<p>Worms in Dogs Roundworms Usually spread in feces or during pregnancy or nursing, the roundworm causes a serious infection in dogs and puppies. The roundworm eats the food of its host and may cause diarrhea and other symptoms. In puppies, roundworms can be fatal. Prescription and over- the-counter de-worming products for dogs are very effective. If people contract roundworms, their symptoms can be even more serious than those in dogs Hookworms</p><p>Living mainly in the small intestine, hookworms suck the blood of their hosts. Puppies can become infected from their mothers. Adult dogs can be infected through their skin or when cleaning themselves. Infection causes weakness and malnutrition and can lead to death in puppies. Two rounds of de-worming medication are usually effective, but a puppy may need other treatment, as well. Humans can also become infected with hookworms from unwashed vegetables or by walking barefoot on sand and soil. Heartworms Heartworms are spread to dogs through mosquito bites. Up to 14 inches long, a heartworm lives in the heart and the arteries that carry blood from the heart to the lungs. Heartworms affect how the heart functions and how blood clots and is likely to cause death if untreated. Monthly heartworm preventives are effective. If infected, your dog may cough, have trouble breathing, and experience other symptoms. Treatment may involve two or three injections of arsenic-based drugs, followed by at least a month of rest. Whipworms Whipworms live in the area where the small and large intestines meet. Here, they suck the blood of their hosts. Dogs can pick them up from contaminated soil or by grooming. Whipworms do not cause serious blood loss or other serious symptoms unless large numbers embed in the intestine. Some heartworm preventives are effective against whipworms, and an oral de-wormer is effective at eliminating whipworms.</p>