Roundworms are long, spaghettilike parasites who live in your dog’s intestine. They are common in puppies. In fact, pups can get them from their mothers before birth. All puppies should be wormed as a routine precautionary measure to ensure roundworms and others are eliminated, since the worms are not always obvious. It typically takes multiple wormings to get rid of them all, as wormer kills only adult roundworms living in the intestines.
Adult dogs often don’t show any signs of the presence of roundworms, since the worms in adult dogs are typically dormant; they can become active only if your dog becomes pregnant or ill, or is otherwise under stress. Puppies with roundworm infestations have pronounced potbellies and they may not grow well as the worms rob him of the nutrients in his food. Your pup may pass roundworms in his stool; you may find one or more of these pests if your puppy vomits. Too many roundworms can eventually block his intestine and kill him.