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Gastrointestinal Parasites of Cats


Andrew S. Peregrine

, BVMS, PhD, DVM, DEVPC, DACVM, Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada

Last full review/revision Aug 2018 | Content last modified Aug 2018
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Many parasites can infect the digestive system of cats (see Table: Gastrointestinal Parasites of Cats). The most common ones are described below.


Gastrointestinal Parasites of Cats

Common Name (Scientific Name)

How Contracted


Control and Prevention*

Hookworms (Ancylostoma tubaeforme, A. braziliense, A. ceylanicum, Uncinaria stenocephala)

Ingestion of larvae in environment or by eating infected rodents; penetration of skin by larvae

Often no signs; weight loss and anemia can occur.

Several drugs are available for treating hookworm infection. Some heartworm preventives also control hookworms.

Roundworms (Toxascaris leonina, Toxocara cati)

T. cati—sometimes passed from mother to kittens during nursing

Both species—ingestion of eggs or eating infected rodents

Often no signs; diarrhea, poor growth, dull coat, or a distended, swollen abdomen; worms may be vomited or passed in feces

Kittens should be dewormed on multiple occasions in the first 3 months of life; some monthly heartworm preventives will also prevent roundworm infection.

Stomach worms (Physaloptera species)

Cats eat hosts (beetles, cockroaches, crickets, mice, frogs)

Often no signs. Stomach inflammation which can result in vomiting, loss of appetite, and dark feces. In heavy infections, anemia and weight loss.

Several drugs from your veterinarian can be used to treat infection.

Ollulanus tricuspis

Cats pick up infection through contaminated vomit

Gastritis (stomach inflammation); causes vomiting minutes to a few hours after a meal

Drugs are available from your veterinarian to treat infection.

Tapeworms (cestodes), (Dipylidium caninum, Taenia taeniaeformis)

Eating infected fleas or prey animals

Most infections have few signs. Poor absorption of food or diarrhea may occur; unthriftiness.

Control requires medication to treat the tapeworms and preventing access to prey animals so the cat isn’t reinfected. Flea control is also important for D. caninum.

Threadworms (Strongyloides species)

Occurs more frequently in conditions of crowded, wet, unsanitary housing. Infective stage in environment penetrates skin; also swallowed

Bloody, watery diarrhea, emaciation, and reduced growth rate. Disease can be life-threatening in cats with a weakened immune system.

Drugs are available from your veterinarian to treat infection. Isolation of sick animals; thorough washing of pet living areas. . Use caution when handling infected pets because the worms can cause serious disease in people.

*A number of antiparasitic drugs (anthelmintics) are available to treat parasites in cats.


The large roundworms known as ascarids are common in cats, especially in kittens. The most important species is Toxocara cati, as it is both very common and will infect people. Toxascaris leonina also infects cats, but is typically much less common and does not infect people.

Infections with Toxocara cati are most likely to be acquired by ingestion of eggs passed in the feces of infected animals and by eating prey such as mice that carry the parasites. Sometimes, parasites can be passed to kittens through the mother’s milk. Adult parasites can then be found in the small intestine of kittens as early as 3 to 4 weeks of age. In kittens that have eaten infective eggs, hatched larvae penetrate the intestinal wall, travel to the lungs via the bloodstream, are coughed up, swallowed, and mature to egg-producing adults in the small intestine. However, larvae (an immature stage of the parasite) can sometimes also live within other organs of affected animals and people. Adult cats generally have some resistance to infection. However, around the time when they give birth, immunity to infection may be suppressed and significant numbers of eggs may be present in feces.

Infections are often not associated with any signs. The first indication of infection in young animals can be lack of growth and loss of condition. Infected cats can have a dull coat and often are “potbellied.” Worms may be vomited or passed in the feces. In the early stages, migrating larvae occasionally cause pneumonia, which can be associated with coughing. Diarrhea with mucus may be evident. Infection is diagnosed by microscopic detection of eggs in feces.

Several drugs are effective for treatment of roundworm infections in cats. Certain preventive programs for heartworm infection also control intestinal roundworm infections. Ideally, treatment for kittens should be started at 3 to 4 weeks of age, repeated at 2-week intervals until 3 months of age, and then continued monthly until 6 months of age. Your veterinarian will prescribe the most appropriate medication for your cat.

