Animal Resource Library » Health & Safety » Zoonoses & Parasitic Diseases (i.e., Worms)

Zoonoses & Parasitic Diseases (i.e., Worms)

Zoonotic diseases are those diseases and infections which are naturally transmitted between animals and man. This means that zoonotic parasites can affect both pets and people. Protecting pets from zoonotic parasites greatly reduces the risk to humans. Prevention and routine screening from your veterinarian is important to protect you and your family. This should include a yearly fecal exam of all pets in the household.

There are quite a few zoonotic diseases, but this segment’s focus will be on parasites that are shed in the stool of your pets. Dogs and cats are victims of several internal parasites frequently referred to as worms. The most common are roundworms, hookworms and tapeworms. These worms, which infect and reinfect your pet, can also infect humans, so treatment and eradication of the worms in the environment are important.

Adult roundworms are fairly long, white, and tubular in shape and resemble half-lengths of spaghetti noodles. These worms swim inside the small intestine and feed on the animals digested food. Because roundworms can grow to be 8 to 12 centimeters long, an infection of multiple adults is capable of causing inflammation and distention of the bowel loops.

Early diagnosis of the presence and species of intestinal parasite is important because not all worms respond to the same treatment. Therefore, stool samples should be taken to your veterinarian for microscopic examination. This is called a fecal exam. Many veterinarians include the stool check as part of the annual health examination.

Almost all puppies are born already infected with roundworms, which are the most common intestinal parasite of the dog. Toxocara canis, a species of roundworms, is capable of migrating across the infected mother dog’s placenta and into the unborn puppies. Ingesting worm eggs from contaminated soil infects dogs. Kittens are affected more commonly than adult cats. These worms can be passed on to kittens in the milk they nurse from their infected mother. Cats may also get them by eating small animals that harbor the parasite. In addition, a cat may become infected by licking its paw after walking on soil contaminated with infectious roundworm eggs.

Roundworms can lead to a host of medical problems including a pot bellied appearance, stunted growth, weight loss, dry hair, general poor appearance, vomiting and diarrhea. Severe infestation can lead to dehydration and even intestinal blockage.

Prevention is the key. Puppies can be de-wormed as early as two to three weeks of age and should be de-wormed every two weeks until they are three months of age. Nursing females should be treated concurrently with the pups. Kittens can be de-wormed starting at six weeks of age and repeated every two weeks until they are 12 weeks of age. All new pets should have, in addition to a physical exam by your vet, a fecal performed to check for worms. Adult pets should be checked annually.

Fortunately, most human infections with roundworms are so mild they go unnoticed and apparently produce no permanent damage. However, they have the potential to produce severe disease. Young children who play in uncovered sandboxes, litter boxes or dirt that has been contaminated with animal feces from infected puppies or kittens are especially at risk for contracting the disease. Direct contact with infected animals does not produce infection, as the eggs require a three to four week extrinsic incubation period to become infective. Thereafter, eggs in soil remain infective for months to years. Once inside humans, the hatched larvae are unable to mature and continue to migrate through the tissues for up to 6 months. Eventually they lodge in various organs, particularly the lungs and liver and less often the brain, eyes, and other tissues. The damage is aggravated by the strong allergic inflammatory reaction the larvae provoke in human tissue. Symptoms in humans include fever, cough, and wheezing.

Therefore, keeping young children away from areas contaminated with feces and encouraging them to wash their hands after playing and before eating is important in preventing the disease. All sandboxes should be covered when not in use.

These are small, thin worms that fasten to the wall of the small intestine and suck blood. This parasite frequently infects puppies and kittens.

Dogs get hookworms if they come in contact with the larvae in contaminated soil. Puppies can contract hookworms in the uterus and also from ingesting contaminated milk while nursing.

A severe hookworm infestation can pose serious health problems and even death, from a severe anemia, in puppies and kittens. Other clinical signs of hookworms in dogs and cats are diarrhea, blood in the stool, weight loss and weakness.

Hookworms are considered a human health hazard since the infectious larvae can penetrate the skin and migrate locally. This is called cutaneous larval migrans. Clinical signs in humans are localized to the site of larval entry, particularly in the hands and feet. The lesions are usually red and very itchy. So anyone running barefoot in moist, sandy areas, or in their yard or park where the grass is wet can contract visceral larval migrans from hookworm larvae.

The adult tapeworm is made up of many small segments called proglotids, each about the size of a grain of white rice. Usually, single proglotid segments, which contain tapeworm eggs, break off the tail end of the tapeworm and are passed into the stool. These segments sometimes will remain visible on the pets rear after it has had a bowel movement. They may also crawl out of the anus when the dog is very relaxed or sleeping.

Tapeworms are a common intestinal parasite. There are two primary ways that dogs and cats can become infected with tapeworms. Pets can swallow a flea when they are chewing or licking themselves, and if that adult flea contains infectious tapeworm larvae, then the pet will become infected with tapeworms. Less commonly, dogs and cats can become infected when they eat a rodent, which can harbor a different species of the tapeworm.

Humans can become infected with tapeworms if they ingest the eggs from soil, hands or objects contaminated by dog or cat feces. Most cases involve young children eating dirt contaminated with animal feces.

To prevent human infection with pet-associated worms:

  • De-worm puppies and kittens early and repeat every two weeks until they are 12 weeks of age.
  • Mother dogs and cats should be treated at the same time as the puppies and kittens.
  • Keep young children away from contaminated areas and have them wash their hands after playing and before eating.
  • Have new pets checked right away by your veterinarian. Ask for a fecal exam.
  • Have all adult pets checked annually with yearly fecals.

Please note, articles in the Animal Resource Library are for reference only, and are not meant to diagnose or treat any medical or behavioral issues your pet may be experiencing.