If your puppy has roundworms, don't panic. Caring for a puppy with roundworms consists primarily of deworming him with medications recommended by your veterinarian. While there are several ways in which a dog can contract roundworms, in puppies the worms usually arrive via the mother dog. The infected mother either passes on the roundworms while the puppies are in utero, or they pick up the worms while nursing or from her feces.
Two types of roundworms, or ascarids, affect puppies. The primary type, Toxocara canis, also can infect people. Another type, Toxascaris leonina also infects felines, so if cats share your household, they are at risk if not on a current deworming program. Puppies more often suffer from T. canis, while T. leonina more often infects adult dogs. If your puppy contracts roundworm larvae through the placenta, the larvae stays in his lungs and liver until he's born. Once the puppy has entered the world, the larvae move from his lungs to his airways, eventually heading to his small intestine.
Puppies born with roundworms generally don't gain weight and exhibit dull, lifeless coats. Although they don't gain weight as well as uninfected puppies, they often appear to have a potbelly, which is full of worms. Newborn puppies born with a severe infestation often die within a few days. If an older puppy -- 16 weeks and older -- isn't treated for roundworms, he might vomit up a mass of live, wiggly specimens.
Since roundworms in puppies are so common, your veterinarian routinely will deworm your puppy around the age of 2 weeks. If the mother dog was dewormed before she was bred and again before the puppies were born, there's a good chance her puppies won't have roundworms. However, if a puppy has an active case of roundworms, he'll need a few doses of dewormer spaced out every few weeks. The dewormer kills adult roundworms but not the larvae, so the additional doses kill off the newly matured worms. When your vet prescribes monthly heartworm preventive medication for your puppy, that chewable tablet or pill also eradicates roundworms. If the mother dog didn't receive dewormers prior to or during the pregnancy, it's important that she is treated along with her litter.
To ensure that your puppy's roundworms are gone, take a fecal sample to the vet for testing every few months for the dog's first year. After that, even if the dog is on a heartworm preventive, he needs at least one fecal sample testing annually. If testing reveals that roundworms are still present, your vet must perform additional dewormings. In puppies not yet on heartworm preventive medication -- which usually contains ivermectin -- that might mean using a different type of dewormer. For example, piperazine might not be as effective as certain other dewormers, such as pyrantel pamoate and fenbendazole.