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The Causes of Worms in Cats

| Updated September 26, 2017

Worms and other gastrointestinal parasites occur in up to 45 percent of cats. The most common worms are roundworms, hookworms, whipworms and tapeworms. Single-celled organisms called coccidia and giardia are also parasites similar to worms. Worms are spread easily amongst cats, dogs, and can even be spread to people. If left untreated, certain worms can enter the vital organs of the body and cause infections.


Roundworms are the most common intestinal parasite in cats in the world and are more common in kittens. Cats often become infected with roundworm by ingesting eggs or by eating rodents that have larvae in their tissues. It is also possible to become infected by drinking contaminated water, licking contaminated fur or paws, or eating infected soil. Kittens can be infected by larvae passed through the mother's milk and often become infected soon after birth.


Adult cats can become infected by hookworm larvae that has penetrated their skin or that they ingest. While it is possible for a female dog to pass the infection along to her pups through milk, it is not possible for a female cat to pass the larvae to her kittens.


Whipworms are an uncommon parasite in cats in the United States. An infection of whipworms is passed through a cat's feces. Another cat can pick up the infection by eating infected soil or licking contaminated fur or paws.


Cats become infected with tapeworms by ingesting infected fleas while grooming or by eating infected rodents. Fleas and rodents often become infected by eating tapeworm eggs in the environment. It is also possible for tapeworms found in infected cats to cause disease in humans if the eggs are ingested.


Coccidia is a single-celled organisim contracted when a cat eats infected soil or licks contaminated paws or fur. The parasites damage the lining of the intestine and prevent cats from absorbing nutrients from its food.


Cats can become infected with giardia, a single-celled organism, by ingesting cysts present in the feces of another infected animal. The disease is most common in multiple-cat households and catteries. The infection rate is higher in kittens.