Although high levels of human-dog cross-infections are frequently observed, bovines are generally considered to be the most important reservoirs in terms of chemotherapy-based control programmes.
The Schistosomatidae family also includes Heterobilharzia americana found in North America.
Schistosoma spp involve two obligatory host stages, with asexual reproduction within a molluscan host (snails) and sexual reproduction within over 40 species of mammalian hosts.
Two free-swimming larval stages are recognized, with a cercarial stage released from a mollusc and then infective to a mammals, and a miracidial stage hatched from eggs passed in a mammal's faeces, then infective to molluscs.
The sexes of Schistosoma are separate, with a slender female lying in the gynecophoric canal of the large male.
Their eggs lack an operculum, unlike other trematodes and contain a fully developed miracidium when discharged from the feces or urine. The eggs hatch on exposure to water
Species which are pathogenic to dogs include:
- Schistosoma japonicum
- Schistosoma suis
- Schistosoma mansoni
Although eggs of this genus of parasite are commonly found in coprological surveys, they rarely cause disease except when venous migration into the mesenteries or urinary bladder occurs.
Clinically infected dogs are usually asymptomatic, but diarrhea or cystitis have been reported.
Diagnosis is based on coprological identification of eggs using 0.85% NaCl sedimentation techniques as well as PCR analysis of fecal samples.
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