Pet cats, especially those that are very young or have other health problems, are susceptible to gastrointestinal parasites, or parasites of the digestive tract. Coccidia is one of the more common ones. 

What Is Coccidia in Cats?

Coccidia is a protozoan — a one-celled organism — not a worm, as many people think. Coccidia are microscopic, or not visible to the naked eye, and can cause a variety of health problems in susceptible animals.

There are several types of coccidia, but the most common type is a species called Isospora or Cystoisospora.

How Do Cats Get Coccidia?

Cats get coccidia by ingesting oocysts, or immature coccidia, passed in the feces of an infected cat. When the oocyst is passed into the environment, it begins to mature and is able to infect another host, or susceptible cat. This happens quickly, in hours to days. These oocysts can persist in the environment for months under the right conditions.

There are many ways a cat can ingest a coccidia oocyst and become infected with coccidia:

• Eating something in the environment contaminated with infected cat feces
• Eating prey, like a mouse or bird, that ate infected cat feces.
• Kittens can ingest mother’s infected feces while nursing.

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Most cats will eventually be infected with coccidia at some point in their lives but may not show symptoms. These cats — called carriers — can still spread coccidia through their feces, even without any obvious signs. Coccidia is more common in places where a lot of cats are in close proximity to each other, like shelters and catteries — facilities that breed cats.

What Are the Symptoms of Coccidia in Cats? 

The symptoms of coccidia infection vary widely based on the cat's age, health status, and number of parasites present. If there are symptoms, they show up 3 to 11 days after the parasite is ingested. Most healthy adult cats will be exposed to coccidia, and their immune system will clear it without the cat showing signs. Young kittens, which have an immature immune system, can sometimes have severe and life-threatening infections.

The symptoms of coccidia in cats include:

• No symptoms at all
• Watery diarrhea, sometimes with blood
• Loss of appetite or vomiting
• Mucus in the stool
• Belly pain
• Crying when defecating
• Dehydration
• Weight loss
• Potentially death in very young or very sick kittens

How Is Coccidia in Cats Diagnosed?

Most veterinarians diagnose coccidia in cats by looking at a fecal sample under a microscope. They are looking for the oocysts — the immature coccidia — which can be very small and easy to miss, so they may need to do multiple tests. Although fecal tests are much more common, PCR tests — for detecting genetic material of the coccidia — are now possible.

Sometimes veterinarians find coccidia oocysts on routine fecal tests, and sometimes they find them when sick cats or kittens are brought in for an examination.

What Is the Treatment for Coccidia in Cats?

There are two basic kinds of medications used to treat coccidia in cats:

• Sulfa drugs, also known as sulfadimethoxine or Albon (brand name). Doctors have used this medication for many years, and it's still effective. You give it to your cat by mouth, usually for at least five days but up to a month, depending on how bad the infection is.
• Coccidiocidal drugs (drugs that kill the coccidia) like ponazuril. This medication is also given by mouth and is effective with fewer doses but is a product for farm animals. It often needs to be compounded into smaller doses for cats, so ask your veterinarian if they have that option available.
• Sometimes a veterinarian will need to combine medications or add in supportive care like probiotics, special diets, and hydrating fluids to help the cat or kitten recover more quickly.

How to Prevent Coccidia in Cats

The infective coccidia oocyst can live in the environment for a long time — up to a year in some cases. Proper sanitation and cleaning of the cat’s living area is most important for prevention, especially in facilities that house a lot of cats or kittens close together. There are many things you can do to keep the area clear of coccidia oocysts:

• Pick up feces right away.
• Steam and pressure wash kennel surfaces.
• Ammonia and chlorine sanitation works, but animals can't be present during treatment due to toxicity.
• Clean all surfaces and bowls daily.
• Avoid fecal contamination in water.

Here are some other things that can help prevent coccidia in cats:

• Have your veterinarian test a fecal sample in any new kitten and yearly in older cats.
• Bring any cat with diarrhea to the vet, especially new kittens.
• In breeding facilities, test fecal samples on queens — female cats — in late pregnancy.
• Quarantine, or separate from the rest, any sick cats or kittens, especially if they have diarrhea.
• Don’t feed cats raw meat.
• Control pests like mice and rats that can carry coccidia, and don’t let your cat catch prey.
• Keep your cat indoors.

Can I Get Coccidia From My Cat? 

The type of coccidia that we've been talking about, called Isospora or Cystoisospora, is species specific. This means that cats can't spread it to other species, including dogs, people, or other animals. 

There are less common types of coccidia that can infect people, including Toxoplasma and Cryptosporidium. Toxoplasma is a concern to pregnant women, as it can cause birth defects. Toxoplasma and Cryptosporidium can cause disease in people with weak immune systems, so it’s especially important that these people take special precautions. This includes picking up cat feces right away, having someone else clean out the litter box, and washing your hands after handling your cats. There's no reason to get rid of your cat if you use proper hygiene.

Although coccidia is a relatively common gastrointestinal parasite in our pet cats, it doesn’t have to be deadly. Proper sanitation, quick treatment, and close monitoring of kittens will help keep your cat as happy and healthy as possible.