What to Do When Your Dog Has Worms

4 min read

By Carol McCarthy

You might not want to think about it, but your dog likely has had worms at some point in his life, and may even have them now. If your reaction to this is an emotive “Ick,” you are not alone. But don’t let squeamishness get in the way of protecting your dog. Left untreated, these parasites, which can infect your pet’s intestines, heart, lungs, and other parts of the body, can sicken and even kill your dog, and can quite possibly infect you, too.

Dr. Cindi Cox, head shelter veterinarian with the Massachusetts Society for the Prevention of Cruelty to Animals in Boston, said studies have shown that virtually all puppies are born with roundworm infections. Cox said research has also shown that up to 30 percent of all dogs shed worm eggs into their environment.

Dr. Neil Marrinan of Old Lyme Veterinary Hospital in Connecticut added that dogs who are shedding parasites in their feces can contaminate the dirt in your yard.

Signs of Worm Infection in Dogs

Signs of intestinal parasitic infection include lethargy, diarrhea, and vomiting, said Cox, any of which could indicate a number of other health issues, so an accurate diagnosis requires a visit to your veterinarian.

In addition to a physical exam, your vet will take a stool sample to determine if worms are present and what type your dog has. It’s also important to note that dogs can have worms without having any observable symptoms. Therefore, veterinarians often recommend a fecal examination as part of a routine wellness check.

Treatment for Worms in Dogs

It is important that pet parents treat their dogs and puppies for worms, both because of their prevalence and their potential to infect humans as well, Cox noted.

Worms in dogs pose a real risk to humans, especially possible cross-infection to children. Roundworm infections in children can cause liver disease, lung disease, blindness, and other problems, Cox cautioned.

To get the jump on parasites, Cox said all puppies should be treated with a broad-spectrum de-wormer at two, four, six, and eight weeks of age, and then monthly thereafter for life. Prescription dewormers for dogs typically are given orally, but some dewormer options can be applied to the skin.

“There are many safe and effective products that combine treatment and prevention of intestinal parasites with flea and heartworm prevention,” said Cox. To eliminate infection, your veterinarian can prescribe any one of a number of medications that come in tablets, edible powder, liquids, chewable pills, or topical preparations.

Side effects of the medications are mild, Cox noted, especially compared to the consequences of untreated infection, which include vomiting and profuse diarrhea.

Pets should be monitored with regular fecal examinations to be certain that the treatment is effective and to screen for other intestinal parasites, some of which require special de-wormers, Cox said.

What Kind of Worm Is It?

Roundworms, or Toxocara canis, are the most common worm found in dogs, Cox said. “Dogs can be infected from the environment through eggs, intermediate hosts (e.g., rodents or birds), or in utero,” she said.

In addition to roundworm, your dog could be affected by other intestinal worms, including hookworms and whipworms, which have similar symptoms, Marrinan said.

“Some of these parasites can stay dormant in the muscle as life-long infections from puppyhood,” he noted.

Tapeworms, another intestinal parasite, are less common than roundworms but can affect your dog. Typically, this infection is spread by fleas, said Marrinan.

Heartworms, as the name implies, settle in a dog’s heart, and in the lungs as well. This common parasite, which is particularly widespread in the nation’s southern states, occurs when a dog is bitten by a mosquito that is carrying the parasite, Marrinan said.

How to Prevent Worm Infection in Dogs

As with most health issues, prevention is preferable to cure, and for parasites, prevention comes relatively easily, Marrinan said. “Nearly all common parasites are controlled with monthly parasite preventives” given orally or topically, said Marrinan.

Even with attention to prevention and treatment, both Cox and Marrinan caution that dogs can become re-infected. For this reason, parasite prevention and monitoring should be considered a life-long issue for pets. 

This article was verified and edited for accuracy by Dr. Jennifer Coates, DVM


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