As family members, dogs can transmit diseases to their human cohabitants. One class of disease that can be especially difficult to control due to the natural behavior of dogs is parasites. Dogs have no aversion to digging in the ground "bare pawed" or inspecting their own or others fecal deposits. This behavior makes them easy targets for parasites.
According to Ray M. Kaplan, DVM, puppies are in the high-risk category for roundworms. If they are well-cared for and have normal immune systems, puppies will develop an immunity to roundworms when they are 2 to 3 weeks old. If they are infected, drugs are available that quickly kill roundworms. Roundworm eggs are transmitted only by feces, so it is important to keep away from puppy excrement and to keep their fur clean to control contamination. It's important to keep puppies clean and to instruct children to keep their mouths off the dog and to wash their hands regularly. It is equally important to have pets dewormed regularly.
The Cornell University College of Veterinary Medicine reports that hookworm infection in humans is relatively rare because the hookworm's natural host is dogs. Hookworms can be ingested or the larvae can penetrate the skin or pass from mother to offspring through the uterus or mammary glands. The only way a hookworm can enter a human is by penetrating the skin. So human infection occurs through contact with an infected animal, by brushing up against a plant containing hookworm larvae or by touching contaminated soil with bare skin. Hookworms are easily killed in dogs and humans with drugs. Regular deworming prevents infection.
Tapeworm infection by a dog is extremely rare, according to the Cornell University College of Veterinary Medicine. In order for a human to be infected with a tapeworm from a dog, the person must ingest a flea from the infected dog that contains the larvae of the tapeworm. Even though this is rare, it is possible. Dogs become infected with tapeworms by ingesting cast-off worm segments from the feces or by the dog swallowing an infected flea. Fleas cause itching, and dogs will lick itching areas to alleviate the irritant. In the case of tapeworms, flea control and regular deworming are important.
According to the Cleveland Clinic, this parasite is most commonly found in tropical areas like the southern United States. The whipworm is a species of roundworm shaped like a whip. Whipworm eggs are passed by the feces. Dogs catch whipworms by ingesting contaminated soil, food or feces. Infection rates in humans are high, especially in children. Infection occurs by ingestion of eggs or worms in soil or on contaminated food. Like most worms, the whipworm responds to drugs and is easily killed. Even if left untreated, most infestations are not severe. The best prevention comes from regularly deworming pets and washing hands after contacting soil.
Cryptosporidium is a microscopic protozoan parasite. The Centers for Disease Control and Prevention warns that dogs infected with Cryptosporidium can pass it to humans through their feces. Cryptosporidium is very infectious. People who have compromised immune systems should be especially careful when contacting objects possibly contaminated with feces. There is no effective treatment for this parasite in humans. Dogs acquire Cryptosporidium the same way as humans, through contact and ingestion of fecal-contaminated food, objects or water. Incidence of infection in dogs is high, perhaps as much as 50 percent. Self-care such as washing of hands after contacting possible contaminants is the most important way of preventing infection.