The Importance of Deworming

Do you ever wonder why your veterinarian wants to check a sample of your pet’s feces on those routine examinations or anytime your pet is vomiting or has diarrhea? Well, it’s to look for evidence (e.g., eggs) of worms that could be living in your pet’s gastrointestinal tract. Some worms can live in relative harmony with your pet, and you may not know they even exist. But most gastrointestinal worms pose risks to your pet’s health, and some are a health threat to humans (especially children) because the eggs of these parasites contaminate the soil.

What are the clinical signs of intestinal parasites?

Signs and their severity depend on the parasite involved, the number of worms, the age and immune system of the pet, and the presence of other worms or other diseases. Clinical signs can vary from none to any of the following: constipation, diarrhea, flatulence, lethargy, poor haircoat, pale gums, poor growth rate in puppies and kittens, a “pot-belly” appearance, “scooting” on the rear end, vomiting, weakness, and weight loss. Some of these parasites can eventually cause death.

What are the common intestinal parasites of dogs and cats?

Hookworms—These very small worms are hooked on one end so they can attach to the intestinal walls and rob your pet of nutrients. Furthermore, the attachment causes damage and ulcers, which in turn cause blood loss, anemia, and pale gums. In younger animals with many hookworms, the anemia can be so severe as to require a blood transfusion or result in death. Dogs pick up the microscopic eggs and larvae when they walk or play in soil contaminated by hookworm eggs. Eggs ingested during grooming or licking develop into adult worms in the digestive tract, where they produce eggs that are passed out with the feces. When feces are left on the ground, the eggs contaminate the soil to infect more dogs and people. Hookworms can penetrate the skin, so walking barefoot across the yard or playing in contaminated sandboxes or dirt can put children (and adults) at risk of infection.

Roundworms—Larger, rounder, and longer than hookworms, roundworms are the most common parasite of the digestive tract in dogs and cats. Roundworms absorb nutrients, damage the lining of the intestines, and interfere with digestion. Almost all puppies in North America are born infected with a roundworm called Toxocara canis. Puppies can have egg-producing adult worms within their digestive tract by three weeks of age, so it is very important to start deworming pups at a young age. These eggs are also passed out with the feces and contaminate the soil, so your pet can become reinfected. Humans can also become infected by ingesting contaminated soil.

Whipworms—These one- to two-inch long worms resemble a whip—skinny on one end and stout on the other—giving them their “whipworm” name. Dogs pick up the microscopic parasite by walking or playing in soil contaminated by whipworm eggs. Eggs are ingested during grooming or licking and develop into adult worms in the large intestine. Adult worms produce eggs that are passed out with the feces, which contaminate the soil when feces are left on the ground. Although whipworm infections are fairly common in dogs, they are rare in cats.

Tapeworms—Fortunately, these large, segmented worms have minimal nutrient requirements, so they do not rob your pet of nutrients like the three other parasites discussed above. However, they may cause your pet to “scoot” on its rear end, and you may actually see segments of the worm in the feces or around your pet’s anal area. Fresh tapeworm segments are flat and about the size of a grain of rice, while dried segments look more like sesame seeds. When the segments are broken on the pet’s body, the microscopic eggs are released and consumed by flea larvae. When the flea larvae mature into adult fleas, the pet will chew or bite and ingest fleas that contain the tapeworm eggs. Other types of tapeworms (such as those found in rodents) can be ingested if your dog or cat is a “hunter.” However, flea control is the most important aspect of preventing tapeworm infections in your pet.

Adult dogs and cats should have their stools examined several times a year.

Can any of these intestinal parasites be transmitted to the rest of my family?

Diseases that can be transmitted to humans from animals are known as zoonotic diseases. Two of the four parasites discussed above have zoonotic potential: hookworms and roundworms. Hookworm larvae can penetrate and migrate thorough the skin of people, causing redness and itching; this syndrome is known as cutaneous larva migrans. Usually the lower extremities are affected. Roundworms are even more dangerous because the larvae migrate through organs such as the eyes, brain, and liver, causing significant damage, especially in children. Roundworms cause syndromes known as ocular or visceral larva migrans, depending on whether the eyes or the organs are affected.

How can I prevent intestinal parasites from infecting my dog or cat?

All puppies and kittens should have a fecal examination and should be treated for roundworms and hookworms even if the examination is negative. This is because eggs can be shed intermittently (and therefore may not show up on the day that the stool is examined) and because pups and kittens can be born with roundworm infections (transferred across the placenta or in the milk).

Adult dogs and cats should have their stools examined several times a year or anytime they have diarrhea or gastrointestinal signs. The stool sample should be fresh and can be placed in a clean plastic bag. The sample should be refrigerated until a veterinarian can examine it.

Because eggs of roundworms, hookworms, and whipworms are passed in feces and can contaminate the soil for years, feces should always be picked up. Daily removal of feces will decrease contamination of the soil with eggs and hence decrease the chances that a pet or human will pick up parasites from the soil.

Some heartworm preventives also prevent hookworm, roundworm, and whipworm infections, so while you’re preventing your dog or cat from getting heartworms, you can also protect him from getting other worms from the environment in which he walks and plays.

The Bottom Line

The fewer intestinal worms your pet has, the less chance that:

• Your pet will contaminate the environment with parasite eggs
• Your pet will reinfect himself
• A family member will get infected with roundworms or hookworms