Most pet owners do not know their pets may carry worms capable of infecting people.1 Infected dogs contaminate their surroundings by passing eggs in feces. People can acquire roundworm and hookworm infections by coming into contact with an environment contaminated with eggs or larvae. That means it's important to clean up pet feces on a regular basis to remove potentially infectious eggs before they spread through the environment. Eggs in the environment can remain infectious for years.1 Children are more likely to become infected in part because they are more apt to play in contaminated areas or put dirty objects in their mouths. Almost 73% of pediatricians in the US reported cases of children with parasitic infection.2
Roundworms are commonly diagnosed in puppies,3and may infect 90% of puppies under three months of age.4 However, infection can occur in dogs of all ages. In a study roundworm eggs were found in 15% of all dogs.5
Once inside a dog's body, ingested roundworm eggs hatch and the larvae then migrate to the intestine and become adults. There, they feed, depriving the dog of vital nutrients and, in some cases, block the intestine entirely. Female roundworms can lay more than 100,000 eggs per day.6 Clinical signs can include diarrhea, weight loss and swollen abdomens. Left untreated, roundworms pose a serious health risk, especially for young dogs and puppies.
The incidence of human infection with zoonotic intestinal parasites is significant. According to a 2008 study conducted by the Center for Disease Control, overall roundworm prevalence in humans is 13.9% in the United States.7 Roundworm infection can cause morbidity in humans, however many roundworm infections remain asymptomatic and therefore remain underdiagnosed and underappreciated.7 Once inside a human, roundworms may migrate to areas of the body other than the intestine. This may make the disease more severe depending on the migration path and destination of the roundworms. When they migrate to the eye, they can impair vision or cause permanent blindness. These "wandering roundworms" can also damage the liver, heart and lungs in humans.
Hookworms are dangerous intestinal parasites that infect dogs. All areas of the United States have dogs infected with hookworms.5 In a nationwide study, hookworm eggs were found in 19.2% of all dogs. Prevalence varies from region to region.5
Hookworms present a severe health risk because of their unique feeding habit. They repeatedly remove a small amount of the intestinal lining, leaving bloody holes in their wake. This grazing results in blood loss and inflammation. Severe infection may lead to anemia, debilitation and even death.1 Young puppies are especially susceptible.
Hookworms are unique in their ability to penetrate human skin. When people come into contact with contaminated soil, infective larvae can pass through a person's skin and begin a prolonged migration under the skin, causing a painful, itchy rash. Some species of hookworms can penetrate deeper tissues. In rare cases, hookworm larvae may migrate to the intestine, causing an inflammatory response.8
As the saying goes, "Prevention is worth a pound of cure." Talk to your vet about intestinal parasites. He or she will recommend diagnosis and treatment appropriate to your dog.
1. Guidelines for Veterinarians: Prevention of Zoonotic Transmission of Ascarids and Hookworms of Dogs and Cats. Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, in cooperation with the American Association of Veterinary Parasitologists. Document available at www.cdc.gov/ncidod/diseases/roundworm/roundworm.htm. Accessed November 8, 2010.
2. Thomblison P. Pets, worms and little people. Contemporary Pediatrics. September 2003.
3. CAPC Recommendations. http://www.capcvet.org/recommendations/ascarids.html. Accessed October 13, 2010.
4. Schantz PM. Zoonotic ascarids and hookworms: the role for veterinarians in preventing human disease. In: Emerging vector-Borne and Zoonotic Disease, The Compendium Suppl 2002;24(1):47-52
5. Blagburn BL, Lindsay DS, Vaughan JL, et al. Prevalence of canine parasites based on fecal flotation. Comp Cont Ed 1996;18(5):483-509.
6. Lloyd S, Toxocarosis In: Palmer SR, Soulsby EJL, Simpson DIH, eds. Zoonosis. New York: Oxford University Press, 1998;842.
7. Won KY, Kruszon-Moran D, Schantz PM and Jones JL. National Seroprevalence and Risk Factors for Zoonotic Toxocara spp. Infection. Am J Trop Med Hyg 2008; 79(4):552-557.
8. Prociv P. Zoonotic Hookworm Infections. In: Palmer SR, Soulsby EJL, Simpson DIH, eds. Zoonoses. Oxford, Oxford University Press, 1998:805.