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Roundworms

Randy Walker DVM

About Roundworms...

The various species of roundworms (scientifically named Toxocara canis, Toxocara cati, and Toxascaris leonina) are common parasites of dogs and cats. Adult roundworms live in the small intestine. Roundworms are also commonly referred to as ascarids, puppy worms, or kitten worms. They are the most common parasites of dogs and cats worldwide.

What Are The Symptoms Of Roundworms?

The main symptoms of roundworms are a potbelly, diarrhea, gas, vomiting, lack of energy, slower growth rate, and a dull coat. If the patient has immature roundworms migrating through the lungs this can cause coughing. Patients infested with roundworms can sometimes show some or all of these symptoms. Sometimes roundworms cause no symptoms at all.

How Are Roundworms Transmitted?

Roundworms are transmitted in one of four ways: (1) Eggs passed in the stool larvate (meaning to give rise to infectious "baby roundworms'') and these larvae are ingested (meaning taken in by the mouth) by another dog or cat; (2) Eggs passed in the stool larvate and these larvae are ingested by an intermediate host (such as a mouse, bird, beetle, or earthworm) which is then ingested (eaten) by a dog or cat; (3) The puppies or kittens are infected in the womb when infectious larvae in the mother dog or cat's system pass across the placenta and infect them; or (4) The puppies or kittens are infected by ingesting the infectious larvae which are secreted and deposited in the mother's milk.

How Are Roundworms Diagnosed?

Roundworms are usually diagnosed by microscopic examination of a small amount of the patient's stool. To do this we mix a small amount of stool in a heavy saltwater solution (we use sodium nitrate). If roundworm eggs (or other parasite eggs) are present they will float to the surface. At the surface we catch the eggs on a slide and identify them under the microscope. Adult roundworms aren't often seen in the stool but when they are seen they can be quite easily detected. When adult roundworms are seen in the stool this is often because of ongoing disease in the bowel or sometimes because the worm burden had become so great that the worms are crowding each other out. In this small percentage of cases the adult worms are easily detected and diagnosed in the stool. In the overwhelming majority of cases, however, roundworms are diagnosed by detecting the eggs with a microscope.

What Is The Public Health Significance Of Roundworms?

Although it doesn't happen commonly, roundworms can sometimes infect humans, resulting in a condition called Visceral Larva Migrans. In this condition roundworm larvae migrate around in the tissue of a person's abdominal organs, causing damage to the organs which can sometimes be severe and even fatal. Since the human being is not the definitive host, roundworms will not develop into adult worms in the human. People most at risk of developing Visceral Larva Migrans are children, especially if they have been eating dirt.

How Can Visceral Larva Migrans In People Be Prevented?

This condition can be prevented by careful attention to hygiene. Make sure all pets are checked routinely (yearly) for roundworms and other parasites and de-worm the pets as needed. Don't let children eat dirt or the stool of pets.

How Are Roundworms Treated?

We have several effective medications for eliminating roundworms. Most of these are given to the pet either in an oral dose (pill or liquid) or an injection. For most cases of roundworms we give an initial treatment and then a follow-up treatment 2-3 weeks later.

Why Is It Necessary To Give A Follow-Up Roundworm Treatment 2-3 Weeks Later?

Most de-wormers will eliminate only the adult roundworms. This leaves the immature roundworm larvae (migrating through the lungs and liver). These immature forms usually take two to three weeks to develop into mature worms in the small intestine. The follow-up de-worming eliminates these worms.

If My Dog Or Cat Has Been Treated For Roundworms Can They Become Infected Again?

Yes. Reinfection is certainly possible although it's less likely in mature, healthy pets.

How Can I Prevent Re-Infection?

The best ways are to (1) Keep your pet away from areas that can be contaminated by feces from infected animals; (2) Empty the cat's litter box and pick up the dog's droppings; (3) Discourage hunting of mice, birds, or ''bugs"; (4) Have the stool analyzed routinely (once yearly).

Besides Roundworms, Are There Other Internal Parasites That My Dog Or Cat Can Become Infected With?

Yes. In addition to roundworms, your dog can pick up tapeworms, whipworms, and hookworms, (all of which are worms) coccidia (which are one-celled parasites), and giardia (which are protozoa parasites) among others. Your cat can pick up tapeworms, hookworms, coccidia, toxoplasma (a one-celled parasite), and giardia.


- Randy Walker DVM
Sun Lakes Animal Clinic
May 17,2004



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