Human viruses spread by coughing and sneezing tourists are the latest threat to Africa's endangered gorillas and chimpanzees, according to German researchers. ( dpa )
While eco-tourism is considered a way of combatting poaching, the researchers' report, published in the journal Current Biology, says the influx of human tourists from all over the world is putting the apes at risk of respiratory diseases for which they have no natural immunity.
Just as native Americans were decimated by measles, smallpox and other epidemics brought across the Atlantic by European colonists, gorillas and chimps in Africa are now succumbing to viral strains traced as far away as Asia and Argentina - meaning human carriers are to blame.
The new study by researchers of the Robert Koch Institute in Berlin, the Max Planck Institute for Evolutionary Anthropology in Leipzig and the Centre Suisse des Recherches Scientifiques in the Ivory Coast, confirms 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 - so far. But the situation could get out of hand unless strict hygienic measures are taken now.
"We need to be much more proactive about instituting strict hygiene precautions at all ape tourism and research sites," senior author Fabian Leendertz, a wildlife epidemiologist at the Robert Koch Institute in Berlin, said in a release.
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 Tai National Park in Cote 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.
Ironically, the mere presence of tourists and research scientists has served as a deterrent to illegal hunting and poaching of apes. Thus the benign humans, while importing potentially deadly viruses, have nonetheless helped the apes to prosper and multiply.
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 Tai.
"However, it comes with some hygienic problems which need to be addressed."