Coccidia is a one-celled organism (protozoa) that causes an intestinal tract infection called coccidiosis in cats. Cats can become infected with coccidia by ingesting oocysts (immature coccidia) that are found in cat feces and any environment contaminated with feces. Most cats, particularly those who spend time outdoors, pick up this parasite from their environment, grooming it off their fur and feet. Mice, rats, and other common prey species are known as transport hosts because they can carry certain life stages of coccidia, which then infect the cats who hunt them. Cats who share a litterbox with an infected cat risk picking up the parasite themselves, even if they do not hunt or go outside.

Many cats infected with coccidia do not have diarrhea or any other clinical signs. When the oocysts are found in the stool of a cat without diarrhea, they are generally considered a transient, insignificant finding. However, in kittens and debilitated adult cats, coccidiosis can cause severe watery or mucousy diarrhea, dehydration, abdominal distress, loss of appetite, and vomiting. In severe cases, death may occur.

Coccidiosis is usually eliminated in cats with an oral antimicrobial medication. Sulfadimethoxine (Albon) is the most commonly used product, though there are other medications that may be recommended. Depending on the severity of the cat’s illness, antimicrobial treatment is often combined with medications to help alleviate symptoms, such as probiotics, low residue diets, anti-nausea medications, and fluid therapy.

Cats infected with coccidia cannot pass the infection to dogs and vice versa. Coccidial infections in cats occur only by swallowing oocysts that are found in infected feces or any environment contaminated with infected feces. Proper hygiene is important to prevent the spread of coccidia. Cleaning the litter box regularly, preventing cats from hunting, and having kittens examined for the parasite as soon as possible are some ways to prevent coccidial infections.