Abstract
Infectious disease has recently joined poaching and habitat loss as a major threat to African apes. Both “naturally” occurring pathogens, such as Ebola and Simian Immunodeficiency Virus (SIV), and respiratory pathogens transmitted from humans, have been confirmed as important sources of mortality in wild gorillas and chimpanzees. While awareness of the threat has increased, interventions such as vaccination and treatment remain controversial. Here we explore both the risk of disease to African apes, and the status of potential responses. Through synthesis of published data, we summarize prior disease impact on African apes. We then use a simple demographic model to illustrate the resilience of a well-known gorilla population to disease, modeled on prior documented outbreaks. We found that the predicted recovery time for this specific gorilla population from a single outbreak ranged from 5 years for a low mortality (4%) respiratory outbreak, to 131 years for an Ebola outbreak that killed 96% of the population. This shows that mortality rates comparable to those recently reported for disease outbreaks in wild populations are not sustainable. This is particularly troubling given the rising pathogen risk created by increasing habituation of wild apes for tourism, and the growth of human populations surrounding protected areas. We assess potential future disease spillover risk in terms of vaccination rates amongst humans that may come into contact with wild apes, and the availability of vaccines against potentially threatening diseases. We discuss and evaluate non-interventionist responses such as limiting tourist access to apes, community health programs, and safety, logistic, and cost issues that constrain the potential of vaccination.
Highlights
Poaching and habitat loss are known major threats to African apes [1], but what has only in the last few years come into focus is that infectious disease is a threat of similar magnitude
To assess future potential spillover disease risk, we examined human vaccination rates and reported cases for five exemplar great ape range countries using the UNICEF/World Health Organization (WHO) 2009 global immunization summary [30] and the WHO 2009 WHS (World Health Statistics) [31], for seven diseases known to be communicable to great apes (Table 2)
Infectious disease is a serious a threat to African apes, along with poaching and habitat loss. This threat is likely to increase as human disease spillover into wild ape populations intensifies, both because of rising population pressure around protected areas and because of increasing ape tourism
Summary
Poaching and habitat loss are known major threats to African apes [1], but what has only in the last few years come into focus is that infectious disease is a threat of similar magnitude. Wild populations of gorillas and chimpanzees are threatened by a diverse array of virulent pathogens, including Ebola virus [1,2], Anthrax [3], simian immunodeficieny virus (SIV) [4], and a variety of human respiratory viruses [5,6]. These recent illustrations of the magnitude of disease threat have intensified a longstanding debate about the advisability of medical interventions such as vaccination. Our objective is to provide a scientifically based discussion about the need for, feasibility and cost effectiveness of intervention for disease threats in African apes
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