Epidemiological features of strongyloides infection in Okinawa, Japan: Comparative study with other endemic areas.

Abstract

Epidemiological features of Strongyloides stercoralis infections in Okinawa in Japan, Chiang Mai province in northern Thailand, Khammouane province in southeast Laos and Alagoas State in northern Brazil were studied and compared. The prevalence rates of S. stercoralis infection were 9.6% (133 of 1380) in Okinawa, 47.6% (99 of 208) in Thailand, 23.8% (106 of 445) in Laos and 12.0% (32 of 267) in Brazil, respectively. Increasing age and male sex were significant factors affecting S. stercoralis infection in Okinawa and suggest that new infections from the environment do not occur in present-day Okinawa. This feature would make Okinawa a suitable area in which to investigate therapeutic efficacy without reinfection occurring after treatment. The absence of helminth infections other than S. stercoralis was an additional feature in Okinawa, where the host response and pathogenicity of S. stercoralis infection may be studied unaffected by concurrent helminth infections. Other helminth infections recorded during the survey included Ascaris lumbricoides (43.4 and 41.6% prevalence in Laos and Brazil, respectively), Trichuris trichiura (3.4, 25.2 and 44.2% in Thailand, Laos and Brazil, respectively), hookworms (24.0, 36.9 and 28.8%), Enterobius vermicularis (2.9, 2.2 and 0.7%), Opisthorchis viverrini (77.9 and 54.6% in Thailand and Laos), Schistosoma mansoni (26.6% in Brazil), Fasciola hepatica (0.4% in Laos), Taenia sp. (1.9 and 3.8% in Thailand and Laos) and Hymenolepis nana (3.7% in Brazil).