Roundworms of the Cat

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What is it?

Ascariasis is a parasitic infection of the small intestine caused by ascarids (a.k.a. roundworms), which are large non-segmented nematodes.

Toxocara cati is the most common roundworm of the cat. Toxascaris leonina occurs less commonly.

Eggs are extremely resistant in the environment, and can survive for years. 

Where can it be found?

It can be found worldwide.

How does infection occur?

Infected cats pass unembryonated eggs through their feces into the environment. Eggs become embryonated (develop into third-stage larvae) and infectious in the environment. Another cat can then become infected by ingesting an embryonated egg with infective third-stage larva from the fecal-contaminated environment (direct life cycle). Another way in which infection can occur is by a cat ingesting a paratenic host (a host that harbors larvae in its tissues, e.g. rodents, rabbits, and birds) containing an infective third-stage larva in its tissue (indirect life cycle). Transmammary (through the mother’s milk) is possible. Migration can lead to encysted larvae within the cat’s tissues, pulmonary (lung) damage and hepatic (liver) fibrosis.

What are the clinical signs?

It may be asymptomatic (have no clinical signs). If there are clinical signs, clinical signs include diarrhea, weight loss, failure to thrive or stunted growth in kittens, abdominal distension (“potbelly” appearance), poor haircoat, vomiting, and adult worms in feces or vomitus. Intestinal obstruction, intestinal rupture, and death are rarely possible. Coughing due to lung migration is also possible.

How is it diagnosed? 

Diagnosis is commonly made via fecal flotation or freshly passed adult roundworm in feces or vomitus. Other diagnostic tools include ELISA (enzyme-linked immunosorbent assay) and PCR (polymerase chain reaction).

What are the treatment options?

Some of the medications your veterinarian may prescribe are pyrantel pamoate, fenbendazole, or milbemycin oxime.

A follow-up fecal flotation is recommended 1 to 2 weeks following treatment.

How can it be prevented?

Prevention consists of deworming pregnant and nursing queens, deworming kittens, keeping your pet on good quality anthelmintic monthly prevention, as well as picking up feces promptly from the environment to help limit environmental contamination and spread of disease. Prevent your pet from coming into contact with another animal’s feces. Predation prevention to help prevent infection via ingestion of a paratenic host. 

The Companion Animal Parasite Council recommends monitoring for disease by performing fecal flotations approximately 4 times in the first year, and then approximately 2 times per year for patients on good quality monthly prevention. 

Can my cat infect humans or dogs?

Zoonosis (infectious disease transmissible from non-human animals to humans) is possible, e.g. visceral larva migans, (VLM) and ocular larva migrans (OLM). Children typically become infected by putting contaminated soil or sand in their mouths. Cats can infect dogs.

For Veterinary Professionals, refer to our app, VetpocketTM, for more in depth reference material including treatment dosing guidelines.

*Disclaimer: The information is not intended to replace clinical judgment or guide individual care in any matter. Please check any information and values prior to use and use at your own risk.