[Epidemiology of alveolar hydatid disease (AHD) and estimation of infected period of AHD in Rebun Island, Hokkaido].

An epidemiological study was performed of endemic alveolar hydatid disease (AHD, multilocular echinococcosis), Rebun Island, Hokkaido and the period of AHD infection of patients was estimated. Death certificates of the residents of the island were analyzed, and 74 deaths (43 males and 31 females) by AHD were found out of the 3,126 deaths that occurred during the period from 1948 to 1990. The red fox population of the island was estimated on the basis of past researchs. The deaths due to AHD distributed around a major peak (n = 67) between 1948-1975 and there were 7 sporadic cases between 1976-90. The red fox population on the island had been estimated to be largest in 1935. The mean infection period from initial AHD infection to death was estimated to be 26 +/- 7 years (x +/- SD) on the basis of the period between the year in which the peak red fox population was observed (1935) and the major peak of patient death (1962). The mean symptomatic period was 5 +/- 5 years, and the mean latent period from infection to the onset of AHD was 21 +/- 7 years. Sex ratio (M/F = 28/13 = 2.15) was higher (P < 0.05) at the age groups below 10 and 26-45 years than the other age groups (15/18 = 0.83), and playing outdoors during childhood and working outdoors in the prime of life were assumed to be the causes of infection.