Roundworms in Dogs

Infection with intestinal parasitic roundworms (called ascarids) is very common in dogs. Roundworm eggs are ingested from the soil or feces. The eggs hatch and adults feed off of nutrients in the small intestines, causing digestive issues and damaging the intestinal wall. Since infection is very common in puppies, the breeder or veterinarian will normally deworm puppies as a rule. Since an infected pet can pass millions of eggs each day and the worms can also cause disease in humans, it is important to deworm pets and wash hands regularly. Dogs become infected with ascarids via ingestion of larvated eggs from a contaminated environment, such as feces, and ingestion of other vertebrate hosts that have consumed larvated eggs and thus have larvae in their tissues. All dogs should be screened for intestinal parasites, including parasitic roundworms, at least four times in the first year of life and at least two times per year in adults depending on patient health and lifestyle factors.

Roundworms live in the small intestines as adults. In the larval stage, they can reside in other organs including the lungs. Symptoms may not be observed at all with roundworm infection, however, the following gastrointestinal (GI) tract and respiratory symptoms may be observed:

• Abdominal swelling
• Diarrhea
• Vomiting
• Weight loss
• Coughing
• Lethargy
• Adult worms in stool and/or vomit (adult worms are a white or tan color and can be 3-7 inches long. They have the appearance of “spaghetti.”)

Types

There are two common types of roundworm that infect dogs. Each can be carried in rodents and has a unique lifecycle.

• Toxocara canis – This ascarid infects dogs through 4 routes: Pet eggs on feces or vomit, pet eats a small rodent carrying larvae, pup infected with larvae from mother through the placenta, or pup infected with larvae from mother through nursing. After the dog eats the eggs, the larvae hatch and enter the bloodstream. They then enter the lungs, are coughed up and swallowed, and develop into adults in the small intestine where they feed and lay more eggs.
• Toxascaris leonine– This ascarid infects dogs through 2 routes: The pet eats eggs on feces or vomit or eats a small rodent carrying larvae. After the dog eats the eggs, the larvae hatch and develop into adults in the small intestine where they feed and lay more eggs.

Dogs are able to become infected with roundworms through the following routes:

• Eating feces from an infected animal
• Eating an infected small rodent
• Eating vomit from an infected animal
• Pup infected through the infected mother in utero.
• Pup infected through nursing from infected mother.

If you have noted symptoms of roundworm infection or have seen adult worms in your pet’s stool or vomit, you will want to take your pet to the vet for treatment. If possible, bring a sample of stool less than 24 hours old for the vet to run a fecal analysis.

Physical examination will usually note a swollen abdomen often seen with roundworm infection along with reports of weight loss, inadequate weight gain in puppies or coughing. If you are unable to supply a fecal sample from home, your vet can take a sample at the clinic.

The diagnosis of roundworm infection is done through a fecal floatation. In this test, a sample of feces from your pet is mixed with a liquid solution that causes the worm eggs to float to the top of the mixture. The top layer is placed on a slide and viewed under the microscope. Roundworm eggs are easily identified. A sample of feces or vomit containing adult worms is also diagnostic.

Roundworm infection is common and treatment is fairly straightforward. A variety of oral deworming drugs are available to kill the adult roundworm, including pyrantel, milbemycin, fenbenzadole and moxidectin.

Deworming medication does not kill the eggs of the roundworm. Depending on the medication’s length of action in the body, your pet may need to be treated one to three times to get rid of the adults and the newly hatched worms. In the case of the three-dose regimen, the pet will receive one initial dose, then two more doses 7-10 days apart (allowing time for existing eggs to hatch and become susceptible to the medication).

Puppies can be dewormed as early as 2 weeks of age, depending on the medication. It is important to clearly understand the instructions for the dewormer if you are planning to administer it yourself. Each medication varies in the age, dosage and treatment schedule. Using a dewormer in an animal too young for that medication can be life threatening.

Follow the veterinarians instructions carefully, being sure to administer follow-up doses of dewormer on the correct schedule. For animals who are being treated for roundworms, a repeat fecal analysis is recommended at 2 and 4 weeks to ensure that no roundworm infection is remaining.

One adult roundworm can produce up to 80,000 eggs daily, so exposure is common. Puppies should have fecal tests done every 3-6 months. Adult dogs are recommended to have their feces tested for intestinal parasites every 6-12 months.

Prevention of roundworm infection can be helped by deworming puppies early, deworming any new pets, preventing pets from eating rodents, keeping bedding and dishes clean, giving a monthly roundworm prevention (included in some heartworm treatments), and running fecal tests regularly.

Human roundworm infection is rare but possible. Direct contact with animals doesn’t normally cause infection since eggs have to be ingested after resting outside of animals for 14 days. Infection in humans will normally come from ingesting soil or feces from infected animals. Washing hands regularly is the best preventative of human infection.