Roundworms in Cats and Dogs

By Jennifer Copley (Last Updated 6 December 2011)

Roundworms, which are long, spaghetti-shaped creatures, swim freely within the intestines, causing inflammation and robbing the pet of nutrients he’s consumed. Roundworms can make a cat or dog quite ill, and even kill a very young or elderly pet. Complications may include pneumonia due to worms infesting the lungs.

How Dogs and Cats Catch Roundworms

Roundworms are transmitted by:

• Nursing from an infected mother
• Consuming hosts such as cockroaches, rodents, birds, or earthworms
• Licking contaminated soil from fur while grooming
• Eating feces (a common problem among dogs)
• Eating contaminated dirt (a behaviour caused by a condition called pica)
• Consuming eggs while eating grass (see Why Dogs and Cats Eat Grass for an explanation of this common behaviour)

Once the cat or dog has been infected, the larvae hatch within the gastrointestinal tract and then travel through the liver, muscle tissue, and lungs. Several weeks later, they return to the intestines where they mature and begin reproducing. The cat or dog then passes roundworm eggs in his stool.

Can People Catch Roundworms from Cats and Dogs?

People can catch roundworm from cats and dogs. The most common mode of transmission is by ingesting eggs from soil contaminated by dog or cat feces. This may occur when a person gardens without gloves and touches his mouth or a child plays in dirt and then eats without first washing her hands.

Up to 10,000 people per year are infected with roundworms in the United States alone. An infestation of roundworms can cause organ damage in humans, so infection is a serious health issue. Roundworms are particularly bad for children, who can suffer eye damage as a result of infection.

For symptoms of intestinal worms, as well as treatments and ways to protect your pets and human family members against infestation, see Symptoms, Treatments, and Prevention of Intestinal Worms.

For more cat articles, see the main Cats page. For more dog articles, see the main Dogs page.

This article is provided for informational purposes only and is not intended as a substitute for veterinary consultation and care.