It is speculated that leprosy develops after a long latency period following M. leprae infection in infancy. While the actual duration of this latency period has never been proven in human patients, Dr. Suzuki and his colleagues were recently able to demonstrate a long incubation period of leprosy in a female chimpanzee.
Haruna was brought from Sierra Leone to Japan in 1980 around age two. She was used in medical research for 10 years before being retired to a chimpanzee sanctuary. In January 2009, at the age of 31, she was found to have swellings and nodules on her face. Further tests resulted in a diagnosis of lepromatous leprosy. Haruna was put on multidrug therapy (administered with bananas or vegetable juice) and made a complete recovery.
Based on genetic analysis of M. leprae in Haruna's case, Dr. Suzuki and his colleagues scientifically demonstrated for the first time a long incubation period of leprosy. The genotype of Haruna's M. leprae, which has been identified only in West Africa, indicated she was infected during infancy and developed leprosy in Japan some 30 years later. Even in retirement, Haruna made an important contribution to medical research.