Pathogenic species include:
These flukes are small (0.5 - 1.5 mm) and the anterior part of the body is flat, and the posterior part is conical. The eggs are oval, light brown, and fairly large (120 × 65 µm). The life cycle includes freshwater snails (eg, Helisoma spp) as first intermediate hosts. Cercariae emerge from the snails, penetrate tadpoles, and develop into mesocercariae. Frogs, snakes, and mice then acquire infection by eating tadpoles; the mesocercariae transfer to their tissues and remain as this life-cycle stage. Dogs and other definitive hosts become infected by feeding on these animals.
The young flukes migrate through various organs of the definitive host, including the diaphragm and lungs, before reaching the small intestine. Although the flukes are generally considered to be nonpathogenic, large numbers may cause pulmonary hemorrhages during migration or enteritis when they mature in the small intestine.
Praziquantel is considered to be the drug of choice for elimination of this parasite.
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