What Causes Worms in Cats? Hookworms, Tapeworms, and More

Name: What Causes Worms in Cats? Hookworms, Tapeworms, and More
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

Worms in cats come from a short list of everyday exposures: swallowing fleas, eating infected rodents or raw meat, walking on contaminated soil, or nursing from an infected mother. The type of worm usually points to the source, and the source shapes how you prevent it. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Tapeworms in cats most often come from swallowing an infected flea during grooming, and cats that hunt mice or rats can pick up a second type [1].
Hookworm larvae can burrow through a cat's skin, be swallowed from contaminated soil, or arrive inside a rodent the cat eats [2].
Roundworms pass from mother to kittens and can also be picked up from contaminated soil or prey.
Indoor cats are not automatically safe, because fleas and soil tracked indoors carry infective stages.
Yearly fecal testing (more often for kittens and outdoor cats) is the practical way to catch worms before they cause harm [3].

What Cat Worms Actually Are

"Worms" is a catch-all word for intestinal parasites you can sometimes see with the naked eye and sometimes cannot. The main ones in cats are roundworms, hookworms, and tapeworms [3]. Each has a different body plan, a different way of getting into your cat, and a different weak point when it comes to treatment.

Roundworms are long, pale, spaghetti-like worms that live in the small intestine. Hookworms are tiny and attach to the intestinal lining, where they feed on blood. Tapeworms are flat and segmented, and you may notice rice-like pieces near your cat's tail or in the litter box.

A few other intestinal worms exist, but they are less common in American cats. Whipworms, for example, are a well-known problem in dogs but are not a leading cause of feline intestinal disease in the United States. When owners search for "hookworms and whipworms in cats," the honest answer is that hookworms matter a great deal in cats and whipworms rarely do.

Signs Owners Notice

Many cats with worms look completely normal, especially early on. That is one reason routine fecal testing matters more than watching for symptoms.

When signs do appear, they tend to fall into a few groups:

Digestive signs. Vomiting, diarrhea, a potbellied look in kittens, or worms visible in vomit or stool.
Body condition changes. Weight loss or a dull, rough coat despite a normal appetite.
Blood loss signs. Pale gums, weakness, and lethargy, which are more typical of hookworm infection [2].
Bottom irritation. Scooting or licking at the rear end, often linked to tapeworm segments.

If your cat has loose stool along with a worm infection, see Cat Diarrhea with Worms: Causes and Treatment Options for a closer look at what that combination means.

What Causes Cat Worms? The Route Matters

This is the heart of the question, because the cause tells you where to aim prevention.

Tapeworms in Cats Causes

The most common tapeworm in cats, Dipylidium caninum, has an indirect life cycle. The adult worm lives in the cat's small intestine, and the larval stage develops inside an intermediate host, which in this case is a flea [1]. Your cat gets infected by swallowing the infected flea, usually while grooming [1]. That single fact explains why tapeworms and fleas so often appear together, and why flea control is tapeworm control.

A second tapeworm, Taenia taeniaeformis, uses rodents as its intermediate host. Cats with access to infected house mice, outdoor mice, or rats can acquire it [1]. This is the tapeworm of hunters, and it is far more common in cats that roam or catch prey than in cats that never leave the living room.

Hookworms in Cats Causes

Hookworms take three routes into a cat. A cat can swallow larvae from contaminated soil, eat an infected rodent, or have larvae penetrate the skin directly [2]. Infection is more common in kittens [2]. Once the larvae mature, the adult worms settle in the small intestine [2].

Geography matters here. Ancylostoma tubaeforme is the species most likely to cause illness and is found worldwide. Ancylostoma braziliense occurs in Central and South America, the southeastern United States, and Africa. Ancylostoma ceylanicum is found across Asia, the Middle East, and parts of South America, and Uncinaria stenocephala shows up in temperate and subarctic climates including Canada and the northern United States, though infections with that species are rare [2].

