Human researchers are killing wild chimpanzees by inadvertently giving them colds, a new study shows for the first time.
The researchers in Africa now face a dilemma: let tourists and scientists get close to Africa鈥檚 great apes and risk spreading diseases, or curb contact with the apes and leave them vulnerable to a bigger threat 鈥� poachers.
For scientists to study wild gorillas and chimpanzees, and for eco-tourists to see them, groups of 鈥渉abituated鈥� apes must let people get within a few metres of them. It has long been suspected that this spreads human respiratory viruses, which apes can catch. Up to half the apes in such groups have died after showing respiratory symptoms.
Advertisement
However, it is hard to pinpoint what has killed a wild ape, says Fabian Leendertz of the in Berlin, Germany, who runs a chimp health project in the Tai forest in Ivory Coast.
Researchers have found human gut bugs such as Escherichia coli in ape droppings 鈥� not surprising, as these bacteria persist in the environment, where eco-tourists with diarrhoea deposit them.
Double whammy
But to catch a human respiratory virus you have to be close to someone coughing. Habituated Tai forest chimps had five separate outbreaks of respiratory disease between 1999 and 2005. Nearly all had cold symptoms, and between 3 and 19% died, mainly juveniles.
Leendertz and his colleagues found either human respiratory syncytial virus, or human metapneumovirus in victims, as well as pathogenic bacteria such as Streptococcus. The viruses commonly cause cold symptoms in human adults, but can be serious in children.
鈥淔rom the virus alone the chimps would have probably not have died,鈥� Leendertz says. But the bacterial infections that accompanied them were deadly. When zoo chimps get these viruses, they also get antibiotics to kill bacteria.
Should sneezing apes in habituated groups also get antibiotics? 鈥淲e must decide how much we have to invasively treat the wild apes,鈥� says Leendertz. 鈥淒o we have to get away from the 鈥渉ands off鈥� philosophy?鈥�
Protective effect
The answer is probably not to end close encounters between apes and humans, which pay local people to protect the animals from poachers. 鈥淚n the Tai forest we have the highest density (of chimps) around the research and tourist sites,鈥� Leendertz says. 鈥淲ithout research our site would probably have [no chimps] left.鈥�
Researchers walking across Tai National Park found their likelihood of running into signs of chimpanzees declined the farther they got from the research project or from a tourist site 鈥� but their likelihood of encountering signs of poaching increased.
鈥淭his is the first time people have quantified and compared the disease effects of research and tourism with the anti-poaching effect,鈥� says study co-author Peter Walsh of the .
The researchers now wear heavy N95 hospital face masks in the field. 鈥淭hey鈥檙e a bit hot, but OK,鈥� says Leendertz. 鈥淲e need to find ways to maximise the benefit of research and tourism by minimising the negative effect of disease.鈥�
For the apes, the choice now is between the poacher and the plague.
Journal reference: (DOI: 10.1016/j.cub.2008.01.012)
