Great Apes endangered by human viruses

The opening of gorillas and chimpanzees reserves for tourism is often portrayed as the key to conserving these endangered great apes. There are also however serious concerns that tourism may expose wild apes to infection by virulent human diseases

January 25, 2008

A new study published in the journal Current Biology by researchers of the Robert Koch Institute (Berlin), the Max Planck Institute for Evolutionary Anthropology (Leipzig) and the Centre Suisse des Recherches Scientifiques (Ivory Coast) confirms the disease threat, finding the first direct evidence of virus transmission from humans to wild apes. The study also showed however that research and tourism projects strongly suppressed the poaching of chimpanzees. This protective effect outweighed the substantial chimpanzee mortality caused by human disease introduction.

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Respiratory disease introduction by humans has long been suspected at sites where apes in the wild have been in close contact to humans but this is the first study to diagnose the disease agent and quantify the population impact. "We need to be much more proactive about instituting strict hygiene precautions at all ape tourism and research sites", says Fabian Leendertz, senior author of the paper and a wildlife disease epidemiologist at the Robert Koch Institute in Berlin. "One possibility for promoting compliance is a certification process similar to the green labelling system now used in the timber industry."

The study used a multidisciplinary approach involving behavioural ecology, veterinary medicine, virology and population biology to track human disease introduction into two chimpanzee communities at Taï National Park in Côte d’Ivoire, where researchers first began to habituate chimpanzees to human presence in 1982. Tissue samples taken from chimpanzees that had died in a series of outbreaks dating back to 1999 tested positive for two human respiratory viruses that are major sources of human infant mortality in the developing world, namely human respiratory syncytial virus and human metapneumovirus. Viral strains sampled from the chimpanzees were closely related to pandemic strains concurrently circulating in human populations as far away as China and Argentina, suggesting recent introduction from humans into the chimpanzees. The authors also used clinical observations and demographic analyses to infer that similar respiratory outbreaks could date as far back as 1986.

The research project has however also had strongly positive effects. Longitudinal surveys showed that the presence of researchers had suppressed poaching activities in the surrounding area. Consequently, chimpanzee densities at both the research study site and a nearby chimpanzee tourism site were much higher than would be expected given their accessibility to poachers. "Researcher presence is confirmed to have a major positive impact on the protection of an area," says co-author Christophe Boesch of the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Leipzig, who directs the research project at Taï. "However, it comes with some hygienic problems which need to be addressed".

"The study confirms that multidisciplinary research is needed to investigate different issues involved in ape conservation", said Paul N’Goran, a researcher at the Centre Suisse de Recherches Scientifiques en Côte d’Ivoire. "Our study shows the critical role that scientific research can play in monitoring the impact and effectiveness of conservation strategies".