Hookworms also cross borders. A cat imported into Romania from the Caribbean was found to carry both A. ceylanicum and A. braziliense, a reminder that travel and adoption from other regions can change what your veterinarian suspects [4].

Roundworms in Cats Causes

Roundworms in cats causes are the most familiar to owners. Toxocara cati and Toxascaris leonina are the two species involved [2]. Kittens commonly acquire roundworms from their mother, either before birth or through nursing. Cats of any age can also pick up roundworms by eating infected prey or by contact with contaminated soil.

Roundworms are the worm most often found in young cats. In a United States laboratory review of 15,395 feline fecal examinations from 2023, Toxocara cati was the most frequently detected worm at 4.75%, behind only Giardia among all parasites [5]. A separate study of cats with no deworming history found that kittens under 6 months had the highest infection rate at 36.17% [6].

Which Worms Are Indoor Versus Outdoor Problems

Worm	Main source	Indoor risk	Outdoor risk
Dipylidium tapeworm	Fleas swallowed during grooming [1]	High if fleas are present	High
Taenia tapeworm	Infected mice and rats [1]	Low unless the cat hunts indoors	High for hunters
Hookworms	Soil larvae, skin contact, rodents [2]	Low to moderate	High
Roundworms	Mother to kitten, soil, prey [2]	High in kittens	High

The pattern is clear. Indoor cats are not immune, because fleas and contaminated soil come inside on shoes, clothing, and other pets. But hunting and free roaming raise the odds sharply for tapeworms and hookworms.

How Worms Are Diagnosed

Your veterinarian starts with a fecal examination. A small sample of fresh stool is mixed with a solution that makes parasite eggs float, then examined under a microscope. This is how roundworm, hookworm, and some tapeworm eggs are found.

Tapeworms are trickier. Dipylidium segments do not always release eggs into the stool in a way that shows up on a standard float, so veterinarians often rely on what you report seeing at home, plus a visual exam of the rear end.

Because worms are not the only intestinal parasite, modern testing may include additional methods. The large 2023 United States study used centrifugal fecal flotation, a coproantigen test, direct fluorescent antibody testing, and a Baermann examination to build a fuller picture [5]. Your veterinarian will choose the tests that fit your cat's age, lifestyle, and signs.

Routine screening is the backbone of diagnosis. Have your cat's stool checked at least once a year, and more often if you have kittens or an outdoor cat [3].

Treatment Options

Treatment depends on which worm is present, because not every dewormer covers every parasite.

For hookworms, several drugs are available, and some heartworm preventives also control hookworms [2]. That overlap is useful, because it means a monthly preventive can do double duty.

For tapeworms, treatment has to address the source. Killing the adult tapeworm without controlling fleas means your cat will simply swallow another infected flea and start over. See Tapeworm Medicine For Cats for how these products work.

For roundworms, kittens often need repeated treatment because they can be reinfected from their mother's milk while nursing.

Your veterinarian calculates the exact dose from your cat's weight and health status. Never split a dog product for a cat, and never guess at a dose from an online chart. Some dewormers that are safe for dogs are toxic to cats.

Recovery, Outlook, and Long-Term Management

Most cats respond well once the right dewormer is given. Hookworm-related anemia can take longer to resolve, and a cat that was significantly blood-depleted may need supportive care while the bone marrow catches up.

Reinfection is the real long-term issue. A cat treated for tapeworms in a flea-infested home will be reinfected quickly. A cat that hunts will keep meeting Taenia tapeworms. Long-term management is less about the medicine and more about breaking the cycle.

That means monthly parasite prevention, year-round flea control, and regular fecal testing. It also means thinking about your cat's lifestyle honestly. If your cat hunts, you can reduce but not eliminate exposure. If your cat stays indoors, you can close most of the gaps.

Prevention

Prevention follows directly from the causes.

Control fleas. This is the single highest-value step against Dipylidium tapeworm, since the flea is the intermediate host [1]. Treat every pet in the home, not just the one with visible worms.

