Coccidia is one of the most common intestinal parasites found in dogs. Coccidia in dogs is caused by a microscopic one-celled organism called a protozoan and can cause severe diarrhea, weight loss, dehydration, and lethargy. In puppies, coccidia often causes bloody or mucus-coated stools or watery diarrhea. Coccidiosis is transmitted through contact with infected feces and ingestion of oocysts passed in the feces of an infected animal. The organism can live outside the host for up to two weeks but once it infects the new host it begins to reproduce quickly. The severity of symptoms depends on how many parasites are present in the intestines as well as other factors such as age, stress level, immune system health, and diet. Continue reading to learn more about coccidia in dogs!

What is coccidia in dogs?

Clinical coccidiosis is an illness caused by a protozoan, also called Isospora. In dogs, the prevalence ranges up to 50%, but the incidence of clinical symptoms (e.g. diarrhea) varies. So far, there is no evidence that coccidial infections could be transmitted to humans.

Clinical infections are more likely to occur in young or immunocompromised dogs. Infection risks may also be exacerbated by stress, concurrent infections, overcrowding, and/or unsanitary environments.

How do dogs contract coccidia?

Coccidia is transmitted through contact with infected feces and the ingestion of oocysts passed in the feces of an infected animal (i.e. fecal-oral transmission). The coccidia infection begins when a coccidian oocyst is eaten and releases sporozoites, which invade and multiply within the cells lining the small intestine. After multiplying for a few days, the coccidians rupture the cells and are shed in the animal's feces. The coccidian oocysts can survive in the environment for up to two weeks, which allows for easy transmission of coccidia between animals. Puppies are more likely to shed higher numbers of coccidia oocysts.

How is coccidia in dogs diagnosed?

Your veterinarian will perform a physical exam and ask about your dog's clinical signs and symptoms. A fecal sample will be collected and examined under a microscope for the presence of coccidia oocysts. In some cases, a blood test may also be ordered to check for an increase in white blood cells (indicating inflammation). Additionally, if your puppy has been diagnosed with coccidia, have your veterinarian also test for giardia as this parasite frequently occurs with coccidia infections in dogs.

What are the symptoms of coccidia in dogs?

The severity of coccidiosis symptoms depends on how many coccidia parasites are present in the intestines as well as other factors such as age, stress level, immune system health, and diet. Some dogs show no signs of illness, whereas others may have severe diarrhea (sometimes bloody or mucus-coated), vomiting, weight loss, and lethargy.

How is coccidia in dogs treated?

Fortunately, there are effective treatments for coccidiosis. Often, coccidiosis resolves on its own without treatment. It is also possible that treatment may reduce environmental contamination and/or resolve clinical signs more quickly.

Treatment options include sulfonamides, trimethoprim-sulfa, and triazinetrione. Sulfadimethoxine is the only currently approved therapy in North America for the treatment of coccidiosis. In general, the prognosis is good to excellent depending on how soon the dog is diagnosed and started on treatment. Prevention is key and includes good sanitation practices, prompt removal of feces, and regular deworming. Puppies may have acute or more severe symptoms that might result in death.

How can you prevent coccidia in dogs?

To decrease the presence of oocysts after treatment, it is recommended that the dog is bathed with an antibacterial shampoo.

The oocysts of coccidia are extremely resistant to most disinfectants, as well as most environmental conditions. The mechanical removal of feces and fecal debris is crucial. In order to prevent the spread of Isospora species, feces should be removed daily at the very least. This is because sporulation occurs within 24 hours. The most effective method for disinfecting contaminated surfaces is high-heat steam cleaning.


Coccidia in dogs is a common intestinal parasite and clinical disease is most common in puppies and immunocompromised dogs. Some dogs are asymptomatic whereas other dogs have diarrhea, lethargy, weight loss, and vomiting. Isospora is a common species of coccidia that affects dogs. The prognosis is good to excellent as there are effective treatments available. Prevention is key and includes good sanitation practices, prompt removal of feces, and regular deworming. Puppies may have acute or more severe symptoms that might result in death. If you think your dog may have coccidia, please contact your veterinarian for further testing and treatment recommendations. Early diagnosis and treatment of coccidia in dogs is crucial for a successful outcome!