Schistosoma spp

From Dog

Schistosoma are a Schistosomatid trematode parasite of birds and mammals in the Caribbean, South America, Africa and Eastern Asia, characterized by 'swimmer's itch' superficial dermatitis[1][2][3].

Although high levels of human-dog cross-infections are frequently observed[4], bovines are generally considered to be the most important reservoirs in terms of chemotherapy-based control programmes[5].

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[6].

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[7], 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[8].

Treatment is usually effective with fenbendazole or praziquantel.

References

  1. Zhou XN et al (2004) Epidemiology of schistosomiasis in the People's Republic of China, 2004. Emerg Infect Dis 13:1470–1476
  2. Blas BL et al (2004) The schistosomiasis problem in the Philippines: a review. Parasitol Int 53:127–134
  3. Garjito TA et al (2008) Schistosomiasis in Indonesia: past and present. Parasitol Int 57:277–280
  4. Rudge JW et al (2008) Population genetics of Schistosoma japonicum within the Philippines suggest high levels of transmission between humans and dogs. PLoS Negl Trop Dis 2(11):e340
  5. Gray DJ et al (2007) A cluster-randomized bovine intervention trial against Schistosoma japonicum in the People's Republic of China: design and baseline results. Am J Trop Med Hyg 77:866–874
  6. Lu DB et al (2010) Transmission of Schistosoma japonicum in marshland and hilly regions of China: parasite population genetic and sibship structure. PLoS Negl Trop Dis 4(8):e781
  7. Nonaka N et al (2011) Coprological survey of alimentary tract parasites in dogs from Zambia and evaluation of a coproantigen assay for canine echinococcosis. Ann Trop Med Parasitol 105(7):521-530
  8. Kato-Hayashi N et al (2010) Identification and differentiation of human schistosomes by polymerase chain reaction. Exp Parasitol 124(3):325-329