Parasitological Findings and Epidemiological Aspects of Epidemic Amebiasis Occurring in Occupants of the Mantetsu Apartment Building, Tokyo, Japan 1

Abstract

Summary 1. This paper reports certain aspects of an epidemic of amebiasis which occurred in the Mantetsu apartment building, Tokyo, Japan. The building was a renovated six-story office building which housed 73 family units of American Occupation personnel. 2. In addition to 143 adult occupants, there were 5 children, 5 guests and 8 assigned Army personnel who were exposed to the threat of amebiasis. 3. Two hundred forty-eight (248) Japanese employees in the building were also threatened with exposure. 4. The protozoan infection rates for Americans were as follows: E. histolytica, 62.9 per cent; E. coli, 27.8 per cent; E. nana, 59 per cent; G. lamblia, 76.2 per cent; and C. mesnili, 10.6 per cent. These figures are based on adult occupants; children and guests were excluded. 5. The protozoan infection rates for Japanese employees were as follows: E. histolytica, 22.2 per cent; E. coli, 34.3 per cent; E. nana 29.0 per cent; G. lamblia, 46.0 per cent; and C. mesnili, 5.7 per cent. 6. Lower rates of protozoan infections in the Japanese were probably due to: less time spent in the building; their tea drinking customs; and authorized absenteeism for New Year's festivities during the first five days of January. 7. Exposure apparently occurred mainly during the first week of January 1947. The epidemic was recognized 23 January 1947. 8. There was no evidence that food-handlers had been responsible for the epidemic. Food-handlers were served left-over foods from the Army mess located in the building, nonfood-handlers were not authorized to receive such foods. The rate of infections indicated both groups had been about equally exposed. 9. Circumstances concerned with water and sewage systems indicated that the epidemic was waterborne. This appears to be supported by the extremely high rates of protozoan infections acquired during a brief period of exposure.