Roundworms are the most common form of internal parasites and dogs rarely exhibit any symptoms of a problem other than the appearance of cylindrical shaped worms, which can be as long as four inches in the dog's stool. Puppies are in most danger when the roundworm is passed from mother before birth.
Hookworms can be found in dogs that live in warmer climates. They are transferred into the soil via contaminated stools. Symptoms include anemia, diarrhea and emaciation. Best way to prevent this type of worm is to pick up regularly after your dog. These worms are not visible to the eye. Diagnosis needs to be made by your veterinarian.
Whipworms live in the large intestine and are picked up from dogs ingesting contaminated soil. Again, diagnosis should be made from your veterinarian since the whipworm is difficult to detect. Keeping the dog's soil/play area clean will help prevent whipworms.
Heartworm is the most serious of the common internal parasites and can be found almost everywhere. Dogs that have been bitten by a mosquito infected with the heartworm larvae will develop worms 6 to 12 inches long. As these worms mature, they take over the dog's heart and can be deadly, as heart and liver function become affected. Symptoms may include coughing, tiring easily, difficulty breathing and weight loss in spite of a hearty appetite. Verification of heartworm is done via a blood test, which is strongly recommended ANNUALLY, in the spring. Because treatment in a positive - tested dog can be dangerous if not administered properly, if is strongly urged that only a veterinarian treat the dog.
A once - month medication is advised in the prevention of heartworm, usually in the distribution of a pill. These medications now even offer preventives to other internal parasites (ie the whip, round worm). How safe these preventive medications are is open to debate.