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Coccidia in Cats: Symptoms, Causes and Treatment


A diagnosis of coccidia in cats, and especially kittens, can be worrisome. For an example: when your cat uses a litter box, it’s natural to have an interest in what’s deposited in the box. If those offerings are particularly unpleasant and foul-smelling this should be concern as it could be a possible cause of coccidia.

What exactly is coccidia and how serious is the problem?

[Before going into more detail, it’s important to realize that diarrhea is a symptom, rather than a diagnosis in its own right. Thus any cat with diarrhea, especially a young kitten, should be checked by a vet to get to the bottom…excuse the pun of the problem.]

What is a Coccidian Infection?

We are familiar with terms such as ‘bacterial’ or ‘viral’ infections, but less so with coccidian infections. Coccidia are a separate group of organisms, different to bacteria or viruses, made up of just one cell. Coccidia may be small…but trouble can come in small packages.

Within the family of coccidian, different subtypes exist. When we refer to coccidia in cats, we’re really talking about one particular type called Isospora felis. Don’t worry if you haven’t heard this name before…it’s more usual to use the general term, coccidiosis.

However, you may be familiar with another type of coccidian infection, toxoplasma. This is coccidian is similar (but different to Isospora). The former is the reason pregnant women shouldn’t clean out litter trays, because contact with toxoplasma, in rare cases can cause birth defects in children)

Fortunately, Isospora felis only infects cats, and doesn’t pose a risk to people (although it’s still a good idea to wash your hands after stroking any cat.)

What are the Symptoms of Coccidia in Cats?

The coccidia infection affects the gut and causes unpleasant stomach upsets. The wider symptoms include:

  • Poor appetite
  • Weight loss
  • Watery diarrhea, often with blood
  • Vomiting
  • Dehydration

But here’s a thing…not all cats become sick when infected with coccidia. This is because they have met Isospora in the past and built up a natural resistance to it. However, and it’s a big but, these cats may still carry infection which they pass out in poop and pose a risk to others. These are known as ‘carriers’.

Carrier cats are outwardly healthy but can infect others. This can be why a sick cat in a multi-cat household gets better but then relapses – she is re-infected by a carrier contaminating the environment.

Indeed, those cats with weak immune systems, are less able to fight off infection and more vulnerable to picking up coccidia infections. This is why kittens are especially at risk, along with older cats, those with other health problems, or feline immunodeficiency virus (FIV).

Causes of Coccidia Infection

Unfortunately, an infected cat passes microscopic cysts containing coccidia, which then lurk in the soil or general environment. The cysts are pretty tough and given the right weather conditions, can remain viable for around 12 months. So when another cat comes along and gets a cyst stuck to her fur, she grooms and swallows this cyst, and becomes infected. Her digestive enzymes then break down the outer cocoon, setting the coccidia free inside her gut.

Other sources of infection include a kitten having contact with her mother’s feces and hunting cats that eat rodents with the encysted form of coccidia in their muscles and gut.


Your vet may be suspicious of coccidian infection based on the clinical signs and age of the kitten. However, there are plenty of other parasites which can produce similar symptoms, so a workup may be needed. A sensible first step is to analyze a sample of the poop and look at it under the microscope. This helps identify any eggs, larvae, or parasites present.

However, there is a flaw in this method, because a cat won’t pass coccidia in every poop- even if she’s infected. This can give false negative results (when coccidia aren’t passed and therefore not to be seen). If the suspicion of a coccidia infection is high enough then the vet may opt to treat anyway and see what happens.

So why bother running the test ? The explanation for this is two-fold. Firstly, if the test comes back positive, that hey presto, you have a diagnosis. Secondly, it can help to identify or rule out other parasites, which require different treatment.

Coccidia Treatment for Cats

Happily, there is a coccidia treatment for cats available. Coccidia can easily be treated with a five-day course of a particular antibiotic. In addition, a bland diet for a few days helps to nurse the gut along and allow things to settle down.

However, if there are coccidian cysts in the cat’s bedding, on soft furnishings, or even on her fur, it’s perfectly possible for her to re-infect herself. Thus, having a good clean round of the home is also important.

As a rule of thumb, it’s essential to wash her bedding, clean her food bowls, and vacuum furnishings at the beginning of treatment and again at the end. And hold onto your hats because it’s also good practice to bathe the cat in order to get rid of any coccidia clinging to her coat. Good luck with that one!

In summary, finding coccidia in cats is more common than not, but it’s easily treated. Kittens are especially vulnerable given their weak immune systems, and may quickly become dehydrated. If your cat has an upset tummy then get her checked by a vet. But remember – the best coccidia treatment for cats requires maintaining good hygiene, along with medication.

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