Cystoisospora spp

From Dog
Cystoisospora felis oocyst (blue arrow, unsporulated, about 40 µm) and a sporulated Cystoisospora rivolta oocyst (red arrow, about 20 µm)[1]

Cystoisospora spp are an ampicomplexan protozoan parasite of dogs, with prevalence rates of approximately 1 - 5% worldwide[2][3].

Species which are pathogenic to dogs include:

  • Cystoisospora felis[4]
  • Cystoisospora rivolta
  • Cystoisospora ohioensis[5]
  • Cystoisospora belli
  • Cystoisospora suis
  • Cystoisospora orlovi
  • Cystoisospora canis (syn. Isospora canis)

Although normally nonpathogenic in dogs, Cystoisospora should be considered in any dog which present with diarrhea, where this parasite appears more prevalent[6]. Infections appear to predominate in densely-housed kennels and pet shops, where infections with this parasite and Giardia spp can become endemic[7].

Diagnosis is based on coprological identification of crescent-shaped sporozoites surrounded by a thick cyst wall within a parasitophorous vacuole[8]. Isolation is maximized using 33% zinc sulfate[9].

Treatment is usually effective with metronidazole.


  1. University of Pennsylvania
  2. Beiromvand M et al (2012) Prevalence of zoonotic intestinal parasites in domestic and stray dogs in a rural area of Iran. Prev Vet Med Oct 5
  3. Tupler T et al (2012) Enteropathogens identified in dogs entering a Florida animal shelter with normal feces or diarrhea. J Am Vet Med Assoc 241(3):338-343
  4. Matsubayashi M et al (2011) Phylogenetic identification of Cystoisospora spp. from dogs, cats, and raccoon dogs in Japan. Vet Parasitol 176(2-3):270-274
  5. He P et al (2012) Cystoisospora spp. from dogs in China and phylogenetic analysis of its 18S and ITS1 gene. Vet Parasitol 190(1-2):254-258
  6. Itoh N et al (2011) Giardia and other intestinal parasites in dogs from veterinary clinics in Japan. Parasitol Res 109(1):253-256
  7. Itoh N et al (2011) Prevalence of intestinal parasites and genotyping of Giardia intestinalis in pet shop puppies in east Japan. Vet Parasitol 176(1):74-78
  8. Mitchell SM et al (2009) Development and ultrastructure of Cystoisospora canis Nemeséri, 1959 (syn, Isospora canis) monozoic cysts in two noncanine cell lines. J Parasitol 95(4):793-798
  9. Little SE et al (2009) Prevalence of intestinal parasites in pet dogs in the United States. Vet Parasitol 166:144–152