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5 Most Common Parasites & Worms in Cats (With Pictures)

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By Nicole Cosgrove


burmese cat check by vet
Image Credit: Julija Sulkovska, Shutterstock

Intestinal parasites are a very common occurrence in cats. Cats most commonly become infected by ingestion of infected feces, but there are other ways to contract the most common parasites. While there are a number of parasites that can affect your cat, the five most common parasites are discussed below (with a shout out to some not so common offenders).

Five Common Parasites and Worms in Cats

1. Roundworms

Image Credit: Rattiya Thongdumhyu, Shutterstock

What are they: When you call your veterinarian to tell them you noticed worms in your kitten or cat’s stool, roundworms are typically what everyone thinks of. As adults, these worms will be defecated out as long, white colored worms, resembling spaghetti noodles.

Roundworm eggs¹ are microscopic and can be diagnosed by most standard fecal exams. Roundworms live in the intestines, and can often cause diarrhea, inappetance, or a bloated belly. They are the most common intestinal parasite seen in cats.

How infection occurs: Cats become infected by ingesting the parasite eggs, most commonly from infected feces. However, kittens can also become infected from nursing on their mom—part of the parasite life cycle can migrate through the mom’s milk.

Other important info: It’s very important to know that these particular worms can also infect people. This is most commonly seen with kids who may play in the dirt or sand boxes used by outside cats. If there was an infected cat that defecated in these areas, your child may be infected if they then put their hands in their mouths, or have an open wound that becomes contaminated.

Treatment: Roundworms are typically easy to treat with most dewormers. Re-infection is possible, so it’s important to keep the litter box clean so that your cat doesn’t keep re-ingesting infected feces. Please speak with your regular physician or pediatrician if you believe yourself or a family member may be infected.

2. Hookworms

Image Credit: Aut Pantian, Shutterstock

What are they: Hookworms¹ are never visible to the naked eye. The worms themselves, or more commonly, their eggs, are diagnosed under the microscope. Hookworms can cause diarrhea, anorexia, and most commonly, bloody diarrhea.

As their name implies, the worms have tiny hook-like mouths that attach to the intestinal lining, causing bloody diarrhea. These hooks also aid in infection. If left untreated, cats can become severely anemic (low red blood cell count) from blood loss into the intestinal tract.

How infection occurs: Similar to roundworms, hookworms infect cats by the ingestion of contaminated feces. It is believed that kittens can also become infected by nursing on an affected mom, similar to roundworms.

Other important info: Because of the hook-like mouths, hookworms can also infect humans. They will most commonly penetrate through the skin, especially if there is an open wound, and migrate underneath the skin. It’s extremely important to always wear gloves or wash your hands when dealing with an infected cat or cleaning a litter box.

Treatment: Similar to roundworms, most dewormers will treat and kill hookworms. It’s still important to keep the litter box clean, so that your cat does not reinfect itself.

3. Tapeworms

Image Credit: Rattiya Thongdumhyu, Shutterstock

What are they: Tapeworms¹ are a fairly common parasite that can sometimes appear as “grains of rice” within the stool. The adult tapeworms may appear as long and flat “noodle-like” worms. As the worms mature, and/or the cat poops them out, they break apart and resemble small rice pieces. The eggs are not always visible on microscopic exams of the feces. Therefore, your veterinarian may just recommend deworming if your cat has a history of fleas and diarrhea.

How infection occurs: Fleas! Tapeworms need fleas as an intermediate host. Therefore cats who groom themselves and ingest fleas, groom other cats with fleas, or kill or eat rodents with fleas can become infected.

Other important info: Infection may not be noticeable for weeks, or even months, after the flea infestation. It’s also important to note that indoor-only cats can still get fleas! It is a common myth that cats who don’t go outside can never get fleas. As veterinarians, we see fleas in indoor-only cats all of the time.

Please do not, under any circumstances, purchase flea prevention over the counter for your cat. There are numerous popular products out there that you can get without a prescription—many of these can cause serious skin irritation, tremors, and even death. Always get flea prevention through your veterinarian.

Treatment: There are great dewormers that can easily kill tapeworms. However, you must get your cat on an appropriate flea preventative. If you only treat with a dewormer and decline to give flea prevention, your cat will continue to groom themselves and continue re-infection.

4. Stomach, Whip, and Lungworms

These worms are very uncommon in our domesticated cats in the United States. Your veterinarian may test for these in rare situations, but we do not commonly see them cause problems.

Please speak with your veterinarian if you are concerned your cat may have one of these more rare parasites. They are most commonly seen with outdoor-only cats, or cats who have been housed with multiple other cats.

5. Coccidia

What are they: Coccidia¹ is not a parasite, but can present with very similar signs. Coccidia are technically a protozoa, which are single-celled organisms. Under a microscope, the cysts even appear similar to certain parasite eggs. While coccidia are often misrepresented as a parasite, veterinarians often lump them together into the parasite category due to their prevalence, clinical signs, and treatment.

How infection occurs: As with a number of the intestinal parasites, cats become infected by ingesting infected feces. Often, this is from a cat who has defecated in shared soil or litter boxes. Once infected, most often kittens will develop diarrhea.

Other important info: Unlike Hookworms and Roundworms, coccidia cannot cause disease in humans.

Treatment: Because coccidia is not a parasite, it is not killed by dewormers! Nor does flea/tick/heartworm preventative do anything to help decrease the chance of re-infestation. Once diagnosed, your veterinarian will put your cat on medication to help clear the infection. If left untreated, kittens can become severely dehydrated and sick. As with intestinal parasites, keeping the litter box and environment clean will help to control re-infection.


The three most common parasites and most common protozoa in cats share similar qualities. Infection most commonly occurs by ingestion of contaminated feces, though the tapeworm needs the fleas as an intermediate host.

All of the infections can be treated once diagnosed. Preventing reinfection includes keeping the litter box clean, not allowing your cat outside, and washing your hands so that you don’t become infected as well. Regular fecal testing and regular prescription prevention (never use any OTC flea preventatives in cats) will help to drastically reduce infections in your cats.

Featured Image Credit: Julija Sulkovska, Shutterstock

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