A French study found that some 85% of questionnaire respondents in Cameroon had eaten primate meat, with the exposure risk to zoonotic disease in any given village directly related to the relative density of non-human primates and their proximity to human settlements.
Animal diseases that infect humans are a major threat to human health, and diseases often spill-over to humans from non-human primates. Now, researchers have carried out an extensive social sciences evaluation of how populations in Cameroon interact with non-human primates, pointing toward behaviours that could put people at risk of infection with new diseases.
Zoonotic diseases – those which originate in other animal species before spilling over to humans – now constitute more than 60% of emerging infectious diseases. Of these zoonotic diseases, 70% reportedly come from wild animals. Because of the similarity between humans and nonhuman primates, these monkeys and apes serve as frequent reservoirs or amplifiers for pathogens that pose a risk to human populations.
In the new work, Tamara Giles-Vernick of the Institut Pasteur, France, and Victor Narat of the French Centre for National Scientific Research, with their colleagues carried out surveys, real-time data collection, oral history interviews, and wild meat surveys to paint a full picture of the physical exposure of people in south-eastern Cameroon to non-human primate species. Data were collected in 2016 and 2017 and included information from multiple villages and hundreds of people.
The researchers found that Cameroonian adults have frequent physical contact with primates, and more with monkeys than apes. This contact is most often through hunting, butchering, preparing and consuming meat, but also includes injuries sustained from gorillas. Some 85% of questionnaire respondents had eaten primate meat in their lifetimes. In general, the exposure risk in any given village was directly related to the relative density of non-human primates and their proximity to human settlements.
“National and international authorities should support improved surveillance of humans and abundant monkey species, as well as popular messages to promote safe meat handling practices,” the researchers say. “Multidisciplinary social science and ecological approaches should be used to improve surveillance and communications with forest populations about neglected tropical diseases.”
Emerging infectious diseases of zoonotic origin constitute a recurrent threat to global health. Nonhuman primates (NHPs) occupy an important place in zoonotic spillovers (pathogenic transmissions from animals to humans), serving as reservoirs or amplifiers of multiple neglected tropical diseases, including viral hemorrhagic fevers and arboviruses, parasites and bacteria, as well as retroviruses (simian foamy virus, PTLV) that are pathogenic in human beings. Hunting and butchering studies in Africa characterize at-risk human social groups, but overlook critical factors of contact heterogeneity and frequency, NHP species differences, and meat processing practices. In southeastern Cameroon, a region with a history of zoonotic emergence and high risk of future spillovers, we conducted a novel mixed-method field study of human physical exposure to multiple NHP species, incorporating participant-based and ecological methodologies, and qualitative interviews (n = 25). We find frequent physical contact across adult human populations, greater physical contact with monkeys than apes, especially for meat handling practices, and positive correlation of human exposure with NHP species abundance and proximity to human settlement. These fine-grained results encourage reconsideration of the likely dynamics of human-NHP contact in past and future NTD emergence events. Multidisciplinary social science and ecological approaches should be mobilized to generate more effective human and animal surveillance and risk communications around neglected tropical diseases. At a moment when the WHO has included “Disease X”, a presumably zoonotic pathogen with pandemic potential, on its list of blueprint priority diseases as, new field-based tools for investigating zoonotic disease emergence, both known and unknown, are of critical importance.
Victor Narat, Mamadou Kampo, Thibaut Heyer, Stephanie Rupp, Philippe Ambata, Richard Njouom, Tamara Giles-Vernick