Chimpanzees Used for Medical Research Shed Light on the Pathoetiology of Leprosy

Koichi Suzuki; Kazunari Tanigawa; Akira Kawashima; Tatsuo Miyamura; Norihisa Ishii


Future Microbiol. 2011;6(10):1151-1157. 

In This Article

Routes of M. leprae Infection in Chimpanzees

There is a possibility that M. leprae might be transmitted among chimpanzees in Africa.[30] Another possibility is that contact with a human patient with M. leprae occurred during the 2–3 month period the chimpanzees were housed in outdoor cages while awaiting shipment after capture.[27] In addition, possible transmission from the environment cannot be excluded. There have been some reports of African wild chimpanzees with nasal discharge thought to be caused by infectious diseases, including leprosy.[12] However, it is difficult to make a diagnosis of leprosy by just observing and without performing a close examination of wild animals. If peripheral neuritis or ulcerations of extremities exist, survival in the wild must be quite difficult.

M. leprae infection is thought to occur when a subject is exposed to a certain number of bacilli either directly or indirectly.[12,13] Although the disease develops after a long incubation period, this progression of disease has never been proven since it is not possible to identify the infection period in human subjects. The life expectancy of chimpanzees is 40–50 years, and the four chimpanzees with leprosy in the present report are considered to be elderly. Although it is not clear what triggered the initiation of active growth of M. leprae after the long incubation period, it was speculated in that Haruna's case a recent change in her social group might have resulted in stress that may have transiently impaired her immune system.[35]


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