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Roundworms

adult Toxacara roundworms

Let's start by defining what parasite means. A parasite is an organism that liveson or in another organism (known as the "host") and causes damage to the host organism. Parasites are also often carriers of viral or bacterial diseases, transmitting disease from one host to another.

Worms are dog parasites that inhabit the intestines of many animals. They are commonly found in puppies and young dogs and are ,usually, not a life threatening problem. Puppies usually acquire these dog parasites, especially roundworms, from the mother before or right after their birth.

Young and old dogs infested with fleas, or those that eat gophers, also acquire the dog parasite tapeworm. Finally, older dogs are more susceptible to dog parasites such as roundworms, hookworms, whipworms, and tapeworms.

ENDOPARASITES
These parasites (sometimes referred to as "internal parasites") live inside the host body. The most common endoparasites in our pets are the various types of worms.

In the cat, worms can invade many parts of the body. We will start our discussion with intestinal worms.

ROUNDWORMS
Most common in young kittens, roundworm larvae are usually transmitted from mother (queen) to kitten at birth or by nursing. In adult cats, transmission occurs when the cat ingests roundworm eggs from feces contaminated soil on its fur or on grass. The cat can also become infected by eating a rodent that has been eating plant material contaminated with roundworm eggs.

There are two species of roundworms affecting dogs and puppies: Toxocara canis and Toxascaris leonina. Both are treated with the same medication protocol so when eggs are seen on a fecal flotation exam it may not be necessary to determine which species is present. T. leonina can infect both dogs and cats so identifying this roundworm might be helpful in indicating which pets in the household are at risk for further contagion.

Roundworms are large, spaghetti-like worms that live in the stomach and small intestine. If present in large numbers, roundworms can actually cause a bowel obstruction. The roundworms liveon the nutrients that the cat or kitten eats causeing a nutritional deficiency for the cat. The cat may appear malnourished and have a dull, dry coat. Infected kittens often will have a "pot-bellied" appearance. The parasite can cause irritation of the stomach and bowel, resulting in vomiting and/or diarrhea. Occasionally, whole roundworms can appear in the vomitus or in the bowel movement.

There are many deworming medications available for roundworms. Some of the older medications (though still marketed over-the-counter) are harsh, causing diarrhea and or vomiting. Newer medications are more effective and gentler for the cat. Most modern dewormers kill the worms, which are then broken down and digested.

HOW INFECTION OCCURS:

  • In dogs, there are four ways by which infection with Toxocara canis occurs:
  • Consuming infective worm eggs from soil in the environment (generally through normal grooming).
  • Nursing from an infected mother dog.
  • Consuming a prey animal (usually rodent) that is carrying developing worms.
  • During embryonic development when an infected mother dog is pregnant (most puppies are infected this way).

Note: cats cannot be infected with Toxocara canis.

KEY POINTS ABOUT ROUNDWORMS

  • The fact that you do not see worms in the stool does not prove that the cat is worm free.
  • You do not need to see worms passed in the stool to prove that the dewormer worked.
  • Old deworming agents often worked by paralyzing the worms and then causing severe diarrhea to "wash" the paralyzed worms out of the system. Newer wormers do not cause diarrhea.
  • Cats must be wormed multiple times for roundworms. The dewormers kill adult roundworms only. Larval stages will continue to develop into adults. The number of wormings will depend on the prescribed medication.
  • A stool sample should be examined microscopically (for worm eggs) by your veterinarian about 3 months after deworming and yearly afterward. Any cats with vomiting, diarrhea or weight loss should have a stool sample examined to rule out worm infestation.
  • Revolution (insert trademark symbol here), a new heartworm preventative for cats, also controls roundworm infections.
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