Roundworms in Cats

Cats are infected by two different species of roundworm: Toxocara cati which is specific to cats and Toxascaris leonina which can also infect dogs and vice versa. Both species of roundworm are found worldwide and can be transmitted from pets to humans.

There is a common misconception that heavy worm burden is caused from delayed treatment- this is incorrect. A heavy worm burden is caused by repeated exposure to roundworms. The population of adult worms in a cat does not increase over time. Instead, eggs produced by adult worms in cats are shed in their feces or on their fur, which then enter the environment and can cause repeated re-infection, which in turn increases the worm burden in the infected individual.

The biggest concern with roundworm infection in cats is the impact it can have on people. Although uncommon, human infection with feline roundworm can cause two serious conditions in humans: visceral and ocular larval migrans. Generally, human infection with roundworms occurs when a person (accidentally) ingests fecal material infected with roundworms. After ingestion, the worms work their way through the body to various organs such as the eyes, lungs or liver. Rarely, they can also migrate into the brain or heart. Young, old, or immunocompromised people are at the greatest risk of these conditions. Since roundworms can infect humans, it is important to exercise proper hand hygiene after handling any animal and their feces.

Roundworm infection is very common, and rarely causes illness in healthy cats. Cats who are very young, geriatric, are immunocompromised (for example, infected with FIV or FeLV), or who are suffering from a heavy worm burden may become unwell.

While uncommon, heavy worm burdens can cause serious illness in cats, such as pneumonia and intestinal obstruction.

In rare cases, a heavy infestation of roundworms in a young or immunocompromised cat can cause sudden death.

Cats are infected by roundworms in three different ways - by ingesting larval eggs from the environment (usually by grooming), by eating a prey animal that is infected (such as a rabbit or mouse), or by nursing from a mother cat who is infected.

Roundworm infection in cats is typically asymptomatic. Usually the only indication that a cat is infected with roundworms is when an owner finds a spaghetti-like worm in the stool.

Kittens and immunocompromised cats are most likely to develop symptoms.

Diagnosis of roundworm is often by identifying an adult worm in the stool or vomit.

A fecal floatation test can also be performed if roundworms are suspected, however the false-negative results are common. Less common modes of diagnoses include bloodwork for antigen and PCR testing.

Treatment of a roundworm infection is with a prescription of a deworming medication such as pyrantel or milbemycin. This medication is usually given in several rounds over a period of months to ensure the entire worm population is eliminated. As with any medication, it is very important to administer all doses on time as directed, as missed or even late doses can lead to ineffective treatment.

During deworming treatment, it is common to see adult worms in the stool. This is because the worms are fleeing the host in response to antiparasitic medication.

Treatment is usually curative. Left untreated, cats are often infected with roundworms for their entire lives. Continuing re-infection without treatment may lead to a heavy worm burden, which can cause more serious health issues.

Roundworm infection is easily prevented, and taking preventive measures are important for all cats. Since many kittens develop infection from nursing, it is important to keep a regular deworming schedule starting from a young age. It is important to follow veterinary recommendations for deworming and checking regular fecal samples throughout life. This is especially important for breeding and pregnant cats due to the transmission routes of infection.

Veterinary review of each individual cat’s lifestyle and risk factors is important to ensure long term control of roundworm infection. Some routine parasite control methods are effective at treating roundworm, but efficacy depends on what stage of the life cycle the parasite is in. Routine diagnostics and professional guidance help ensure that new or developing parasite infections are caught and treated early, even in cases where regular parasite prevention is in place.

Keeping the environment clean is also an important preventive measure. Promptly cleaning up feces helps reduce rates of re-infection. Keeping cats indoors where they are not able to hunt outside is also an effective way of preventing infection.

Roundworm infection is an extremely common condition in cats, due to how prolific it is in nature, and how easily it is transmitted.

• Deworming medications
• Monitoring
• Environmental hygiene