What parasites cause diarrhea in cats

Of all the health topics cat owners consider, intestinal worms rarely make the list, especially if the cat stays in the home exclusively and never adventures outdoors. It is important to note however, that intestinal worms result from several causes and that we as humans can become infected if we do not manage the situation properly.

Signs to watch for when considering if your cat has intestinal parasites include:

• Intermittent diarrhea
• Little or no weight gain, despite a healthy diet
• Dull fur
• Lethargy

Understand as well that that you are dealing with several different types of parasites and that they are not all visible to the eye. As a primer on the different parasites you may be dealing with:

• Roundworms (Toxocara cati, Toxascaris leonina) are the most common type of worm to infect the animal kingdom. They are usually 2 to 4 inches long, tan or white “spaghetti-like” creatures with tapered ends. If a roundworm burden is heavy, a cat may vomit these worms or pass them whole in the stool. In addition to causing vomiting and diarrhea, roundworms can have an effect on a cat’s overall health and appearance. Kittens infected with roundworms will have a potbellied, bloated look to them and may be constantly hungry. Kittens can get roundworms from their mother through the milk.

  Roundworms are zoonotic (can be transferred to humans) and can cause an infection known as “Visceral Larva Migrans,” that may result in inflammation of muscle tissue and blindness. Cat feces should be scooped from the litter box daily and disposed of in the household trash.

• Tapeworms (Dipylidium caninum, T. taeniaeformis) are the other type of parasite that’s visible to the naked eye. Actually, what you will observe are tapeworm segments that have broken off from the adult parasite that is attached to the lining of the cat’s intestinal tract. These tapeworm pieces vary in length, are usually white and are frequently seen (while still alive) contracting and expanding around the cat’s rectum or stool immediately after elimination. Once the segments die, they will look like grains of uncooked wild rice or sesame seeds and are often found where the cat sleeps.

  The most common route of tapeworm infection occurs when the cat swallows a flea that is carrying the parasite’s eggs, but infection from mice carrying the tapeworm’s egg is also possible. The good news is that tapeworms cannot be directly transmitted from cats to dogs or humans as fleas must be involved in the lifecycle process. De-worming can be done by either oral medication or by injection. Effective flea prevention will help prevent tapeworms.

• Hookworms (Ancylostoma tubaeforme) Blood-sucking intestinal parasites, hookworms have the ability to cause anemia, and sometimes death, in cats. Hookworms cannot be seen by the naked eye, and the severity of adverse effects will depend on the amount of worms in the intestine, the animal’s overall health, age and acquired immunity. Cats can become more resistant to hookworms as they grow older. Larval migration from contact with stool contaminated soil is a common cause.
• Coccida (Isopora felis) This parasite is not a worm, but a single-cell microscopic organism that will wreak havoc in a cat’s intestinal tract when present in great numbers. This protozoan will cause watery diarrhea in young and susceptible animals that have immature or compromised immune systems. In some cases, the diarrhea can be severe enough to be life-threatening.

It is important to know that most cats will require time to show signs of intestinal parasitism. The initial step in parasite control is having a stool sample tested by your veterinarian. Positive fecal exam results will determine the proper medication recommended for purging that particular worm. Be sure to consult your veterinary care professional before proceeding with any medication and never use a de-wormer on a cat that is otherwise sick, pregnant or debilitated. Worms are a health risk for sure, but properly treated can be cured effectively.

Coccidia are tiny single-celled parasites that live in the wall of your cat’s (or dog's) intestine. They are found more often in kittens, but they can also infect older cats.

Cats become infected by swallowing soil that contains coccidia or other substances in the environment that may contain cat feces It is also possible that rodents could eat the coccidia and contract a “resting” stage of the parasite. Cats that are old enough to hunt could then be infected when they hunt and eat these animals. Cats are more likely to get infected with coccidia by this method than dogs are.

How will coccidia affect my cat?

Coccidiosis, the disease caused by coccidia, is usually more serious in kittens but can occur in older cats. The most common sign of coccidiosis is diarrhea.  Severe infections, especially in kittens, can kill them.

How do I prevent my cat from getting coccidia?

Coccidial infections can be prevented by cleaning your cat’s litter box regularly and by preventing your cat from hunting. Because coccidia are found most often in kittens, it is important to have kittens examined for the parasite as soon as possible. Your veterinarian can perform a fecal test to diagnose coccidiosis. If your cat is infected with coccidia, your veterinarian is able to give it effective medications.

