A large number of leptospirosis cases on Yaeyama Islands, July - September 1999 - Okinawa
(IASR 2000; 21: 165-166)

Leptospirosis, whose primary reservoirs are rodents, is a rare zoonosis in Japan. However, in Okinawa Prefecture, which lies in the subtropical zone, sporadic cases of leptospirosis due to a variety of serovars have been observed every year. In summer of 1999, clusters of suspected leptospirosis cases occurred in Iriomote and Ishigaki Islands. Followings are the results of bacteriological and serological investigations.

During September to October 1999, 23 specimens (15 from Iriomote, 8 from Ishigaki) were tested. Of them Leptospira interrogans was isolated from 9 specimens and the elevation of antibodies was confirmed in the other 6 specimens. The serovars included hebdomadis (7 specimens), grippotyphosa (5), pyrogenes (1), kremastos (1), and unknown (1). In Japan, there is no reported case of grippotyphosa and pyrogenes in areas other than Okinawa Prefecture.

Demography was reviewed for 13 males and 2 females (12 in Iriomote, 3 in Ishigaki) cases. Occupation was ranked as sea kayak and canue guide (7), agricultural worker (4), student (2), construction worker (1), and miscellaneous (1). Suspected places of infection included river and water fall (11), paddy field (2), and unknown (2). Major clinical symptoms were fever (100%), rigor (93%), headache (86%), muscle pain (57%), joint pain (50%), hyperemia in the ocular conjunctiva (50%), Jarisch-Herxheimer reaction (43%).

Such clusters of leptospirosis have not been reported previously and the reason remains unknown. The local residents and business persons in tourism, however, should know this disease. Disease information should be feedbacked to medical professionals. In order to understand etiology of leptospirosis, the disease might as well be designated as notifiable under the National Epidemiological Surveillance of Infectious Diseases.

Reported by: Masaji Nakamura, Katsuya Taira, Kiyomasa Itokazu, Jun Kudaka, and Ryuji Asato, Okinawa Prefectural Institute of Health and Environment; Masashi Narita, Okinawa Prefectural Yaeyama Hospital.

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