What Kind of Worms Can Be Transmitted From Dogs to People?

by Catherine Troiano
Young children are especially at risk for contracting zoonotic parasites.

Young children are especially at risk for contracting zoonotic parasites.

Ryan McVay/Digital Vision/Getty Images

Intestinal parasites are common findings in dogs and puppies. Some intestinal parasites are zoonotic, meaning that they are transmissible to humans. This is particularly concerning in families with young children who tend to handle things indiscriminately and then place their fingers into their mouths. Whipworms and Isospora, or Coccidia, are two common intestinal parasites that are not zoonotic, but there are others that can affect you and your family. Fortunately, intestinal parasites in dogs are easy to treat, and steps can be taken to prevent future infections.

The Common Roundworm

Toxocara canis, also known as roundworms, are the most commonly found intestinal parasites in dogs. There are four possible routes of transmission to dogs. One route is ingestion of roundworm eggs from the soil. Dogs who hunt and consume infected prey can contract the parasites. Pregnant dogs who are infected can pass roundworms to their developing fetuses. Mother dogs who are nursing can pass the roundworm infection to their puppies through the milk. Performing a fecal flotation analysis of the dog’s stool will confirm the presence of roundworm eggs. When a human contracts roundworms, the parasite attempts to live out its life cycle. Since its usual host is a dog, the roundworm gets lost as migrates through the human body, and it typically ends up in the eye. This condition is called visceral larva migrans. Permanent partial blindness results if the roundworm dies within the human eye.

The Blood-Sucking Hookworm

Ancylostoma caninum, or hookworms, are bloodsucking intestinal parasites. Female hookworms shed their eggs, which are passed through the dog’s feces into the environment. Another host ingests the larvae, and then the larvae migrate through the body until they take up residence in the host’s gastrointestinal tract to mature. Rodents and birds also can serve as hosts. If a dog consumes one of these infected animals, he will contract the hookworm infection. Larvae in the soil can infect a host by seeping through the skin and entering the bloodstream. Pregnant dogs can pass the hookworms to their unborn puppies, and nursing mothers can infect their puppies with their contaminated milk. A fecal flotation analysis on the dog’s stool will confirm the presence of hookworm eggs. Hookworms can infect humans by penetrating the skin, resulting in an intensely itchy condition called cutaneous larva migrans. Humans also can contract hookworms through ingestion.

The Giardia Protozoan

Giardia is a protozoan intestinal parasite that is contracted through ingestion. The most common sources of giardia are stagnant and contaminated water. Once consumed, the giardia infection results in diarrhea and weight loss. Cysts are shed in the diarrhea to contaminate the environment and infect a new host. A giardia infection compromises the intestinal linings ability to absorb vitamins and nutrients. Microscopic examination of a direct fecal smear or of a sample that has been stained with iodine can reveal the presence of giardia. Another diagnostic method is a fecal flotation test performed with zinc sulfate as the floating medium used to reveal giardia cysts. A giardia ELISA test kit is now available as an easy method to diagnose giardia quickly. The giardia type that typically infects humans is different from that which infects dogs, but contact with the feces from an infected pet or human and subsequent ingestion of the parasite results in humans and animals alike contracting the giardia infection. Seek treatment is you think you or your dog has contracted giardia.

Prevention Future Infection

While your dog or puppy is being treated for intestinal parasites, be diligent that everyone in the household, particularly children, pregnant women, the elderly and those with compromised immune systems, practice frequent and thorough hand-washing hygiene. Avoid allowing the dog to lick people’s faces. Ask your veterinarian to recommend a shampoo to clean fecal residue from your dog’s coat. While wearing gloves, clean up all fecal material from the yard when your dog eliminates. If your puppy has an accident in the home, scrub surfaces with a mixture of water and bleach, if possible. Once your dog has been treated, ask your veterinarian about a monthly heartworm preventative that also prevents some of the common intestinal parasites. If you dog is sick with any of these parasites, always seek medical attention.

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