Atlas of livestock parasites
digitized collection of microscopical preparations

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Heterobilharzia americana



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Distribution: Southeastern United States.        

Host: Mesenteric and hepatic portal veins of dogs and various wildlife species.             

Life Cycle: Eggs released in the feces of dogs produce ciliated larvae (miracidia) that develop in a snail intermediate host. Cercariae that are released from the snail intermediate host infect dogs and wildlife through direct skin penetration.                

Diagnosis: Eggs can be detected by sedimentation examination of feces in saline (or 5% formol-saline). It is important to use saline in the procedure because eggs are stimulated to hatch when they contact water. The free-swimming miracidia larvae can be observed by placing the sediment in water after performing the sedimentation procedure with saline.                

Size: Eggs 74–113 × 60–80 µm   

Clinical features: Infection with H. americana in dogs is uncommon in most areas. Infection can cause chronic diarrhea, anorexia, and emaciation. Heterobilharzia also has zoonotic importance as one of the causal agents of cercarial dermatitis (swimmer’s itch) in humans.     


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