Coccidia of the Dog

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This Vet Note is specific to Cystoisospora (formerly Isospora) spp.

What is it?

Coccidiosis is a parasitic infection of the small intestine, cecum and/or colon caused by a single-celled protozoan called coccidia. 

The most common coccidia species of the dog are Cystoisospora (formerly Isospora) spp.: C. canis, C. ohioensis, C. neorivolta and C. burrowsi

Note that there are additional coccidia species e.g. Cryptosporidium, Toxoplasma gondii, Neospora caninum, and Sarcocystis spp., but this Vet Note is specific to Cystoisospora (formerly Isospora) spp.

Eimeria spp. are not parasitic in dogs.

Where can it be found?

It can be found worldwide.

How does infection occur?

Transmission is primarily via the fecal-oral route. Infected dogs pass infective sporulated oocysts through their feces into the environment. Another dog can then become infected by ingesting an infective sporulated oocyst from the fecal-contaminated environment (direct life cycle). Another way in which infection can occur is through predatory behavior, by a dog ingesting a paratenic host (a host that harbors larvae in its tissues, e.g. rodents) containing an infective sporulated oocyst (indirect life cycle). 

What are the clinical signs?

It is commonly asymptomatic (has no clinical signs). If there are clinical signs, the most common clinical sign is diarrhea, which is usually voluminous and watery with or without mucus. Other clinical signs include bloody feces, lethargy, anorexia, weight loss, vomiting, pallor, dehydration, and abdominal pain. Although rare, it can be life-threatening. Young or immunocompromised patients are usually clinical, and are also the ones who are usually more severely affected.

How is it diagnosed? 

Diagnosis is commonly made via fecal flotation or fecal smear. Clinical signs can be present prior to oocyst shedding, and repeat testing may be required. Healthy animals can shed oocysts, and therefore shedding does not always indicate disease. Coprophagia or predation can result in shedding of nonpathogenic species (e.g. Eimeria spp. from rodents or rabbits). 

What are the treatment options?

It is commonly opportunistic, self-limiting and may not require treatment. If treatment is required, one of the medications your veterinarian may prescribe is called sulfadimethoxine. Repeat treatment may be needed. If your pet is dehydrated, additional treatment such as IV fluid therapy may be needed. It is also recommended to bathe the patient to help decrease oocysts and to additionally disinfect the environment.

A follow-up fecal flotation is recommended 1 to 2 weeks following treatment.

How can it be prevented?

Prevention consists of picking up feces promptly from the environment to help limit environmental contamination and spread of disease. Prevent your pet from coming into contact with another animal’s feces. Predation prevention to help prevent infection via ingestion of a paratenic host. Bathing your pet to help prevent reinfection. 

Can my dog infect humans or cats?

The most common coccidia species in dogs, Cystoisospora (formerly Isospora) spp., are host-specific and do not infect humans or cats. Note that there are less common species of coccidia e.g. Cryptosporidium spp. that can cause zoonosis (infectious disease transmissible from non-human animals to humans).

For Veterinary Professionals, refer to our app, VetpocketTM, for more in depth reference material including treatment dosing guidelines.

*Disclaimer: The information is not intended to replace clinical judgment or guide individual care in any matter. Please check any information and values prior to use and use at your own risk.