Canine Roundworm Infection

Roundworms are the intestinal parasite of dogs. Toxocara canis and Toxascaris leonine are most often affected by dogs. Roundworms are thin white spaghetti-like worms about 18 cm or 7 inches in length. They are certainly visible to the human eye as adults, but the eggs or larvae may not be as easily detectable. Roundworm larvae are most prevalent during pregnancy, which is why it's said that 95% of all puppies are born with this worm. This is also why puppies are automatically treated and dewormed as soon as they're born. The worm parasites are often transmitted to the puppy through the mother's placenta before birth and after birth by the mother's milk. Transmission also occurs from contaminated areas such as the grounds from a dog park.

Roundworm Lifecycle

The roundworm like many other worms has several complex and environment-dependant stages of development. For Toxocara eggs, the most complex development cycle of the two, begin by being passed in the host animals feces where it has a month long growth cycle. It's at this second stage where it's ready to infect its next host and can live at this stage for months, sometimes years.

Incredibly, the roundworm can only develop to its third stage from a canine, thus another animal may pick up these second stage larvae which hatch in its intestinal tract, leave and lay waiting in a new patch of feces for a canine to pick it up.

Once consumed by a dog, the parasite then migrates to its lungs to complete its third stage of development. They navigate through the airways and up to the throat causing the dog to cough. Sometimes this causes pneumonia if infection is bad enough. Once coughed up, the dog then swallows the young worm where it burrows its way back to the intestinal tract where it continues to mature to their last stage of growth. Once sexually mature, roundworms immediately begin to mate. This entire lifecycle can take as little as 4 to 5 weeks with new larvae already in the host's intestines.

If the canine is pregnant, the larvae will not follow the path to the lungs to be coughed up, but instead the hormones in the female dog will redirect the larvae to move through the placenta infecting the unborn puppies or through the mammary glands to infecting the nursing puppies.


Puppies affected by roundworm often vomit them up putting these worms up for display. Coughing, developing a potbelly, diarrhea, weakness, emaciation (extreme weight loss) and pneumonia are all common signs and can be severe enough to cause death if not treated soon enough.

prevention and tretment

Prevention and treatment are nearly one in the same. Regular deworming is a popular choice as the same medication the treats or kills the worms in its various stages is also nicely suited to ensure that when your canine companion gets contaminated, the parasites are killed on the spot. Preventing roundworm is also done through the use of plain old common sense. Maintain hygiene in and around your home by disposing of feces, washing hands regularly and keep your dog clean. Don't take your dog to unsanitary dog parks and make sure any meat your dog eats is well cooked. Keep kennels clean and dry. Using bleach when mopping will kill the larvae.

Treatment is highly important as roundworm can also affect humans. Annual deworming and checkups are recommended for adult dogs. Puppies usually have already been treated for worms by the breeder or handler before finding their new homes. It is smart to obtain the deworming history before accepting a new pet.


Dogs believed to have hereditary renal disease should not be bred. Owners of aging dogs should watch for signs of renal disease in their pets and seek veterinary care early on.

Pyrantel pamoate dewormer by VEDCO is a highly effective wormer used for the removal of hookworms and roundworms in dogs and puppies. The concentration is 50 mg pyrantel pamoate per mL. The dosage is 3 ml per 50 pounds of body weight. Each bottle contains 473 mL (1 Pint).
Nemex - 2 by Pfizer is a highly effective wormer used for the removal of roundworms and hookworms in dogs and puppies. The dosage is one teaspoon (5 mL) for each 10 lb of body weight. Each bottle contains 2 fluid ounces (60 mL). The active ingredient is pyrantel pamoate.
There are two species of roundworm 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 is not necessary to determine which species is present.
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