Consequences of Non-Intervention for Infectious Disease in African Great Apes

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.

Vaccinating captive chimpanzees to save wild chimpanzees

“…The ability to accurately diagnose diseases that afflict wild apes has opened the door to an active management response: vaccination (10). The door has been pushed further open by recent advances in vaccinology, including experimental vaccines against several previously unpreventable disease threats to wild apes, new vaccine platforms that reduce or eliminate the risk of infection or vaccine spillover into nontarget species, and new adjuvants that enhance vaccine efficacy (11).…”

Baboons as potential reservoirs of zoonotic gastrointestinal parasite infections at Yankari National Park, Nigeria

“…There is no doubt that anthropogenic changes which increase contact between humans and wildlife will inevitably play a role in the emergence and re-emergence of zoonotic diseases 11,14 . Parasitic disease control programmes should emphasis; limited contact with non-human primates, and vaccination against potentially threatening diseases 14 .…”

Regional Action Plan for the Conservation of Western Lowland Gorillas and Central Chimpanzees 2015–2025

“…Given the low birth rates of great apes, recovery of a population from diseaserelated mortality can be slow. Ryan and Walsh (2011) predicted that recovery from a single outbreak would range from five years for a low mortality event (e.g., 4% loss in a respiratory outbreak),…”