Worms and Internal Parasites


Parasites are organisms that live in or on your dog, causing harm. Minimizing parasites is an important part of keeping your pet healthy. Some pet parasites can cause problems for people too, so keeping them out of your home is also good for you and your family.

The most common internal parasites of dogs live in the gastrointestinal tract. You may see some of these organisms in your pets feces, but a fecal analysis by your veterinarian is more reliable. Some parasites live in the bloodstream or other parts of the body. Blood tests may be required to detect these. Most internal parasites can be treated with medication available from your veterinarian.


Almost all puppies acquire roundworms from their mothers. The worms look like curly pieces of spaghetti and may be several inches long. Heavy infestation with roundworms may cause a dull hair coat and pot-bellied appearance. Roundworms can also cause disease in children, so all puppies should be routinely tested and treated. The treatment is a simple oral medication, but it must be repeated two or more times. It is important to follow label directions exactly. You can help prevent the spread of roundworms by cleaning up animal feces as soon as possible, especially in your yard.


Tapeworms are one type of worm you may very likely see in your pets stool. The worms are long and flat (like a narrow piece of tape), but you will rarely see the entire worm. Small segments, resembling grains of rice or sesame seeds, break off periodically and appear in the feces or on the hair around your pets anus. Tapeworms are spread when your pet swallows an infected flea while grooming himself, or when he eats an infected animal, such as a mouse. Tapeworms may cause anal irritation, and some types can cause problems in children. You can prevent your pet from being exposed to tapeworms by controlling fleas and discouraging hunting. Your dog can be treated for tapeworms with an oral or injectable medication.


Hookworms look similar to roundworms, but are smaller. Hookworms live in the small intestine where they feed on blood. They can cause severe anemia and even death in puppies. Hookworm larvae live in the soil, especially in warm, humid areas. They can cause skin infections in humans. Hookworms can be treated with an oral medication. Picking up animal feces immediately can also help with prevention.


Whipworms get their name because part of the worm is short and thick, like the handle of a whip, while the rest is long and slender, like the lash. They are common in dogs. Whipworms can cause diarrhea and colitis. Treatment and prevention are similar to that for roundworms and hookworms.


Protozoan parasites of the intestine include Giardia and Coccidia. All are microscopic. Giardia and Coccidia often cause diarrhea in puppies. Giardia can be spread to humans as well. Oral medications are available to treat for these organisms.


Heartworms are worms that look very similar to roundworms, but live in the heart. Their microscopic larvae circulate in the blood and are spread by mosquitoes. Heartworms are common in dogs. Without treatment, heartworm infection causes damage to the heart and lungs and is often fatal. Therefore, prevention is crucial. A variety of convenient preventive medications are available from your veterinarian. Routine blood tests are recommended annually or more often if preventive treatment has been interrupted. Once infected, dogs can be successfully treated for heartworms, but the treatment is much more involved than that for intestinal worms.