Roundworms are the most common worm infestation in dogs, especially young puppies. Their eggs are found in the soil -- thanks to the feces of infected dogs -- where they can survive for years. Puppies can also get the eggs through their mother's milk or even passed through the placenta while still in utero. Adults may carry them without any symptoms. Infected puppies however, may vomit, have diarrhea and lose weight. Sometimes they have a pot belly if there's a large infestation, fail to thrive or have a dull coat.
Roundworms have a strange life cycle. After a dog swallows the eggs, the eggs hatch into larvae. The larvae ride through the bloodstream to the lungs and from there up the windpipe, where they're swallowed again, return to the intestine, and finally become mature adult worms. These adult worms can be seen sometimes in the stool as long wriggling spaghetti strands. As with other types of worms, treatment consists of a deworming pill that kills the adults. Regular fecal exams by your vet should detect them. Again, practicing good dog sanitation is the best way to prevent an infestation.
Hookworms are similar to roundworms in a lot of ways: they usually affect puppies (although adult dogs can have them, too), and they can be passed in the mother's milk. Hookworm larvae, however can even burrow through the skin. And once in the dog's small intestine, they hook onto the intestinal wall, absorbing tissue and blood. One of the classic signs of hookworm infestation is dark, tarry, or bloody stool. In serious cases of hookworm disease, dogs suffer severe anemia and can die. Hookworms can also cause skin disease and infections in humans.
Like most other intestinal worms, hookworms are diagnosed by examining a stool sample under a microscope. If your vet finds hookworm eggs, he or she will probably prescribe medication to kill the adult worms. Typically this is one of the same deworming pills that kill other worms such as roundworms. The best prevention for hookworm is -- once again -- being diligent in picking up after your dog. The longer an infected dog's stool sits, the more likely it is that any hookworm eggs will hatch out into larvae and find their way under your dog's skin.
Worms are some of the nastiest parasites that can infect your dog. The good news is that they're all easily preventable if you follow a few simple rules: be careful about what your dog consumes, clean up after him well, take him in for regular exams, and keep him on medications provided by your vet to prevent the worms (including their hosts, such as fleas) from getting to him in the first place. Follow these and hopefully your dog will remain worm-free for life.