals i el cicle de vida del paràsit i també dels seus hostes. Hem de saber com, on i en quines condicions prolifera el paràsit i com i quan es transmet entre els hostes, que poden ser de diverses espè-cies. Alguns hostes poden desenvolupar la malaltia i altres no. Els que no, de vegades, poden fer de reservoris on el paràsit persisteix sense que el detectem. Així doncs, sem-pre hi ha una xarxa complexa de relacions, ja que el que tenim és un procés dins d'un ecosistema, en el qual s'alteren dinàmiques poblacionals de diverses espècies per les relacions entre elles i en funció també de condicions variants del medi fisicoquímic. La dinàmica de la relació paràsit-hoste, al llarg del temps, dona lloc a processos evo-lutius i ecològics en el marc dels ecosistemes i els canvis en els ecosistemes de vegades alteren la relació paràsit-hoste. En conseqüència, no podem limitar-nos a estudiar les re-lacions entre el paràsit i nosaltres. En la pandèmia actual s'ha vist que el virus pot infectar felins (gats, tigres i lleons en zoos), cànids, mustèlids, primats, etc. És segur que el seu origen és zoonòtic. Es dubta si ve dels pangolins, si aquests van ser només intermediaris d'un virus de ratpe-nat, etc. S'investiga si alguna espècie o algunes persones poden esdevenir reservoris permanents. No es coneix bé l' efecte dels canvis estacionals sobre l'activitat del paràsit. El focus principal d'interès sí que és la relació entre el paràsit i nosaltres, però el problema sanitari no es pot re-soldre sense considerar aspectes no sols mèdics sinó tam-bé veterinaris i ecològics. Nota: aquest article és una versió actualitzada i ampliada d'un text encarregat per l'Institut d'Estudis Catalans el febrer de 2021 arran de la celebració de les Jornades de debat covid-19. A més, s'ha demostrat que l'afectació de la infecció en humans varia amb l' edat, l' estat de salut, la genètica, els comportaments i les condicions socials, etc., i que l'im-pacte econòmic és molt important. Tot el socioecosis-tema global en les seves múltiples dimensions, incloses les cultu rals, és trasbalsat per les pandèmies, com estem veient. Els estudis fets sobre epidèmies del passat (en humans o en plantes i animals, que han tingut efectes socials enormes) també ens mostren que les societats humanes solen respondre inicialment amb la negació del perill o el seu menysteniment, per passar després a altres respostes de resignació, pànic, cerca de "culpables" a qui carregar els neulers per distreure dels errors o males decisions de govern, etc. Així que als aspectes purament biològics i ecològics s'hi han d'afegir els econòmics, psicològics, d' es-tructura social i de govern. Causes de l'augment del risc de pandèmies Per situar la pandèmia en el context ecològic actual, cal dir que: a) La possibilitat d'una pandèmia era temuda i havia es-tat anunciada per l'Organització Mundial de la Salut (OMS) i altres veus expertes; d' epidèmies n'hem tingut sempre, però hi ha una colla de malalties emergents 1 que són infeccioses. En diem emergents perquè han augmentat la seva àrea de distribució o la seva inci-dència, com en els casos de la malaltia de Lyme, la tu-berculosi o les causades pel virus del Nil occidental o del virus Nipah; de les quals han evolucionat, com les causades per noves soques del virus de la grip, les mu-tacions del plasmodi de la malària o les que produeixen paràsits que han augmentat la seva resistència als medi-caments, com els bacteris hospitalaris superresistents; i, finalment, les malalties descobertes recentment, com les causades pel virus Hendra, el de l'Ebola o el de la covid-19, que és un virus del tipus SARS 2. En un es-tudi de 335 brots de malalties emergents 3 s'ha vist que hi predominaven les zoonosis (60,3% dels brots), de les quals el 71,8% procedien d'animals salvatges. b) La raó immediata d'aquests temors entre els experts era l'aparició cada cop més freqüent de brots epidèmics ori
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The excessive use of antibiotics has led to the emergence of resistant bacteria, mainly from the Enterobacterales group, with high pathogenic/zoonotic potentials that can lead to problems in public health. The increasing presence in freshwater ecosystems highlights the need to evaluate potential sentinel species as risk indicators for both ecosystem and human health. The freshwater mussels provide several ecosystem services, may represent potential sentinel species due to their ability to filter water and retain both organic and inorganic particles. We tested the capability of U. mancus to retain Escherichia coli as a model bacterial organism. Under experimental conditions, the mussels could clear suspended E. coli, facilitating its rapid elimination from water within the first 24 h after exposure. The species also presented a maximum retention time of 4 days. We also provide allometric equations correlating the filtering capacity with the length and the weight of mussel body parts often used in biometric studies. We provide a first assessment of the potential of the bivalve Unio mancus to act as a sentinel species for the detection of Enterobacterales and demonstrate the ability to act as a water cleaner.
