Stan Wood, DVM, Diplomate ABVP

Specialist in Canine & Feline Practice

Coccidiosis in Cats

Coccidiosis is an infection with a one-celled organism; these organisms are classified as protozoa and are called coccidia. Coccidia are not worms; they are microscopic parasites that live within cells of the intestinal lining. Because they live in the intestinal tract and commonly cause diarrhea, they are often confused with worms.

Means of Infection

Oocysts (immature coccidia) are passed in the stool of the cat. They lie in the environment and eventually sporulate (mature) into a more developed oocyst that can infect the cat again. Other cats, dogs, or mice may also become infected. This process can occur in as little as 6 hours, but it usually takes 7-10 days. If the sporulated oocysts are swallowed, they mature in the cat's intestine to complete the life cycle. If the oocysts should be swallowed by a mouse, the cat may also become infected by eating the mouse.

Clinical Signs

Most cats that are infected with coccidia do not have diarrhea or any other clinical signs. When the eggs (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, they may cause severe, watery diarrhea, dehydration, abdominal distress, and vomiting. In severe cases, death may occur.

Diagnosis

Coccidiosis is diagnosed by performing a microscopic examination of a stool sample. Since the oocysts are much smaller than the eggs of the intestinal worms, a very careful study must be made. Infection with some of the less common coccidial parasites is diagnosed with a blood test.

Treatment

The most common drug used to eliminate coccidia is a sulfa-type antibiotic. It is given for 10-14 days. The medication is sweet tasting and objection to the taste is usually not a problem. If the sulfa-type drug is not effective, others are available. Additional medication may be needed if diarrhea and dehydration occur.

Reinfection of cats is common so environmental disinfection is important. The use of chlorine bleach, one cup in a gallon of water, is effective if the surfaces and premises can be safely treated with it.

Transmission to Humans

The most common coccidia found in cats do not have any affect on humans. However, less common types of coccidia are potentially infectious to humans. One parasite, called Cryptosporidium, may be carried by cats or dogs and may be transmitted to people. This parasite has also been found in public water supplies in some major cites. Another coccidial organism, Toxoplasma, is of particular concern to pregnant women because of the potential to cause birth defects in newborns.

These two coccidial parasites pose a health risk for immunosuppressed humans (i.e., AIDS patients, those taking immune suppressant drugs, cancer patients, the elderly). Good hygiene and proper disposal of cat feces are important in minimizing risk of transmission of all feline parasites to humans. Although there is risk of the cat transmitting these two particular parasites to humans, it does not warrant removing the cat from the household except in very rare instances.