Canis ISSN: 2398-2942

Isospora burrowsi

Synonym(s): I. burrowsi

Contributor(s): David Lindsay




  • Phylum: Apicomplexa.
  • Class: Sporozoasida.
  • Family: Eimeriidae.
  • Genus: Isospora.
  • Species: burrowsi.

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Clinical Effects



  • Asexual stages and gametocytes are located in the epithelial cells at the tips of the villi and in the lamina propria of the posterior small intestine of dogs.
  • Cystozoites occur in the parenteral tissues, probably the mesenteric lymph nodes and the abdominal viscera, of rats, mice, probably other herbivores and probably also the tissues of the dog.


  • Intestinal development.
  • Oocysts.
  • Cystozoites in paratenic herbivorous hosts.
  • Cystozoites in tissues of dog from where reactivation and renewed intestinal infection is a likely scenario.


Direct lifecycle

  • Feco-oral transmission in kennel situations.
  • Development of the oocysts is very rapid, the prepatent period of infection is short and, as the biotic potential of Isospora is high, very large numbers of oocysts can build up rapidly to pathogenic levels.

Indirect lifecycle

  • Infection is derived by ingestion of cystozoites in the tissues of prey.
  • Numbers are unlikely to be sufficient to cause disease but this source of infection could maintain the lifecycle.

Reactivation of cystozoites in the dog

  • The presence of heavily infected animals continues to suggest that reactivation of cystozoites in immunosuppressed or stressed puppies may then initiate intestinal multiplication and so could be an important factor in causing disease.

Pathological effects

  • Some protective immunity and decreased susceptibility to infection with age probably does occur in regard to the intestinal stages.
  • No evidence for pathogenicity.

Other Host Effects

  • Obligate, intracellular parasite lying within a parasitophorous vacuole.


Control via animal

  • Remove animal from surroundings and so from source of infection.
  • There is no clear evidence that common anticoccidials have real efficacy, but they may shorten the course of the disease and therefore could be administered.

Control via chemotherapies

  • Sulfadimethoxine is approved in the US for the treatment of coccidiosis. No products are licensed in the UK.
  • Toltrazuril and diclazuril seem the most likely candidates with their proven efficacy against Isospora suis in pigs but have been used only in very few dogs.
  • Trimethoprim/sulfadiazine Trimethoprim (30-60 mg/kg in larger dogs, half this for dogs <4 kg, administered daily for 6 days). Some toxicity has been reported.

Control via environment

  • The oocysts sporulate very rapidly and are very resistant.
  • Parasite control can be difficult due to the presence of both oocyst and rodent sources of infection, and the rapid multiplication of the parasite.
  • Remove feces frequently.
  • Wash pens well to remove oocysts.
  • Desiccation will kill oocysts over several days.
  • Ammonia disinfectants will be the most effective.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lindsay D S, Dubey J P & Blagburn B L (1997) Biology of Isospora Spp from humans, nonhuman primates and domestic animals. Clin Microbiol Rev 10 (1), 19-34 PubMed.
  • Trayser C V & Todd K S Jr. (1978) Life cycle of Isospora burrowsi n. sp. (Protozoa - Eimeriidae) from the dog Canis familiaris. Am J Vet Res 39 (1), 95-98 PubMed.