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An important driving force for the rapid development of China’s economy is rapid urbanization. In 1949, only 10.6% of China’s population lived in cities. In 2019, China’s urbanization level reached 60.6%. According to the experience of industrialized countries, it is estimated that by 2035, about 70% of China’s population will live in urban areas. In 2050, this proportion will rise to around 80%.
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The ocean is fundamentally important for humankind. Simply stated, the ocean helps us breathe, regulates our global climate, and slows down the rate of global warming by absorbing 40% of anthropogenic carbon dioxide.
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Emerging infectious diseases in humans are frequently caused by pathogens originating from animal hosts, and zoonotic disease outbreaks present a major challenge to global health. To investigate drivers of virus spillover, we evaluated the number of viruses mammalian species have shared with humans. We discovered that the number of zoonotic viruses detected in mammalian species scales positively with global species abundance, suggesting that virus transmission risk has been highest from animal species that have increased in abundance and even expanded their range by adapting to human-dominated landscapes. Domesticated species, primates and bats were identified as having more zoonotic viruses than other species. Among threatened wildlife species, those with population reductions owing to exploitation and loss of habitat shared more viruses with humans. Exploitation of wildlife through hunting and trade facilitates close contact between wildlife and humans, and our findings provide further evidence that exploitation, as well as anthropogenic activities that have caused losses in wildlife habitat quality, have increased opportunities for animal-human interactions and facilitated zoonotic disease transmission. Our study provides new evidence for assessing spillover risk from mammalian species and highlights convergent processes whereby the causes of wildlife population declines have facilitated the transmission of animal viruses to humans.
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ContextDeforestation and landscape fragmentation have been identified as processes enabling direct transmission of zoonotic infections. Certain human behaviors provide opportunities for direct contact between humans and wild nonhuman primates (NHPs), but are often missing from studies linking landscape level factors and observed infectious diseases.Objectives Our objective is to better understand landscape and livelihood factors influencing human-NHP contact in rural communities whose landscapes undergo deforestation. We investigate core loss and edge density within a buffered area around survey respondent households to identify which landscape changes and behaviors increase the risk of human-NHP contact.Methods Behavioral survey data were collected from small-scale agriculturists living near forest fragments around Kibale National Park in western Uganda. We combined spatially explicit behavioral data with high-resolution satellite imagery. Using land cover classification and change detection, we investigated the relationships between forest loss and fragmentation, behavioral data, and human-NHP contact using logistic regression.ResultsBetween 2011 and 2015, there were differences in the landscape metrics around the households of individuals who had experienced human-NHP contact compared to those who had not had contact. Increased edge density around households, collection of small trees for construction, and foraging and hunting for food in forested habitat significantly increase the likelihood of human-NHP contact.Conclusion This study provides empirical evidence that forest landscape fragmentation and certain smallholders’ behaviors in forest patches jointly increase the likelihood of human-NHP contact events. Combining spatially explicit data on land use and human behaviors is crucial for understanding the social and ecological drivers of human-NHP contact.
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Deforestation can increase malaria risk factors such as mosquito growth rates and biting rates in some settings. But deforestation affects more than mosquitoes—it is associated with socio-economic changes that affect malaria rates in humans. Most previous studies have found that deforestation is associated with increased malaria prevalence, suggesting that in some cases forest conservation might belong in a portfolio of anti-malarial interventions. However, previous peer-reviewed studies of deforestation and malaria were based on a small number of geographically aggregated observations, mostly from the Brazilian Amazon. Here we combine 14 years of high-resolution satellite data on forest loss with individual-level and nationally representative malaria tests for more than 60,000 rural children in 17 countries in Sub-Saharan Africa, where 88% of malaria cases occur. Adhering to methods that we pre-specified in a pre-analysis plan, we used multiple regression analysis to test ex-ante hypotheses derived from previous literature. Aggregated across countries, we did not find either deforestation or intermediate levels of forest cover to be associated with higher malaria prevalence. In nearly all (n = 78/84) country-year-specific regressions, we also did not find deforestation or intermediate levels of forest cover to be associated with higher malaria prevalence. However, we can not rule out associations at the local scale or beyond the geographic scope of our study region. We speculate that our findings may differ from those of previous studies because deforestation in Sub-Saharan Africa is largely driven by the steady expansion of smallholder agriculture for domestic use by long-time residents in stable socio-economic settings where malaria is already endemic and previous exposure is high, while in much of Latin America and Asia deforestation is driven by rapid clearing for market-driven agricultural exports by new frontier migrants without previous exposure. These differences across regions suggest useful hypotheses to test in future research.