Because people, especially children, can become infected with roundworms, it is important to practice good hygiene (e.g., prompt removal of feces and washing of hands) in potentially contaminated areas or around affected cats.


Several types of hookworms can cause gastrointestinal disease in cats. Ancylostoma tubaeforme is the most likely to cause illness and is found globally. Ancylostoma braziliense is found in central and South America, southeast US, and Africa. Ancylostoma ceylanicum is found throughout Asia, the Middle East, and parts of South America. Uncinaria stenocephala is found globally in temperate and subarctic climates (including Canada and the northern US), but infections with this species are rare. Cats can become infected by ingesting the larvae in the environment (passed in the feces of an infected animal), by eating infected rodents, or by larval penetration of the skin. Infection is more common in kittens. When larvae mature to adults, they live in the small intestine.

Most infected cats show no signs. Anemia occasionally occurs and is the result of bloodsucking by the worms in the small intestine. Feces may become loose and have a tarry consistency. Loss of appetite, weight loss, and weakness occasionally develop in longterm disease. A diagnosis can often be made from the microscopic identification of hookworm eggs in fresh feces from infected cats.

A number of drugs and drug combinations are approved for treatment of hookworm infections. In addition, some heartworm medications also control certain species of hookworms. Deworming programs for roundworms in cats will usually also control hookworm infections.


Several types of tapeworms—properly known as cestodes—may infect cats. Adult tapeworms are segmented worms found in the intestines. They rarely cause serious disease. The common tapeworm of cats, Dipylidium, is acquired from eating fleas. Much less frequently, cats with access to infected house (or outdoor) mice and rats can acquire other types of tapeworm infections from these sources. In parts of the Middle East, southern Europe, and northern Africa, tapeworms can also be acquired by eating reptiles. Signs of tapeworm infection vary and can include a failure to digest and absorb food normally (unthriftiness), malaise, variable appetite, poor hair coat, and mild diarrhea. Often, there are no signs. Very rarely, seizures are seen. Diagnosis is based on finding tapeworm segments or eggs in the feces.

Control of tapeworms requires both treatment and prevention. Flea control is critical for tapeworm control, even for indoor cats. In addition to being exposed to fleas, cats that roam freely may also become reinfected by eating dead or prey animals. Confined animals can be reinfected by fleas. An accurate diagnosis will enable your veterinarian to provide effective advice on treating the infection and preventing reinfection. Several drugs are available for the treatment of tapeworms in cats.


Flukes (also called trematodes) are a class of parasites that can infect cats. They have a complex life cycle that can involve multiple intermediate hosts. There are several types of intestinal, liver, and pancreatic flukes that can infect cats (see Table: Types of Flukes that Infect Cats); however, infection of cats is uncommon in the US.


Types of Flukes that Infect Cats


Species (Common Name)

How Contracted


Intestinal flukes

Nanophyetus salmincola (salmon poisoning fluke); found in northwestern US, southwestern Canada, and Siberia

Cats eat raw or improperly prepared salmon and similar fish

Heavy infection causes enteritis (inflammation of the intestines). Infection is compounded by rickettsial infection carried by flukes (“salmon poisoning disease”).

Alaria species; found in North America, South America, Europe, Australia, and Japan

Cats eat hosts (frogs, reptiles, rodents)

Heavy infection can cause bleeding in the lungs (larval migration damage) or enteritis (inflammation of the intestines caused by adult flukes).

Liver flukes

Opisthorchis species; found in eastern Europe, Italy, parts of Asia

Cats eat certain fish

Longterm presence causes thickening and scarring of bile and/or pancreatic duct walls. Fluid may build up in the abdomen. Liver or pancreatic cancer has been seen in longterm and severe cases.

Platynosomum concinnum; found in southeastern US, Puerto Rico and other Caribbean Islands, South America, Malaysia, Hawaii and other Pacific islands, and parts of Africa

Cats acquire parasite by eating infected lizards and frogs

Mild cases seen as general unthriftiness. Severe cases (“lizard poisoning”) characterized by loss of appetite, lethargy, vomiting, diarrhea, jaundice, and enlarged abdomen, leading to death.

Pancreatic fluke

Eurytrema procyonis; found in eastern US

Rare; cats acquire by feeding on infected snails or possibly insects

Weight loss and intermittent vomiting, but may cause no signs.

For More Information

Also see professional content regarding gastrointestinal parasites.

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