[Estimation of the asymptomatic latent period of alveolar hydatidosis in patients infected in foreign endemic areas].

Alveolar hydatidosis (AH) is a parasitic disease with an extremely long latent period which has an important role in the endemic of human AH. The individual and average latent periods of human AH were estimated from the case histories of 19 male patients who were infected in foreign endemic areas and diagnosed surgically and pathologically as having AH after returning to Honshu, mainland of Japan. The beginning (A) and the end (C) of stay in foreign endemic areas of AH, and the midpoint (B) between (A) and (C), the time of onset of symptoms (D) and death (E) of AH were determined in the case reports. The period (D-B) from the midpoint (B) to the onset of symptoms (D) was considered as an individual latent period of AH, and the average latent period was estimated from D-B periods. The individual latent periods ranged from 3 to 44 years, and the average was 20 +/- 10 (mean +/- SD) years in the 19 cases. The average latent period was longer in 7 surviving cases (26 +/- 12) than in 12 fatal cases (16 +/- 7) at the publication of the case reports, but there was no statistically significant difference between them. The estimated latent period in this report was very close to that by Doi et al. (2000), and the traditional 5-15 years should be changed to 7-35 years.