Fig. 1. Common carp parasitized by Bothriocephalus

(Phoots by K. Yamada (1) and K. Ogawa (2))

Fig. 2. The scolex with bothria of B. acheilognathi

Parasite Bothriocephalus acheilognathi
Taxonomy Plathyhelminthes, Cestoda, Pseudophyllidea
Hosts Cyprinids including common carp (Cyprinus carpio).
Infection site Intestinal tract
Clinical signs Infected fish exhibits no external abnormality. White vermiform parasite is observed in the intestinal tract (Fig. 1).
Parasitology Parasitic body is ca. 4 mm wide, more than 10 cm long and composed of a scolex and many proglottids (Nakajima and Egusa, 1974a). A pair of bothria, which is an attachment apparatus to the gut of the host, is located in the scolex (Fig. 2). Each proglottid contains the reproductive structures, which mature gradually as proglottids move to the posterior part. Larvae (coracidia) are hatched from the eggs discharged from host’s gut and ingested by copepods (the intermediate host), resulting in prerocercoid larvae, which infect to cyprinid fishes (the definitive host).
Pathology Most of the villi intestinales are seriously destroyed. Haemorrhage, haemolysis or vesiculation occurs in the lamina propria mucosae. Affected fish do not die and continue to feed actively, though the histopathological changes are serious (Nakajima and Egusa, 1974b).
Health hazard Since this parasite is not infectious to human, it is harmless in food hygiene.
Diagnosis The parasite can be visually observed in the gut. Confirm the scolex with bothria by light microscopy.
Other information Recently, Bothriocephalus acheilognathi was introduced to Europe and U.S.A., probably by transportation of the ornamental fish. The parasite is harmful to cyprinids, which are highly susceptible to B. acheilognathi.
References Nakajima, K. and S. Egusa (1974a): Bothriocephalus opsariichthydis YAMAGUTI (Cestoda: Pseudophyllidea) found in the gut of cultured carp, Cyprinus carpio (LINNE) ? I. Morphology and taxonomy. Fish Pathol., 9, 31-39.

Nakajima, K. and S. Egusa (1974b): Bothriocephalus opsariichthydis YAMAGUTI (Cestoda: Pseudophyllidea) found in the gut of cultured carp, Cyprinus carpio (LINNE) ? II. Incidence and histopathology. Fish Pathol., 9, 40-45.