Shortly after the end of World War II, the first cases of a mysterious skin affliction began to affect taro farmers on the Micronesian island of Satowan. In 2006, after a man from Satowan with a skin infection was diagnosed with Mycobacterium marinum at a clinic in Portland, Oregon, government health authorities in Micronesia invited a team of researchers led by Joseph V. Lillis, M.D., of the Oregon Health and Sciences University, to investigate. After evaluation by team members, 39 patients with the disfiguring skin infection were treated with the antibiotic doxycycline for 3 months.
Followup evaluation of a few patients showed dramatic improvement among those with limited disease. The Satowan islanders affected by the skin disease had suffered from symptoms for an average of 13 years. Its principal symptoms were chronic, progressive, large, warty plaques primarily affecting the upper and lower limbs. By 2004, the infection had affected more than 10 percent of the island's population of 650. Up until this point, surgical and other treatments had proved ineffective and there had never been a formal investigation of the condition.
The team's investigation showed that the principal risk factor for the disease was swimming or bathing in the stagnant waters of craters left by Allied bombing in World War II. The craters were filled with large numbers of medaka fish that were originally introduced to the island during World War II by the Japanese to decrease the mosquito population. The medaka fish is known to tolerate chronic infection with M. marinum. This bacterium rarely affects humans except through aquatic exposure of a cut or sore. The second major risk factor for the infection was engaging in taro farming, which requires standing or walking around in water-filled fields. All of those infected were taro farmers and most (95 percent) reported a history of a cut or abrasion near the site of their skin infection.
The investigators were unable to definitively identify M. marinum in the 19 tissue samples collected from Satowan patients, possibly because of storage at suboptimal temperatures and a 5-day interval between collection of the tissue and plating the culture.
Further microbiological assessment is needed to definitively identify the mycobacterial organism causing this skin disease. With intervention and therapy, the researchers believe that mitigation of this significant public health problem on Satowan is possible. The study was supported by the Agency for Healthcare Research and Quality (HS17552).
See "Sequelae of World War II: An outbreak of chronic cutaneous nontuberculous mycobacterial infection among Satowanese islanders," by Dr. Lillis, Vernon E. Ansdell, M.D., Kino Ruben, M.D., and others, in Clinical Infectious Diseases 48, pp. 1541-1546, 2009.
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