Can my dog get coccidia from my cat?

A cat that is infected with coccidia cannot pass the infection to dogs and vice versa. Coccidial infections in cats occur only by swallowing the coccidia in soil or cat feces or by eating intermediate hosts.

For veterinary professionals, more detailed information on coccidia can be found at https://www.capcvet.org/guidelines/coccidia/.

Giardia is a single-celled organism classified as a protozoan. It can live in the intestines of cats (and other animals, including dogs and humans) and cause severe gastrointestinal disease. It is spread by fecal-contaminated water, food, or soil.

Giardia is found worldwide and in every part of the United States.

Symptoms of Giardia in Cats

Giardia is primarily a disease that causes a lot of severe, watery diarrhea. Giardia in cats can also cause:

You will probably notice an irritated perianal region and excessive grooming to keep clean, which is unfortunately a source of continual reinfection.

It is also worth noting that cats (and other animals) can have the protozoa present in their intestines and still not show any symptoms. It is not known how often this is the case, as Giardia is not routinely tested for in cats unless they have diarrhea.

Causes of Giardia in Cats

Giardia is a protozoan that must be orally ingested. Cats are infected by the cysts by ingesting stool or contaminated soil (via grooming) or drinking contaminated water. Contaminated food is less often a source of Giardia for indoor cats but can be a source of infection for outdoors cats.

How Vets Diagnose Giardia in Cats

Your veterinarian will gather a complete history and conduct a physical exam to evaluate your cat’s hydration status and check for intestinal pain. A quick test for Giardia is available through your veterinarian’s office. They will likely need to do a fecal test for other intestinal parasites.

Treatment for Giardia in Cats

Medications for the eradication of Giardia are readily available and affordable. Metronidazole, an antibiotic, is most often prescribed. Additional medications may be prescribed depending upon the severity of the infection and the cat’s condition.

The disease can take multiple rounds of treatment, as cats may continually reinfect themselves through frequent grooming (ingesting cysts on their fur) and other sources of environmental contamination.

Recovery and Management of Giardia in Cats

Because cats that have been treated have no “immunity” against future infection, they can easily be reinfected. Therefore, all living areas that the cats have access to should be disinfected. Ammonia, dilute bleach solution, or steam cleaning can be effective. It is the impracticality of disinfecting entire households that makes this parasite a tough one to eliminate.

If there are other pets in your household, medications may be administered to them as a preventive measure. Contaminated soil or areas can remain infective for months under the right conditions, so avoiding those areas when at all possible is advisable. 

Multiple negative tests are necessary to ensure the disease has passed, as cysts are not always shed and detected on the test. And when bringing a new pet home, it is always encouraged to have an exam and stool check for parasites as well as Giardia testing before bringing the pet home and around other animals.

Giardia in Cats FAQs

Does Giardia in cats go away?

No, Giardia is a protozoal infectious agent that will not resolve on its own. Oral medications are the recommended treatment, and Giardia does not “run its course,” as a common cold does.

Is Giardia hard to get rid of in cats?

With the appropriate medication and dosage, most cases of Giardia in cats are not hard to clear, though they do require consistent treatment, strict compliance in decontaminating the home environment, and retesting to ensure the parasite is eradicated.

How long does Giardia last?

Giardia will last until it is treated and eradicated. The environment must also be decontaminated or the pet can become reinfected.

Is Giardia contagious in cats?

Yes, Giardia is passed in the stool of infected cats. The life cycle is fecal-oral, which means another cat would have to ingest the cysts from the environment. Keep in mind that cats are fastidious groomers, so you can imagine how the disease is spread easily.

Can my cat give me Giardia?

Yes. Giardia can cause diarrhea and disease in humans. If your cat is diagnosed with Giardiasis, environmental disinfection is important for your own health and safety, as well as preventing recurrence in your cat and any other pets.

Is Giardia painful for cats?

Yes. Cramping and diarrhea are as painful for cats as they are for humans.

Is Giardia fatal in cats?

If untreated, Giardia can be fatal, especially in kittens. Its dehydrating effects can be quite severe.

What happens if Giardia goes untreated in cats?

Cats can have painful cramping and diarrhea as well as dehydration and other symptoms if Giardia is not treated. In kittens or smaller cats, Giardia can cause death from dehydration.