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Pathogen spillover between different host species is the trigger for many infectious disease outbreaks and emergence events, and ecosystem boundary areas have been suggested as spatial hotspots of spillover. This hypothesis is largely based on suspected higher rates of zoonotic disease spillover and emergence in fragmented landscapes and other areas where humans live in close vicinity to wildlife. For example, Ebola virus outbreaks have been linked to contacts between humans and infected wildlife at the rural-forest border, and spillover of yellow fever via mosquito vectors happens at the interface between forest and human settlements. Because spillover involves complex interactions between multiple species and is difficult to observe directly, empirical studies are scarce, particularly those that quantify underlying mechanisms. In this review, we identify and explore potential ecological mechanisms affecting spillover of pathogens (and parasites in general) at ecosystem boundaries. We borrow the concept of ‘permeability’ from animal movement ecology as a measure of the likelihood that hosts and parasites are present in an ecosystem boundary region. We then discuss how different mechanisms operating at the levels of organisms and ecosystems might affect permeability and spillover. This review is a step towards developing a general theory of cross-species parasite spillover across ecosystem boundaries with the eventual aim of improving predictions of spillover risk in heterogeneous landscapes. This article is part of the theme issue ‘Dynamic and integrative approaches to understanding pathogen spillover’.
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Infectious diseases are emerging globally at an unprecedented rate while global food demand is projected to increase sharply by 2100. Here, we synthesize the pathways by which projected agricultural expansion and intensification will influence human infectious diseases and how human infectious diseases might likewise affect food production and distribution. Feeding 11 billion people will require substantial increases in crop and animal production that will expand agricultural use of antibiotics, water, pesticides and fertilizer, and contact rates between humans and both wild and domestic animals, all with consequences for the emergence and spread of infectious agents. Indeed, our synthesis of the literature suggests that, since 1940, agricultural drivers were associated with >25% of all - and >50% of zoonotic - infectious diseases that emerged in humans, proportions that will likely increase as agriculture expands and intensifies. We identify agricultural and disease management and policy actions, and additional research, needed to address the public health challenge posed by feeding 11 billion people.
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Trade of bushmeat and other wildlife for human consumption presents a unique set of challenges to policy-makers who are confronted with multiple trade-offs between conservation, food security, food safety, culture and tradition. In the face of these complex issues, risk assessments supported by quantitative information would facilitate evidence-based decision making. We propose a conceptual model for disease transmission risk analysis, inclusive of these multiple other facets. To quantify several processes included in this conceptual model we conducted questionnaire surveys with wildlife consumers and vendors in semi-urban centers in Lao People's Democratic Republic (Lao PDR, Laos) and direct observations of consumer behaviors. Direct observation of market stalls indicated an estimated average of 10 kg bushmeat biomass per stall per hour. The socio-demographic data suggested that consumption of bushmeat in urban areas was not for subsistence but rather driven by dietary preference and tradition. Consumer behavioral observations indicated that each animal receives an average of 7 contacts per hour. We provide other key parameters to estimate the risk of disease transmission from bushmeat consumption and illustrate their use in assessing the total public health and socio-economic impact of bushmeat consumption. Pursuing integrative approaches to the study of bushmeat consumption is essential to develop effective and balanced policies that support conservation, public health, and rural development goals.
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The complex transmission ecologies of vector-borne and zoonotic diseases pose challenges to their control, especially in changing landscapes. Human incidence of zoonotic malaria (Plasmodium knowlesi) is associated with deforestation although mechanisms are unknown. Here, a novel application of a method for predicting disease occurrence that combines machine learning and statistics is used to identify the key spatial scales that define the relationship between zoonotic malaria cases and environmental change. Using data from satellite imagery, a case–control study, and a cross-sectional survey, predictive models of household-level occurrence of P. knowlesi were fitted with 16 variables summarized at 11 spatial scales simultaneously. The method identified a strong and well-defined peak of predictive influence of the proportion of cleared land within 1 km of households on P. knowlesi occurrence. Aspect (1 and 2 km), slope (0.5 km) and canopy regrowth (0.5 km) were important at small scales. By contrast, fragmentation of deforested areas influenced P. knowlesi occurrence probability most strongly at large scales (4 and 5 km). The identification of these spatial scales narrows the field of plausible mechanisms that connect land use change and P. knowlesi, allowing for the refinement of disease occurrence predictions and the design of spatially-targeted interventions.
Global habitat fragmentation is associated with the emergence of infectious diseases of wildlife origins in human populations. Despite this well-accepted narrative, the underlying mechanisms driving this association remain unclear. We introduce a nuanced hypothesis, the ‘coevolution effect’. The central concept is that the subdivision of host populations which occurs with habitat fragmentation causes localized coevolution of hosts, obligate parasites, and pathogens which act as ‘coevolutionary engines’ within each fragment, accelerating pathogen diversification, and increasing pathogen diversity across the landscape. When combined with a mechanism to exit a fragment (e.g., mosquitoes), pathogen variants will spill over into human communities. Through this combined ecoevolutionary approach we may be able to understand the fine-scale mechanisms that drive disease emergence in the Anthropocene.