For several decades, ZSL has been at the forefront of a broad body of work investigating disease in wild animal populations and the conditions under which they might be transmitted to other species, including human beings (1). ZSL also has considerable experience in policy and regulatory approaches to wildlife health and to wildlife trade (2). With experts in wildlife veterinary care and disease investigation, wildlife epidemiology, disease risk analysis and surveillance, bushmeat research, and wildlife trade and policy, ZSL believes it is uniquely placed to offer a balanced, informed and evidence-based opinion on the risks associated with the spread of zoonotic disease and appropriate mitigation measures.
This position statement was developed by a ZSL cross-institutional working group.
The global pandemic caused by COVID-19 has brought concerns of wildlife health and impacts on human health to the fore of public attention worldwide and sparked calls for immediate action, including bans on wildlife trade. A previously unknown coronavirus, SARS-CoV-2, is the cause of a new disease known as COVID-19, which currently (May 2020) is causing a pandemic. COVID-19 has wrought tremendous human suffering, economic devastation, and social consequences. While genomic data strongly support the conclusion that the virus has a zoonotic origin, most likely from a species of bat (3), an undetermined wild or domestic host could have played an intermediary role in transferring SARS-CoV-2 to people (4). Although concerns about zoonotic spill-over are not new (5), the COVID-19 pandemic has raised awareness among the public and decision-makers of the risk of novel disease transmission from wildlife, and most acutely of the links between wildlife exploitation, trade, and zoonotic disease transfer (6), particularly in so-called “wet markets” (7). This has led to calls for outright bans on wildlife trade, especially where these exist to supply human consumption, and for closing wet markets.
While calls for bans or market closures are well intentioned, their impacts are likely to be short term, limited, and potentially damaging as they move trade into illegal markets where capacity to enforce regulations is extremely challenging. Highly targeted bans or market closures (8) can have their place as measures to mitigate known risks of zoonotic disease emergence or as short-term measures for minimizing disease spread. However, they are unlikely to present long-term viable solutions to what is a highly complex problem. In practice, bans can be challenging to implement and enforce. In many cases, legal frameworks are already in place to regulate trade, but insufficient enforcement is often the greatest barrier to effective implementation. Therefore, imposing additional bans without due support to enforcement and compensatory mechanisms would likely drive activities underground, making regulation even more difficult and potentially further accelerating exploitation (9). Millions of people in developing countries currently rely on wild meat to meet their nutritional needs (10). Consequently, sudden actions that restrict or hinder access to these markets risk impacting food security, human well-being and livelihoods, particularly for already vulnerable groups and societies. Further consideration of market bans must take a context specific and evidence-based approach to understanding the consequences of bans, both on food security needs of local communities and potential unintended negative consequences.
ZSL believes that the unsustainable exploitation of wildlife either for consumption or other uses must stop, that animal welfare standards must improve, and that known high-risk species for zoonotic disease emergence should be closely regulated and ultimately should not be traded for food. The solutions to reducing future risks from zoonotic disease emergence need to be holistic and multi-faceted. Wildlife exploitation and trade undoubtedly needs vastly better enforcement and regulation, particularly in a post-COVID-19 world. Specifically, we need to improve enforcement of existing wildlife conservation, animal welfare and public health regulations, where these exist, and bring in new regulations where they do not. Measures such as increasing biosafety standards and ensuring facilities and staff meet acceptable levels of sanitation and hygiene, are likely to hold greater longer-term promise than outright forced closures. While policies exist to detect and prevent the importation of infected hosts of domestic animal diseases, far less has been done to regulate diseases related to wildlife; there is an urgent need to introduce the same degree of sanitary regulations for the movement of wild animals as apply to those for domesticated species. These measures should include risk assessments of zoonotic disease emergence, with trade being particularly regulated for high-risk species in taxa such as rodents, bats and primates (11). Finally, we need significant investment in research to understand the risk factors for zoonotic emergence from wildlife and to identify effective measures for disease prevention.
