Preventing Zoonotic Disease: Roundworms, Hookworms and Tapeworms
As the number of pets in the United States increases, so does the likelihood that both pets and pet owners will be exposed to parasites. Recent national surveys indicate that the prevalence of major parasites in dogs and cats remains surprisingly high. Some of these parasites can also infect people; these parasites are considered zoonotic. Understanding parasites such as roundworms, hookworms, and tapeworms and how to control them is essential in preventing zoonotic diseases.
Roundworms of dogs and cats are large worms that live as adults in the small intestine. Larvae usually migrate through the liver and lungs of their host before they mature in the small intestine; this process generally takes between 2 and 5 weeks. Adult roundworms can produce up to 85,000 eggs per day. This rate of egg production, combined with the long survival rate of the eggs, can increase the risk of exposure and infection for both pets and people.
These roundworms are important not only because they cause diarrhea, lethargy, and weight loss in dogs, but also because the larvae can cause what is called larva migrans in people. When people ingest roundworm eggs, the migration of larvae and resulting damage to internal organs is referred to as visceral larva migrans (VLM). VLM occurs most often in children younger than 3 years of age. In children 3 to 13 years of age, the larvae often migrate to the eye. Inflammation of the retina is the hallmark of this syndrome known as ocular larva migrans (OLM). OLM can result in retinal detachment, loss of vision, and blindness.
A recent article from the CDC indicates that 14% of the U.S. population has been infected with roundworms contracted from dogs and cats.
Canine and feline hookworms are small whitish or reddish-brown worms that are hooked at one end. As adults, they also live in the small intestine of dog and cats. Hookworm larvae either enter the pet through the skin or are swallowed. Those that penetrate the skin migrate through the lungs before ending up in the small intestine. Hookworms can also be transmitted during pregnancy or lactation.
Hookworms can cause skin, lung, and intestinal disease in dogs and cats, as well as acute, life-threatening disease in young dogs. Adult hookworms produce up to 20,000 eggs per day, which can result in substantial numbers of eggs and larvae in the environment in rather short periods of time.
The larvae of some hookworms can also penetrate human skin. Dermal infections appear as itchy, reddish, coiling lesions. This condition is referred to as cutaneous larva migrans or “creeping eruption.” Rarely, hookworm adults may also inhabit the intestines of people. Recurrent abdominal pain is a common symptom.
Tapeworms are thin, segmented parasites that can grow up to several feet long. Current surveys suggest that intestinal tapeworms are underdiagnosed in pets. This may be partly because tapeworm infections do not usually cause detectable disease in dogs and cats.
Tapeworms are transmitted by consumption of fleas, usually during a pet’s self-grooming. Tapeworm segments are long and thin and resemble grains of rice. Human infections occur when fleas are inadvertently swallowed, usually by small children. Although tapeworms do not usually cause clinical signs of disease, infections in children are a cause of alarm among parents and caregivers when tapeworm segments are passed in feces or found in soiled diapers. Human infections are best prevented by controlling tapeworms and fleas in dogs and cats.
HOW CAN YOU HELP PREVENT THESE DISEASES?
Acquiring and maintaining a healthy pet and practicing good hygiene—and encouraging children to do the same—can virtually eliminate any risk of acquiring parasites from your pet:
- Purchase or adopt pets from reputable breeders and shelters that maintain only healthy animals.
- Take your pet to your veterinarian at least twice a year for vaccinations, fecal testing, and wellness examinations.
- Ask your veterinarian about the use of parasite control products, particularly those used primarily for heartworm prevention or flea and tick control that also possess activity against other internal parasites.
- Consult with your veterinarian regarding all cases of diarrhea in your dog or cat.
- Feed pets only a commercially prepared, complete diet, and prevent them from hunting and consuming prey animals.
- Support fecal removal and leash policies in pet exercise areas and public places.