Coccidia in Dogs and Cats

There are numerous species of coccidia, but in dogs and cats, most infections are caused by the genus Isospora. Dogs and cats each have their own species-specific Isospora, which means that they cannot infect each other or their humans. There are some less common types of coccidia, Toxoplasma and Cryptosporidium, that can infect humans. These parasites can be carried by dogs and cats, but have also been found in the public water supply of some major cities. This can be a health risk for people who have suppressed immune systems, such as cancer patients and the elderly.

Causes of Coccidia Infections in Dogs and Cats

Dogs and cats become infected with coccidia by swallowing immature coccidia, called oocysts. Oocysts are found in feces and in soil that is contaminated with fecal material. Under the right temperature and humidity conditions, oocysts sporulate and become infective. Dogs and cats become infected by eating the feces directly, ingesting something that contains contaminated soil, or by ingesting an infected insect or mouse.

Once ingested, the infective oocyst bursts open, releasing 8 sporozoites. The sporozoites invade the host's intestinal lining cells, where they eventually develop into a new stage called a merozoite. Merozoites divide and reproduce rapidly, filling up the intestinal cell until it bursts. The merozoites that are released then go on to similarly infect and damage neighboring intestinal cells. When enough intestinal cells are destroyed, watery diarrhea results.

Clinical Signs of Coccidia Infection in Dogs and Cats

Despite the damage caused to the GI tract, most animals have subclinical infections with no detectable symptoms. Other dogs can have watery diarrhea that is sometimes bloody and can be life-threatening, especially in very young or small pets. This watery diarrhea can lead to dehydration, abdominal distress, vomiting, and in very severe cases, death.

Diagnosis of Coccidia in Dogs and Cats

Coccidia parasites are microscopic and are not visible to the naked eye. They are found on routine fecal floatation, similar to other intestinal parasites. Small numbers of coccidia can be difficult to detect, so just because a fecal sample tests negative, it doesn’t necessarily mean that the pet is not infected. Sometimes with refractory diarrhea, multiple fecal tests are necessary to get a definitive diagnosis. Infection with some of the less common types of coccidia can be diagnosed with a blood test.

Treatment Options for Pets with Coccidia

Because coccidia are not worms, they aren’t susceptible to deworming medications. The most common medications used are sulfa-based antibiotics called coccidiostats, which inhibit the coccidia’s reproduction. If the coccidia are unable to reproduce, the pet’s immune system should be able to clear the infection. This means that the length of treatment is dependent on how many coccidia there are and how healthy the pet’s immune system is. The medication is given until the diarrhea resolves, and then several additional days, usually 5-25 days.

There are newer medications called coccidiocidals that kill the coccidia outright. They can clear a coccidia infection in just a few doses and are regularly used in animals, kennels, and catteries.

Preventing Coccidia in Dogs and Cats

Oocysts that are passed in feces can sporulate and become infective in 12-36 hours. Because of this, it’s important to remove stool as quickly as possible from the environment to prevent contamination.

Oocysts are relatively resistant to a wide range of climate conditions and can survive for some time in the environment. This makes environmental decontamination an important step in dealing with a coccidia infection. If surfaces can be safely treated with bleach, add 1 cup bleach to 1 gallon of water to make an effective cleaning solution. Steam cleaning can also be used for fabrics and carpets.

When to Contact a Vet

Contact your veterinarian if your dog has had diarrhea, especially if it has blood in it, or it has lasted for more than 48 hours.

Read more:

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Hookworms in Dog and Cats

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