Abstract
A huge number of elvers of the European Eel were imported, as seeds for culture, from France into Japan in the spring of 1969. From the end of March to the early part of May ichthyophthiriasis broke out among them in many ponds. The parasites occurred on the body and fins, but were never seen on the gills. The disease caused no mortality in any pond and disappeared late in May.
Taking the fact into consideration that icthyophthiriasis has never been known to occur among the Japanese elvers, though the present authors found out afterwards one case of icthyophthiriasis amog large Japanese eels in a pond, the causative parasite was thought to have deen introduced, carried by the imported elvers, from France into Japan and to have multiplied explosively but temporarily.
