Bushmeat, Health and Conservation Impacts
by Natalie Bailey, BCTF
In Africa and around the world, policy makers, NGOs and the public are increasingly focusing attention on the threat that zoonotic (cross species) disease transmission poses to human health. Global transportation of people, wildlife and livestock, combined with increasing opportunities for cross-species disease transmission has already resulted in the global emergence of diseases such as SARS, monkeypox, Ebola and HIV/AIDS. Evidence that HIV/AIDS arose from the transfer of chimpanzee-borne SIV (simian immunodeficiency virus) to humans, probably through blood-to-blood contact during the hunting and butchering of bushmeat was first published in 1999 (Gao et al. 1999). More recently, Ebola, monkeypox and SARS outbreaks have demonstrated the ease with which humans can contract and spread certain wildlife diseases, particularly those of non-human primates.
Two major factors are at play in the spread of emerging infectious diseases. First, demand for bushmeat in Africa, Asia and other parts of the world have increased the number of hunters and traders as well as both meat and live animal markets. In markets, viruses have millions of opportunities to cross over to other species and can potentially recombine into new viral strains (WCS 2003). Second, global air transportation allows for rapid movement of infected individuals (whether animal or human), which may contribute to the rapid spread of diseases. The SARS outbreak of 2003 is a vivid example of a disease that jumped across species borders into humans and was rapidly spread around the world, infecting individuals from approximately 30 countries. A monkeypox outbreak in the U.S. in 2003 demonstrated the risks of importation of live wildlife into the U.S. when prairie dogs housed with imported monkeypox-carrying African rats spread the disease to exotic pet owners.
Researchers seeking information on the origins of HIV/AIDS have demonstrated compelling evidence that bushmeat hunting and preparation may have introduced SIVcpz into human populations (Gao et al. 1999). Published in the same month that the Bushmeat Crisis Task Force was formed, this paper demonstrated that Pan troglodytes troglodytes (central chimpanzee) was the primary reservoir of HIV1 and that the species had been the source of at least three independent introductions of SIVcpz into the human population. In this and subsequent papers, authors noted that the prevalence of the bushmeat trade and the blood-to-blood contact common in hunting and preparation of bushmeat may provide opportunities for future crossover events from chimpanzees and other primates (Gao et al. 1999, Hahn et al. 2000, Wolfe et al. 2000, Daszak et al. 2000, Peeters et al. 2002, Wolfe et al.2004). At least 18 different primate SIVs have been found in at least 26 different primate species, putting humans who hunt and prepare primate bushmeat at risk for numerous genetically divergent viruses (Hahn et al. 2000, Peeters et al. 2002). Opportunities for recombination of similar retroviruses (including the newly-identified human infection of simian foamy virus, or SFV) indicate an even greater potential global health challenge (Wolfe et al.2004).
Ebola is a rapidly spreading, devastating disease that affects both human and primate populations. Hemorrhagic fevers such as Ebola can result in high mortality as they spread through dense areas. On several occasions, Ebola outbreaks have been first observed in apes, only to infect humans when infected apes are hunted or found dead in the forest, and later consumed. The 2002 Ebola outbreak in Republic of Congo and Gabon was explicitly linked to bushmeat consumption; as a result, the Government of Gabon began strictly enforcing bans on bushmeat hunting (Lawson 2002). Ebola outbreaks have occurred at least eight times in various African countries since 1994; five outbreaks involving eight different viral strains occurred in Gabon and Republic of Congo since 2001, with each human outbreak linked to the handling of a dead animal (gorilla, chimpanzee or duiker) (Leroy et al. 2004).
Ebola outbreaks are catastrophic to apes as well as to humans. Both bushmeat hunting and Ebola outbreaks have contributed to a 50% decline in ape populations in Gabon since 1983 (Walsh et al. 2003). In addition, researchers have found indicators that gorilla, chimpanzee and duiker populations may have declined by as much as 50-88% during a 2003 outbreak in the Lossi Reserve, Republic of Congo (Leroy et al. 2004). In response, veterinarians, human health agencies and conservationists are making urgent calls for control of bushmeat hunting, health education and wildlife monitoring.
Actions Addressing Global Disease Risks
More recently, the global outbreak of SARS and the emergence of monkeypox in the Midwestern region of the U.S. have raised further concerns from health professionals and conservationists regarding the demand for and global transportation of wildlife. SARS has been linked to burgeoning wildlife markets in China, where demand for masked palm civets and other species of wildlife has increased with the growing population (Bhattacharya and MacKenzie 2003). In a matter of just a few weeks, the disease had flown around the world on commercial airliners. The monkeypox case demonstrated the many ways that a disease could be transmitted, as it moved from imported African giant rats to prairie dogs to humans (CDC 2003).
Within the BCTF network, government agencies and NGOs are working together to focus on the importance of collaboration across sectors (conservation, human health professionals, wildlife veterinarians, policy makers, etc.) to encourage integrated decision-making, public awareness, fundraising and action regarding the bushmeat trade and emerging diseases. A recent meeting jointly held with the Africa Biodiversity Collaborative Group (ABCG) and the Wildlife Conservation Society (WCS) brought together representatives of each of these sectors to discuss solutions to these issues, with bushmeat as a major focus of the meeting. Further information will be posted to the BCTF website as developments continue.
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