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What are roundworms?

Roundworms are one of the most common intestinal parasites of dogs and cats. As the name implies, these worms are large, round worms averaging 3-6” in length. These worms do not attach to the intestinal wall, but instead survive in the intestine by freely swimming. They can be an important cause of illness, especially in puppies and kittens. They can also be dangerous to your family.

The three most commonly diagnosed roundworms include Toxocara canis (dogs), Toxocara cati (cats), and Toxascaris leonina (dogs and cats).

How did my dog or cat get roundworms?

ost commonly, puppies get roundworm infections from their mother before birth. Both puppies and kittens can also be infected with T. canis or T. cati through their mother’s milk during nursing. Adult dogs and cats are infected after swallowing roundworm eggs in the environment. The larvae (immature worms) hatch in the stomach and intestines and travel through the muscle, liver, and lungs before migrating back to the intestines to mature. Once they reproduce, new eggs are passed in the stool and the life cycle of the parasite is complete. Roundworm eggs are quite common in the environment, especially in environments contaminated with feces from dogs, cats, or even wild animals such as raccoons. In addition, cockroaches, earthworms, and rodents (intermediate hosts) can harbor roundworms and serve as a source of infection for your pet. Surprisingly, up to 15% of potting soil can contain roundworm eggs, so even indoor cats have potential exposure.

What are the clinical signs?

While these parasites are often asymptomatic in adult dogs and cat, large numbers of worms can lead to life-threatening problems in puppies, kittens, or ill pets. Weight loss, decreased appetite, vomiting, diarrhea, poor growth, and a potbelly appearance are the most common signs in these animals. Death is rare, but can occur.

How are roundworms diagnosed?

Roundworms are diagnosed by microscopic examination of your pet’s stool. Since your veterinarian is searching for eggs and shedding of eggs can be intermittent, more than one sample may be necessary to make a diagnosis. Occasionally, mature worms can be found in your pet’s stool or vomit.

How are roundworms treated?

Fortunately, treatment is safe, simple, and relatively inexpensive. Deworming medications (anthelmintics) are given for 2-3 treatments at 2-3 week intervals. Because the medication essentially anesthetizes the parasites, these parasites are often visible in the stool after treatment and may still be alive. It is also important to note that none of these treatments will kill the migrating larvae or immature forms of the parasite, so repeated treatments or administration of a monthly preventative medication is necessary to completely eliminate the infection.

How can I prevent infections?

1) Puppies and kittens should receive deworming medication at a young age. Often, breeders will begin deworming puppies and kittens even before they go to their new homes.

2) Larvae can survive in the environment for months and are highly resistant to most disinfectants and even to harsh environmental conditions. Prompt disposal of all feces is important, especially in yards, playgrounds, and public parks. Litter boxes should be scooped daily and cleaned thoroughly once weekly. A mixture of dilute bleach (1:10 dilution) can be used to clean litter boxes and contaminated toys or kennels. Always wash your hands thoroughly after handling feces or cat litter.

3) For those animals that hunt or are exposed to other dogs or cats regularly, monthly preventative therapy with Heartgard Plus/Tri-Heart Plus (dogs) or Revolution (cats) is necessary to prevent repeated infections. In addition, all pets should have a fecal intestinal parasite examination performed at least 1-2 times per year.

4) Control of insects and rodents will help eliminate intermediate hosts that can serve as a source of infection.

Are roundworms dangerous to humans?

Yes, roundworms can be a health risk for humans. A study in 2007 showed that 14% of the U.S. population was infected with roundworms from dogs and cats. Children and immunocompromised individuals, in particular, are at risk for health problems should they become infected. The roundworm larvae can migrate through the body damaging the lungs, liver, brain, and eyes. Unfortunately, roundworm infection can be a cause of blindness in young children.

Infection in humans occurs by ingesting roundworm eggs in contaminated feces or soil. Clean up your pet’s feces daily and wash your hands thoroughly after handling feces or anything potentially contaminated with feces. Children’s sand boxes should be covered when not in use and caution should be exercised when your children are playing in public parks or other potentially contaminated areas.

All animals should be on a year round parasite preventative to prevent infection. We offer Heartgard Plus or Tri-Heart Plus for dogs and Revolution for cats. Protecting your pets will protect your family.

Content prepared by St. Francis Animal and Bird Hospital, 1227 Larpenteur Ave. West, Roseville MN. 55113