Coccidiosis in Cats

What is coccidiosis?

Coccidiosis is an intestinal tract infection caused by a one-celled organism (protozoa) called coccidia. Isospora species are the most common type of coccidia and are sometimes called Cystoisospora. Because coccidia live in the intestinal tract and can cause diarrhea, they are often confused with intestinal worms, but coccidia are not worms. They are microscopic and act as parasites that live within the cells that line the intestine.

How did my cat become infected?

Your cat most likely became infected with coccidia from swallowing oocysts (immature coccidia) that are found in cat feces and any environment contaminated with feces. Oocysts are passed in the stool of an infected cat. They live in the environment and eventually mature into more developed oocysts that can cause infection or reinfection. This maturing can occur in as little as eight hours but usually takes seven to ten days. The more mature form of oocysts is infectious to other mammals, such as mice, as well. If your cat swallows the oocysts, they mature in the intestine to complete the life cycle. If a mouse swallows the oocysts, they encyst in the mouse’s organs, and your cat may become infected by eating the infected mouse.

Kittens are commonly diagnosed with coccidiosis, not born with it. After birth, kittens can become infected by their mother from exposure to her feces, especially with the tendency of kittens to explore. Coccidiosis is of particular danger for kittens since their immune system is underdeveloped. If the mother is shedding oocysts, her babies can ingest them during nursing.

"...kittens can become infected by their mother from exposure to her feces...'

Since young kittens (less than six months of age) have no immunity to coccidia, the organisms can reproduce in great numbers, which may have serious consequences. It takes about 3-11days for illness to develop after the kitten first ingests coccidia. Consequently, kittens that become sick from a coccidia infection are at least two weeks old.

Although most cases are the result of infection from the mother, this is not always the case. Any infected kitten is contagious to other kittens. In breeding facilities, animal shelters, kennels, and other areas where numerous pets may come into close proximity with one another, it is wise to isolate infected animals from those that are not.

What are the clinical signs of coccidiosis?

Many cats who are 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.

How is coccidiosis diagnosed?

Coccidiosis is diagnosed by performing a microscopic examination of a stool sample. Infection with some of the less common coccidial parasites may be diagnosed with a special blood test.

How is coccidiosis treated?

The most common drug used to treat coccidiosis is a sulfa-class antibiotic, sulfadimethoxine (Albon®). It is typically administered for 5-20 days. Some formulations of this medication are pleasant tasting and most cats will readily accept them. If the sulfa drug is not effective, other treatments are available, including sulfa antibiotics combined with another drug, amprolium (Albac/Amprol Hi-E®), or off-label use of ponazuril (Marquis®) or toltrazuril (Baycox®). Additional supportive treatments may be needed if diarrhea and dehydration occur.

"Cats are frequently reinfected from the environment..."

Cats are frequently reinfected from the environment, so disinfection is important. The oocysts are very resistant to environmental conditions and disinfectants. The use of diluted chlorine bleach, one cup (250 ml) of bleach mixed with one gallon (3.8 L) of water, is effective. Be sure to test clean a small area of any affected materials since bleach can damage many surfaces. Steam cleaning may also be used to destroy oocysts. Be sure to remove any feces as quickly as possible from the environment to prevent reinfection.

Can I get coccidiosis from my cat?

The most common species of coccidia found in cats do not infect humans. Some of the less common species, however, are potentially infectious. One of these organisms, Cryptosporidium, may be transmitted by cats to people, especially those with compromised immune systems. Cryptosporidium has also been found in public water supplies in some major cities. Another coccidian organism, Toxoplasma, is of particular concern to pregnant women because of the potential to cause birth defects. However, most human cases of toxoplasmosis are the result of eating contaminated meat as opposed to contact with cat feces (see handout: Toxoplasmosis). These two coccidian parasites pose an increased health risk for immunosuppressed people (i.e., patients with immunosuppressive illnesses, those taking immune suppressant drugs, cancer patients, and the elderly).

Good hygiene and proper disposal of cat feces are important in minimizing the risk of transmission of all feline parasites to humans. Although there is a risk of the cat transmitting these two parasites to humans, it does not warrant removing the cat from a home except in very rare instances, since transmission can be prevented by practicing good hygiene.

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