CHANGING RISK OF SCRUB TYPHUS IN RELATION TO SOCIOECONOMIC DEVELOPMENT IN THE PESCADORES ISLANDS OF TAIWAN1

Abstract

Long term changes in risk of Rickettsia tsutsugamushi infection among civilian residents of the Pescadores Islands of Taiwan were associated with changing social conditions. Age specific incidence rates of scrub typhus in the Pescadores before 1940 were highest among children under 5 years of age. Rickettsiae can be demonstrated in vectors, wild animals continue to be infected and scrub typhus occurs in military personnel. A serologic survey for antibody to R. tsutsugamushi was conducted during 1975 and 1977 and failed to show evidence of previous infection among children. Two events appear to be associated with the decreased incidence of rickettsial infection in the young: increased urbanization and increased enrollment in schools. Both changes accompanied socioeconomic development which took place in the islands during the past 50 years. Prevalence of antibody to R. tsutsugamushi continues to be equal in the sexes and is undoubtedly due to similar occupational exposure of both sexes in fields and farms where vectors are numerous. The absence of apparent morbidity due to scrub typhus among the civilian populace was attributed to the mild nature of the disease caused by Pescadores strains, misdiagnosis and a lack of obligatory reporting.