A mysterious disease that was once common in humans appears to have crossed the species barrier and been transferred to one of our closest primate relatives. Researchers reported Wednesday that leprosy was discovered in two groups of West African chimpanzees. This is the first time it has been documented in wild chimps. Although the cause of the outbreaks remains unknown, it is believed that the disease is still rare among the chimp population.
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Mycobacterium Leprae is a cousin to tuberculosis bacteria and causes leprosy. Leprosy bacteria is similar to viruses but unlike other bacteria, it can invade our cells and hijack their functions to reproduce. Because of its unique nature, symptoms after infection can take up to two decades to manifest. Initial symptoms include sores or lesions that appear pale. The chronic infection can eventually lead to the destruction of nerve and eye cells, which can cause symptoms such as loss of sensation, paralysis and blindness.
History with leprosy (also known as Hansens disease) dates back to Biblical times. Leprosy, despite its scary reputation, is a relatively common condition. It is difficult to transmit the disease, which usually requires close contact for months. 95% of people are naturally immune. Although the bacteria has developed resistance to some of the older drugs that were used to treat the disease in the 1940s it can still be treated with long-term antibiotic therapy.
Leprosy has become a rare disease due to improvements in sanitation and availability of antibiotics. There are still areas of the world where these resources don't exist, with around 200,000 leprosy cases reported in 2019. Researchers discovered that bacteria can also be carried by humans in some areas of the world. This was likely due to the fact that the bacteria was introduced into the Americas by European colonizers. Leper armadillos can sometimes infect humans, which is a karmic twist.
Studies have shown that chimpanzees in captivity can also get leprosy. Researchers studying wild chimps from West Africa discovered strange leprosy-like symptoms on a male chimp named Woodstock in June 2018. They wondered if similar symptoms had been seen in others from the same area or other communities.
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Tissue samples taken from the chimp's body after their death revealed that Zora, a chimp, had traces of leprosy bacteria in her blood before she was killed by a leopard attack in 2009. Zora's skin defects were confirmed by subsequent examinations of her photos. However, Zora's stored fecal samples indicated that the infection had been present at least seven years before Zora died. The group was able to confirm that there were other cases of leprosy among two distant chimpanzee communities in Guinea-Bissau and Cte dIvoire.
Kimberley Hockings (a researcher at the Center for Ecology and Conservation at University of Exeter in the UK) said that this is the first confirmed case of leprosy in non-human animals in Africa. It is amazing that this happens to be in our closest living relative the chimpanzee. This is especially remarkable considering how well-studied chimpanzees in the wild.
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Nature published the team's findings Wednesday.
Researchers aren't sure if humans are the primary suspect in these cases. The genetic strains found in each chimp group were distinct from each other, and they are rarely found in humans or any other animal reservoirs. The transmission of leprosy is made more difficult by the fact that neither chimp community spends much time with humans. It is possible that leprosy may have been spreading to nonhuman species and the chimps could have caught it from them. Scientists in the UK discovered evidence that leprosy can also be caught by squirrels in 2016.
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The good news is that leprosy in chimpanzees appears to be very rare. The researchers found only four cases of chimp leprosy among the 467 chimpanzees they observed in Woodstock's community and in other nearby communities. Wild chimpanzees don't have the same access to antibiotics as humans. Researchers fear that leprosy could be endemic in these wild chimps. Researchers say that more research is required to determine the spread and origins leprosy in wild chimpanzee populations.
Hockings stated that Western Chimpanzees are in grave danger. Even a small number of them could be endangered.
