Human-Borne Pathogens: Are They Threatening Wild Great Ape Populations?

Abstract

Climate change and anthropic activities are the two main factors explaining wild great ape habitat reduction and population decline. The extent to which human-borne infectious diseases are contributing to this trend is still poorly understood. This is due to insufficient or fragmented knowledge on the abundance and distribution of current wild great ape populations, the difficulty obtaining optimal biological samples for diagnostic testing, and the scarcity of pathogen typing data of sufficient quality. This review summarises current information on the most clinically relevant pathogens of viral, bacterial, parasitic, and fungal nature for which transmission from humans to wild great apes is suspected. After appraising the robustness of available epidemiological and/or molecular typing evidence, we attempt to categorise each pathogen according to its likelihood of truly being of human origin. We further discuss those agents for which anthroponotic transmission is more likely. These include two viral (Human Metapneumovirus and Respiratory Syncytial Virus), one bacterial (diarrhoeagenic Escherichia coli), and two parasitic (Cryptosporidium spp. and Giardia duodenalis) pathogens. Finally, we identify the main drawbacks impairing research on anthroponotic pathogen transmission in wild great apes and propose research lines that may contribute to bridging current knowledge gaps.

Common cold viruses circulating in children threaten wild chimpanzees through asymptomatic adult carriers

“…Although a MPXV outbreak in chimpanzees in Côte d’Ivoire in 2017 likely had sylvatic origins 21 , this is the exception to the rule. In general, the risk of reverse zoonotic transmission from humans appears to be greater than the risk from other animals 39 , 40 . Common cold viruses have no known reservoirs except for humans 41 – 43 .…”

Anthropogenic Pressures on Gorillas: A Case of Grauer’s Gorillas in Maiko National Park, the Democratic Republic of Congo

“…The number of clinically relevant pathogens that affect wild great apes may also affect humans and vice versa [101]. At the same time, the threat of disease transmission between wildlife, domestic animals, nature, and people is predicted to increase following a continuing growth of the human population and subsequent land-use change, deforestation, hunting, bushmeat trade, and increased field research on apes among other driving opportunities for disease pullover [102,103].…”

“…Epidemics pose a potentially devastating threat to Grauer's gorillas. They are affected by many parasites and diseases, including Ebola, common cold virus, pneumonia, smallpox, chickenpox, tuberculosis, measles, rubella, and yellow fever [102]. This is not surprising, considering that respiratory infections are the primary cause of morbidity and mortality in gorillas in most settings [102,113].…”

“…They are affected by many parasites and diseases, including Ebola, common cold virus, pneumonia, smallpox, chickenpox, tuberculosis, measles, rubella, and yellow fever [102]. This is not surprising, considering that respiratory infections are the primary cause of morbidity and mortality in gorillas in most settings [102,113]. Of note, viruses that are relatively benign in human can cause lethal outbreaks in ape populations, indicating poor host adaptation and a lack of resistance in apes [102].…”

Epidemiology of Wildlife Infectious Diseases

“…A novel point of view on transmitting infectious diseases is presented by Koster et al [ 1 ] in a review of how human pathogens affect great apes. This perspective is reinforced by Paungpin et al [ 2 ], who discovered human influenza viruses in macaques in Thailand.…”