Causative agent of dicrocoeliosis
The lancet liver fluke (0.5-1.0 x 0.2 cm) (Fig. 10.6b), a bile duct parasite in sheep, cattle, and other herbivores, occurs frequently in regional foci in the northern hemisphere (for instance southern Germany, Austria, Switzerland, North America). Its life cycle includes two intermediate hosts (terrestrial snails and ants). Humans become infected accidentally when they ingest ants containing infective metacercariae of the lancet liver fluke. Such infections are rare and either run an asymptomatic course or manifest in mild abdominal and hepatic symptoms. Diagnosis is based on detection of eggs in stool (about 40 x 25 im, oval, dark brown, containing a miracidium with two rounded germinal cells) (Fig. 10.1. p. 543). Ingestion of contaminated beef or mutton liver can result in egg excretion in stool without infection (intestinal passage). The eggs of Opisthorchis and Clonorchis must be taken into consideration for a differential diagnosis (Fig. 10.1). Praziquantel has been shown to be effective against Dicrocoelium in animals (see also opisthorchiosis).
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