Coming out of this pandemic, we must reset our relationship with nature. Rampant biodiversity loss increases the chances of future zoonotic spillovers and facing more frequent pandemics. Actions to control wildlife markets are not enough. ZSL strongly believes that the root causes of the COVID-19 pandemic must be addressed. That this has occurred at the same time the planet is undergoing a biodiversity extinction crisis (12) is not a coincidence. Biodiversity conservation and safeguarding public health are inextricably linked through a range of complex ecological, political and socio-economic pathways. Many drivers of biodiversity loss, such as habitat loss and encroachment and unsustainable exploitation, are also drivers of zoonotic disease emergence. As a result, the risk of zoonotic disease emergence increases as biodiversity is lost (13). This pandemic is another reminder of how critical it is that we identify sustainable development pathways that enable wildlife to thrive and ecosystems to recover.
COVID-19 underlines that we ALL need to work together to conserve nature and preserve the ecosystem services, including disease regulation, that biodiversity provides while also understanding and changing human behaviours and activities which lead to disease emergence. COVID-19 has shown again that zoonotic disease is one of the greatest challenges to public health and wellbeing. ZSL remains committed to working with partners to further our understanding of pathways for zoonotic disease transmission and to supporting governments, civil society and other actors to take and implement effective, equitable and evidence-based actions to reduce the risk of future disease emergence and safeguard species, habitats and livelihoods.
References and Supplementary Information
1. This position paper has an effective term date of 1 year from the date of issue. As such, the facts and figures contained herein may become outdated. It should not be treated or read as a definitive source of information on the topic, but rather as an evidence-based explanation for ZSL’s position on various debates and discussion points that have ensued in the wake of COVID-19. Note ZSL uses an inclusive definition of the term wildlife that means wild fauna and flora, in keeping with the way the term is used by the United Nations.
2. Daszak, P. et al. 2000. Science 287: 443-449; Jones, K. et al. 2008. Nature 451: 990-993; Kümpel, N.F. et al. 2015. Ebola and bushmeat: myth and reality. FAO, Rome.; Cunningham, A. et al. 2017. Phil. Trans. R. Soc. B 372: 20160167. doi: 10.1098/rstb.2016.0167
3. E.g.: Bennett, E.L. et al. 2008. Cons. Biol. 21: 884-887; East, T. et al. 2005. Biol. Conserv. 126: 206-215; Kamins, A.O. et al. 2011. Biol. Conserv. 144: 3000-3008; Musing, L. et al. 2018. Implementation of the CITES Appendix II listing of European Eel Anguilla anguilla. ZSL and TRAFFIC. AC30 Doc. 18.1 A1.
4. A study produced by ZSL in 2013 identified 137 bat viruses of which 61 were known to be capable of infecting humans at the time (Luis, A.D. et al. 2013. Proc. Biol. Sci. 280: 20122753. doi:10.1098/rspb.2012.2753). Bats harbour a greater diversity of coronaviruses than any other mammalian host (Drexler et al. 2014. Antiviral Res. 101: 45-56. doi:10.1016/j.antiviral.2013.10.013.) and bat-borne coronaviruses have caused several emerging infectious disease outbreaks of global significance, including SARS. Genetic data obtained so far indicate that SARS-CoV-2 bears close similarity to a group of SARS-CoV-like coronaviruses that had previously been found in bats in China (Wu, F. et al. 2020. Nature 579: 265-269. doi:10.1038/s41586-020-2008-3; Hu et al. 2018 Emerg. Microbes Infect. 7: 1–10 doi:10.1038/s41426-018-0155-5). Thus, while not proved, available evidence indicates a bat source for SARS-CoV-2. While direct bat to human transmission cannot be entirely ruled out, the zoonotic emergence of several previous coronaviruses, including SARS and MERS, has involved an intermediate host (civets and camels, respectively).
5. It is not yet known if an intermediate host transferred SARS-CoV-2 from bats to people. Early reports suggested pangolins as the intermediate host, but the virological evidence to date does not support this (Andersen, K.G. et al. 2020. Nature Medicine 26: 450-452. doi: 10.1038/s41591-020-0820-9). A range of potential intermediate host candidates (mostly mammals) has been identified (Qiu, Y. et al. 2020. Microbes and Infection doi:10.1016/j.micinf. 2020.03.003).