Limit hunting and prey access. Keeping cats indoors or in a secure enclosure reduces exposure to rodents carrying Taenia tapeworms and hookworm larvae [1][2].

Manage the litter box and soil. Hookworm larvae passed in the feces of an infected animal contaminate the environment, and cats become infected by ingesting those larvae or through skin penetration [2]. Scoop daily, and cover sandboxes where cats may defecate.

Use monthly preventives. Some heartworm preventives also control hookworms [2], which makes a single monthly product a practical foundation.

Test regularly. Fecal testing once a year or more, especially for kittens and outdoor cats, catches infections before they cause illness [3].

Think about people, too. Some cat parasites can cause disease in humans. People at higher risk include pregnant women, young children, and anyone with a weakened immune system, such as people with HIV or those receiving chemotherapy [3]. If someone in your home falls into one of those groups, talk with your veterinarian about a testing and prevention plan.

Worms are not the only parasite that can look alarming on a cat's skin or in its environment. Ringworm In Cats covers a fungal problem that owners often mistake for a worm issue. And if your cat has urinary signs along with digestive ones, What Can Cause A Urinary Tract Infection In A Cat explains a separate set of causes worth ruling out.

Limitations and When to Contact a Veterinarian

No article can tell you which worm your cat has. That requires a fecal test and an examination. Individual cases need a veterinarian, and the timing below is a general guide, not a diagnosis.

Contact your veterinarian the same day if your cat:

Has pale gums, weakness, or collapses
Vomits repeatedly or cannot keep water down
Has bloody or black, tarry stool
Is a kitten with diarrhea, a potbelly, or poor weight gain

Seek emergency care now if your cat:

Is unresponsive, breathing hard, or having a seizure
Has severe, nonstop diarrhea with obvious dehydration

Schedule a routine visit if your cat:

Has rice-like segments near the tail or in the litter box
Scoots or licks the rear end frequently
Has not had a fecal test in the past year
Lives outdoors, hunts, or has fleas

Frequently Asked Questions

Can an indoor cat get worms?

Yes, indoor cats get worms. The most common tapeworm is acquired by swallowing an infected flea during grooming, and fleas come indoors on other pets, shoes, and clothing [1]. Indoor cats can also track in soil containing hookworm larvae [2].

Can I catch worms from my cat?

Some cat parasites can cause disease in people [3]. Hookworms are zoonotic, and Ancylostoma braziliense and A. ceylanicum in particular carry significant zoonotic potential [4]. Good litter box hygiene and regular deworming lower the risk.

Do I need to treat my other pets if one cat has worms?

Often yes, especially with tapeworms. Because the flea is the intermediate host, a tapeworm diagnosis means fleas are in the environment, and every pet in the home is a potential host [1]. Treat all pets for fleas at the same time.

Can worms come back after treatment?

Yes, reinfection is common when the source is not addressed. A cat treated for tapeworms but still living with fleas will swallow another infected flea and develop a new infection [1]. Prevention, not just treatment, keeps cats worm-free.

How often should my cat be tested for worms?

At least once a year for most cats, and more often for kittens or cats that go outdoors [3]. Yearly testing is also a chance to check for other intestinal parasites that cause similar signs.

References

Tapeworms in Dogs and Cats - Digestive System. Merck Veterinary Manual.
Gastrointestinal Parasites of Cats - Cat Owners. Merck Veterinary Manual.
Parasites in Cats - Cat Owners. Merck Veterinary Manual.
Imported zoonotic Ancylostoma ceylanicum and Ancylostoma braziliense infections in a cat in Romania. Parasites & vectors, 2026.
Prevalence and epidemiologic patterns of feline parasitism detected by fecal examination in the United States, 2023. Veterinary parasitology, 2026.
Prevalence, risk factors, and zoonotic potential of gastrointestinal helminths in cats: A participatory epidemiological study. Journal of helminthology, 2026.