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Gastrointestinal Parasites of Cats

By Dana G. Allen, DVM, MSc, DACVIM, Professor and Chair, Department of Clinical Studies, Ontario Veterinary College, University of Guelph ; Sharon Campbell, DVM, MS, DACVIM, Manager, Pharmacovigilance Regulatory Affairs, Veterinary Medicine Research and Development, Pfizer Inc. ; Ben H. Colmery, DVM, DAVDC ; James G. Fox, DVM, MS, DACLAM, Professor and Director, Division of Comparative Medicine, Massachusetts Institute of Technology ; Carlton L. Gyles, DVM, PhD, Professor Emeritus, Department of Pathobiology, Ontario Veterinary College, University of Guelph ; Walter Ingwersen, DVM, DVSc, DACVIM, Specialist, Companion Animals, Boehringer Ingelheim (Canada) Ltd, Vetmedica ; Lisa E. Moore, DVM, DACVIM ; Sofie Muylle, DVM, PhD, Faculty of Veterinary Medicine, Department of Morphology, Ghent University ; Sharon Patton, MS, PhD, Professor of Parasitology, Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee ; Andrew S. Peregrine, BVMS, PhD, DVM, DEVPC, DACVM, Associate Professor, Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada ; Stanley I. Rubin, DVM, MS, DACVIM, Clinical Professor, Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois at Urbana-Champaign ; H. Carolien Rutgers, DVM, MS, DACVIM, DECVIM-CA, DSAM, MRCVS, Senior Lecturer, The Royal Veterinary College, University of London ; Jörg M. Steiner, DrMedVet, PhD, DACVIM, DECVIM-CA, AGAF, Associate Professor and Director, Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A & M University ; Thomas W. Swerczek, DVM, PhD, Professor, Department of Veterinary Science, University of Kentucky

Also see professional content regarding gastrointestinal parasites.

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

Signs

Control and Prevention*

Hookworms (Ancylostoma tubaeforme, A. braziliense, A. ceylanicum, Un-cinaria 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—commonly passed from mother to kittens during nursing

Both species—ingestion of eggs or eating infected rodents

Often no signs; diarrhea, poor growth, 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)

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; causes vomiting minutes to a few hours after a meal

Drugs are available from your veterinarian to treat infection.

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

Eating infected fleas or prey animals; the biting mite Trichodectes canis, is also an intermediate host

Most infections have few signs. Poor absorbtion of food or diarrhea may occur; unthrifty, potbellied.

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)

Infective stage in environment penetrates skin; also swallowed

Often no signs; sometimes watery diarrhea.

Isolation of sick animals; thorough washing of pet living areas. Disease is more severe in cats with a weakened immune system.

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

Roundworms

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. In kittens, infections with Toxocara cati are most likely to be acquired by ingestion of parasites in 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. Cats of all ages may also be infected with Toxocara cati by ingesting eggs that have been in the environment for at least 2 weeks, and by eating prey such as mice that carry the parasites. Maturation of parasites typically only occurs in the gastro-intestinal tract. However, 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. 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.

Hookworms

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 in southern Africa, India, and southeast Asia. Uncinaria stenocephala is found globally in temperate and subarctic climates, 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 or in the milk from a nursing queen), 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.

Tapeworms

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. The biting mite, Trichodectes canis, is also an intermediate host. 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, mild diarrhea, and a pot-bellied appearance. 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.

Flukes

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

Class

Species (Common Name)

How Contracted

Signs

Intestinal flukes

Nanophyetus salmincola (Salmon poisoning fluke); found in northwestern US, southwestern Canada, and other countries of the northern Pacific rim

Cats eat intermediate host (raw or improperly prepared salmon and similar fish)

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

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

Cats eat hosts (frogs, reptiles, rodents)

Heavy infection can cause bleeding in the lungs (larval migration damage) or enteritis (adult flukes).

Liver flukes

Opisthorchis species; found in eastern Europe, former Soviet Union, parts of Asia

Cats eat certain fish

Longterm presence causes thickening and fibrosis of bile and/or pancreatic duct walls. Fluid may build up in the abdomen.

Amphimerus pseudofelineus; reported in southern and midwestern US

Rare; cats acquire by eating infected fish

Vomiting, poor appetite, lethargy, weight loss.

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 feeding on infected lizards and toads

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

Pancreatic fluke

Eurytrema procyonis; found in North America

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

Weight loss, but may cause no signs.

For More Information

Also see professional content regarding gastrointestinal parasites.

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