6. Zoonotic disease emergences originate from both wild and domesticated animals that act as hosts and vectors of pathogens, with evidence that, among wild mammals at least, primates and bats (Johnson, C.K. et al. 2020. Proc. R. Soc. B 287: 20192736. doi:10.1098/rspb.2019.2736), and possibly rodents (Luis et al. 2013 Proc. R. Soc. B. 280: 20122753. dx.doi.org/10.1098/rspb.2012.2753) host more zoonotic viruses than other species, though clearly not all are high risk. Historically, human exposure to such disease risks has been limited, but zoonotic disease emergence and spread are being exacerbated by human behaviours and activities, including habitat destruction due to agricultural encroachment and logging, over-exploitation of wildlife, and the increased connectedness of a growing human population. For example, the emergence of Nipah virus in Malaysia in 1998 was causally linked to intensification of pig production at the edge of tropical forests where fruit bats live. While emerging zoonotic infectious diseases arise through our contact with wildlife, the natural world they are a part of is fundamental for human health and wellbeing (Diaz, S. et al. 2019. IPBES Summary for policymakers of the global assessment report on biodiversity and ecosystem services).
7. The links between the wildlife trade and human disease are well established, albeit imperfectly understood. One of the primary mechanisms by which human populations come into contact with wildlife-borne disease is through wildlife utilisation and trade (Pavlin, B.I. et al. 2009. Emerging Infectious Diseases 15: 1721-1726. Doi: 10.3201/eid1511.090467). While illegal wildlife harvest and trade is most often invoked, legal activities (including low-level subsistence trade and trade from farmed or cultivated sources) can also involve considerable disease transmission risks. Wildlife trade increases the risk of transmission for several reasons. For example, in addition to bringing people into direct contact with tissues, excreta and body fluids of dead wildlife, it can involve the physical transport of species (dead or alive), and the novel pathogens they carry, outside of their native range to new environments (Carreira, J.C.A. et al. 2020. Open Journal of Animal Sciences 10: 64-133. Doi: 10.4236/ojas.2020.101006). It can bring species which ordinarily would not co-exist together, in some cases alive and in confined environments. Stressful conditions, such as capture from the wild, enhance the excretion of pathogens from wild animals and increase their vulnerability to infection by novel pathogens, creating the ideal circumstances for cross-species disease transmission to occur. Live trade likely represents the greatest risk of transmission, but risks remain even with carcases or wildlife parts. However, we still have much to understand about zoonotic disease emergence and transmission pathways.
8. A wet market is a non-specific term for a market that sells fresh (not necessarily live), perishable produce, including fruit and vegetables, but also meat and fish. Not all wet markets are wildlife markets, and not all wet markets that sell wildlife are necessarily disease risks. The term has come to be interchangeably used for wildlife markets, and more specifically wildlife markets selling live animals.
9. An open seafood market in Wuhan that trades in domestic and wild animals (but apparently not bats), and which had been implicated as the original source of the virus, was closed on 01 January 2020 and disinfected, but at the time of writing the market had been reopened.
10. Garner, T.W.J. et al. 2009. EcoHealth 6: 148-151. Doi: 10.1007/s10393-009-0233-1; Bonwitt, J. et al. 2018. Social Science and Medicine 200: 166-173. Doi: 10.1016/j.socscimed.2017.12.028; Cronin et al. 2015. PLoS One 10: e0134464. Doi: 10.1371/journal.pone.0134464
11. Rushton, J. et al. 2005. How important is bushmeat consumption in South America: now and in the future? ODI Wildlife Policy Briefing Number 11; Nasi, R. et al. 2011. International Forestry Review 13: 355-368. Doi: 10.1505/146554811798293872
12. These taxonomic groups are considered relatively high risk for zoonotic disease transmission compared with other mammalian taxa and are also subject to high rates of hunting. However, there is also evidence that the presence of potential viral zoonoses are homogenous among mammalian taxonomic orders; therefore, identifying high-risk viruses on the assumption that some taxonomic orders of hosts are disproportionate sources of zoonoses risks might risk inadvertently missing important sources of zoonotic emergence in the future (Mollentze & Streicker 2020 PNAS Doi.org/10.1073/pnas.1919176117). That rodents, bats and primates appear to present a higher zoonotic disease risk might involve factors other than the distribution of zoonotic pathogens amongst wildlife and highlights the need for further research in this area.
13. Diaz, S. et al. ibid.
14. Civitello et al. 2015. Proc. Natl. Acad. Sci. USA. 112: 8667-8671. Doi: 10.1073/pnas.1506279112; Olivero, J. et al. 2017. Scientific Reports 7: 14291. Doi: 10.1038/s41598-017-14727-9
Date: 4th May 2020
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