DIPHYLLOBOTHRIUM INFECTION IN ESOX LUCIUS

Abstract

This study showed that most of the summer caught jackfish or pike (Esox lucius) contained many larvae of D. latum (plerocercoids), in contrast to the winter caught fish which showed a scanty infestation. The larvae in the winter caught fish were small and frequently motionless, while those in the summer caught fish were large and quite active.When dogs were fed motile larvae from winter caught fish, very few adult tapeworms developed. Sixty per cent of the larvae contained in the summer caught fish produced adult tapeworms. This suggests that D. latum infection of the Esox fish is probably an annual event occurring in the early summer months.It is the small to medium sized Esox that contain numerous D. latum parasites. The very large fish contained so few parasites as to suggest that after a period of development the D. latum larvae (plerocercoid) in the flesh of the fish die off and disintegrate leaving no trace of their presence, and as the fish become large the procercoid form of the parasite has difficulty in penetrating the intestinal wall of the fish.