The geographical distribution of common liver flukes (the genus Fasciola) with normal and abnormal spermatogenesis.

Abstract

The geographical distribution of the common liver flukes (of the genus Fasciola) was investigated on 916 specimens collected at 34 localities in 22 countries of the world. The flukes were divided into two types, the normal and the abnormal spermato-genetic, by the number of spermatozoa in the seminal vesicle. Both Fasciola hepatica and F. gigantica from Europe, South and North Americas, Oceania, and Africa belonged to the normal spermatogenetic type which had numerous spermatozoa in the vesicle. In Asia, not only the normal but also the abnormal spermatogenetic type which has a few or no spermatozoa in the vesicle were found. Especially in Japan and Korea, only the abnormal spermatogenetic type was observed.