Coccidiosis in dogsCoccidiosis in Dogs

Coccidia are protozoan parasites that affect the gastrointestinal tract of cats, dogs and many other animals. Infection is often mild and asymptomatic, but can be debilitating and severe in neonatal animals, or those with compromised immune systems.

Common nameCoccidia Scientific name: Coccidiosis



Although all dogs and cats are susceptible, the infection is most severe in very young animals (less than one month), and in animals that are immunocompromised.


Coccidia in dogs is extremely common, but due to the generally mild nature of the disease, incidence and prevalence are not well studied.

Geographic distribution

Coccidia in dogs occurs worldwide, wherever dogs are found.

Clinical signs (primary most to least frequent, scientific term, synonyms) Often none, watery diarrhea, sometimes bloody.

Cause (scientific, common term)

Various species of the genus Isospora infect dogs and cats, notably Isospora canis and Isospora felis. Coccidia is a term referring to many similar genera.

Organ systems affected (most to least affected) Small intestines, extraintestinal tissue, diagnostic tests, oocysts identified with routine fecal floatation exams.

Differential diagnosis Diarrhea from other causes: viral, bacterial or dietary.


Coccidia are parasites that live within the cells of a wide variety of domesticated species, typically inhabiting the intestines where they may cause diarrhea.

Coccidia are largely host specific, meaning cat coccidians do not infect dogs and vice-versa, although each animal can be infected by several distinct species of coccidia.

Infection is extremely common, but can be subclinical (showing no signs of illness) in healthy adult animals, and can be an incidental finding on fecal exams. Puppies and kittens less than one month and individuals with compromised immune systems can have severe disease with watery or bloody diarrhea, weight loss, vomiting or even death.

The life cycle of coccidian is quite complicated. Oocysts, which are the life stage that is stable in the environment, are ingested by the dog or cat directly, or by an intermediate host (e.g. mouse) where the parasites develop partially, then form dormant tissue cysts. If a cat or dog then consumes the intermediate host, the coccidia can complete their life cycle.

Once inside the cat or dog, the coccidia go through several stages of division within intestinal cells, ultimately causing them to rupture. New oocysts are produced and shed in the feces, completing the coccidian life-cycle. Dogs and cats can have relapses of coccidiosis from parasites that encyst within tissue outside of their intestines and re-emerge during times of stress to produce active disease.


Home Care Many infections are mild and self-limiting, with minimal supportive care being all that is required, but if signs of dehydration occur or the diarrhea lasts more than a few days, a trip to a veterinarian is recommended.

Professional Care When serious enough to require treatment, coccidiosis is usually treated on an outpatient basis with sulfadimethoxine (Albon), a drug that interferes with the coccidian life cycle enough to allow the immune system to clear the infection. It is important to note that a functional immune system is still required for the therapy to be effective. Treatment failures may point to a defective immune response.

Newer treatments, such as the equine drug Ponazuril (Marquis) are gaining popularity to treat coccidia, but are not currently licensed for use in dogs and cats. Ponazuril has the advantage of a shorter course of therapy because it actually kills the coccidia directly.

In very severe cases of coccidia in dogs hospitalization may be required for rehydration and supportive care. Underlying diseases often accompany these extreme cases in adult animals.

Action Supportive care and anti-protozoal drugs are the hallmarks of treatment for coccidiosis and are usually all that is required. Swift recognition and treatment of the disease for neonatal animals is important to avoid life-threatening dehydration.

Coccidiosis is often associated with unsanitary conditions where fecal-oral contamination is possible, so basic sanitation should be practiced at all times especially in crowded environments like kennels or catteries.

Outcome In the vast majority of cases, coccidiosis is mild disease with a good prognosis.