Anthrax has been recorded for the first time in a tropical rainforest, according to researchers who say the disease is responsible for the deaths of wild chimpanzees and could pose a threat to human health.
The scientists recorded eight cases of sudden death among wild chimpanzees they were studying in the Taï National Park, Ivory Coast. All eight had been in good health shortly before their deaths, which occurred over the nine-month period from October 2001 to June 2002.
Analysis of the remains of six of the chimpanzees suggested they had all been infected and killed by the bacterium that causes anthrax.
Writing in Nature today, Fabian Leendertz and his colleagues speculate about the source of the infection.
They say it is unlikely the chimpanzees got anthrax from eating an infected animal. The anthrax bacterium usually infects herbivores such as antelope and, in the 16 years that they have been studied, the Taï National Park chimpanzees have only ever been known to eat monkey meat.
Drinking contaminated water, say the scientists, could have caused the infection. But a search for dead animals of other species that would have shared the chimpanzees' water was fruitless. However, the researchers have not ruled out this explanation, as water sources in the forest are numerous and animal carcasses are hard to find. They warn that if contaminated water is to blame, the long-term effects could be worse than if the infection stemmed from a single infected animal.
The findings mean that anthrax joins the Ebola virus and other pathogens that threaten both the survival of endangered primates in Africa and, because of the potential for the pathogens to move between primate species, human health.
Leendertz and his team say that the hunting and consumption of bushmeat raises the likelihood that humans will be exposed to a range of deadly pathogens and say the practices should be discouraged.
Reference: Nature 430, 451 (2004)