Coccidia is a common microscopic protozoan parasite of the gastrointestinal (GI) tract. Healthy adult dogs rarely develop diarrhea from coccidia, but puppies are commonly affected. Coccidia infections are caused by contact with contaminated feces, directly or in the environment, or ingesting prey animals. Dogs with clinical signs are treated with a prescription medication. Prompt removal of feces and frequent cleaning are the best strategies for prevention.

Cause

Coccidiosis is an infection in the GI tract caused by Cystoisospora spp. (previously known as Isospora). Dogs get infected with coccidia after ingesting a coccidia egg (oocyst) in a contaminated environment or direct contact with contaminated feces. An oocyst only becomes infective to dogs after it matures (sporulates) in the environment, which happens within a few hours after a dog defecates unsporulated oocysts in its stool. Dogs can also get infected with coccidia by ingesting prey, such as mice.

Coccidia can infect various species, but one species cannot infect another, meaning cats or dogs cannot infect one another. Humans cannot get Cystoisospora spp. from dogs.

Clinical signs

Many dogs do not develop signs of illness. Puppies are much more likely to develop signs of disease, which can be severe, leading to dehydration and, in rare cases, death.

• Diarrhea
• Bloody or mucoid stool
• Lethargy
• Weight loss
• Inappetence
• Vomiting
• Dehydration

Diagnosis

Coccidia is diagnosed by testing a fecal sample to observe coccidia oocysts. In some cases, dogs may not yet be shedding oocysts in their stool early in the course of illness, even after clinical signs have started, and may need repeat testing. Additional diagnostics, such as blood work, may be required in cases of severe illness.

Other species of coccidia, such as Eimeria spp., may be noted on a dog’s fecal test, but since dogs are not host to this species, it does not cause infection in dogs. This is often from predation or eating another animal's feces (coprophagia), such as rabbits, rodents, or ruminants.

Treatment

Many cases of coccidia in adult dogs are asymptomatic and self-limiting, meaning they do not require treatment.

Treatment for those with clinical signs of illness requires a specific medication outside the common deworming medication often prescribed for initial puppy visits. Sulfadimethoxine (Albon) is the only FDA-approved medication for coccidia in the United States. A few other medications, such as ponazuril, are often used off-label to treat coccidia with success. Coinfections with other parasites are common and may require additional medications.

Additional treatments for dogs with more severe illnesses could include fluid therapy, medications to protect the GI tract and prevent nausea, or bland diets to support the GI tract.

Because reinfection can easily occur from environmental contamination, patients should be bathed after their last treatment and the environment disinfected to minimize the risk.

Outcome

Most dogs with clinical signs of coccidiosis respond well to treatment. Reinfection may be common without proper environmental management.

Puppies that experience severe illness from coccidia may have more chance of serious complications and, in rare cases, even death.

Prevention

Coccidia can be difficult to remove from the environment completely. Once oocysts sporulate into their infective stage, they are more resistant to disinfectants. Prompt disposal of feces is critical for prevention because the oocysts sporulate within hours after defecation. Any debris left behind must be removed or scrubbed with a degreasing cleaner.

Oocysts are hardy in the environment and can survive for several months in the right conditions, and can even survive freezing. Oocysts cannot sporulate at high heat temperatures >113 F, and steam cleaning can be used to clean contaminated surfaces.

Preventing your dog from eating prey animals can also help avoid infection.