girl_and_dogRoundworms, also called ascarids, are the most common worms of dogs and cats. The adult worms are found in the intestine and live on gut content. They resemble spaghetti-in the appearance, being 2-3 mm thick and up to 20 cm long.

How Roundworms are Transmitted

Almost all puppies are already infected while still in uterus or acquire the infection immediately after birth, through their mother’s milk. In addition, roundworms can be acquired from the environment, by accidentally ingesting the infective eggs in contaminated soil or by eating infected rodents.

Understanding the Life Cycle of the Roundworm:

The Key to Elimination

Adult roundworms live in the small intestine of dogs, where they lay up to 80,000 eggs per day. These eggs are shed in the environment through the dog’s feces and, within a few weeks, an infective larva develops inside.

When a dog picks up the infective eggs, these hatches in its stomach and the larvae penetrate the stomach wall and start migrating to several organs before coming back to the intestine and develop into adult, egg-laying worms. Some larvae do not go back to the gut: they remain encysted in the various organs until a stimulus such as pregnancy, reactivates them and leads them to restart migrating and develop to adult worms in the intestine.


Roundworms are especially harmful to puppies, in which the migrating larvae can cause liver, lung and brain damage. The presence of the adult worms in the intestine leads to a gut inflammation, which affects digestion, development and growth. Common symptoms of heavy infections include vomiting, diarrhea, obstipation, colic, anemia, rachitic symptoms, poor growth and a “pot-bellied” appearance. A heavy accumulation of roundworms in a puppy can lead to death.

Treating Roundworm Infection

Since almost all puppies are already infected at birth, and are continuously reinfected through their mothers milk or through the environment, it is important to initiate the anthelmintic treatment in their very first weeks of life and to treat them frequently afterwards (e.g. fortnightly or monthly from 2 to 8 weeks of age, then monthly until they are 6 months old). Lady dogs should be treated concurrently. This will prevent puppies to develop the disease and to shed worm eggs through the feces, thus avoiding environmental contamination. Because of the extreme diffusion of roundworms, and the facility in getting the infection, adult dogs should also be treated regularly (e.g. 2-4 times per year). Many drugs are provided for treatment and prevention. Some of them are also effective against all other common dog worms thus ensuring a complete protection of your pet. Be sure to give to your pet the one that best satisfy his and your needs, in terms of ease of use, efficacy and safety (especially if very young pups are to be treated).

Information provided by Norvatis Animal Health.