I’ve been playing phone tag with a friend recently. I guess it’s not too surprising considering that we’re all especially busy this time of year and she has a newborn (and four older children) in the house. I am hoping we get in touch with each other soon, though. She wants advice about coming up with a deworming protocol for her puppy and cats. She’s worried (and so am I) about the possibility that her pets could pass parasites on to her kids.


My two biggest concerns are hookworms (Ancylostoma spp.) and roundworms (Toxocara spp.). Here’s what the Centers for Disease control has to say about the zoonotic potential (the ability of animal diseases to spread to people) of these two parasites.



Puppies and kittens are especially likely to have hookworm infections. Animals that are infected pass hookworm eggs in their stools. The eggs can hatch into larvae, and both eggs and larvae may be found in dirt where animals have been. People may become infected while walking barefoot or when exposed skin comes in contact with contaminated soil or sand. The larvae in the contaminated soil or sand will burrow into the skin and cause the skin to become irritated in that area. For example, this can happen if a child is walking barefoot or playing in an area where dogs or cats have been (especially puppies or kittens).

Most animal hookworm infections result in a skin condition called cutaneous larva migrans. People are infected when animal hookworm larvae penetrate the skin, causing a local reaction that is red and itchy. Raised, red tracks appear in the skin where the larvae have been and these tracks may move in the skin day to day, following the larvae’s movements. The symptoms of itching and pain can last several weeks before the larvae die and the reaction to the larvae resolves. In rare cases, certain types of animal hookworm may infect the intestine and cause abdominal pain, discomfort, and diarrhea.


The most common Toxocara parasite of concern to humans is T. canis, which puppies usually contract from the mother before birth or from her milk. The larvae mature rapidly in the puppy’s intestine; when the pup is 3 or 4 weeks old, they begin to produce large numbers of eggs that contaminate the environment through the animal’s stool. [People] can become infected after accidentally ingesting (swallowing) infective Toxocara eggs in soil or other contaminated surfaces. There are two major forms of toxocariasis:

  • Ocular toxocariasis: Toxocara infections can cause ocular toxocariasis, an eye disease that can cause blindness. Ocular toxocariasis occurs when a microscopic worm enters the eye; it may cause inflammation and formation of a scar on the retina.
  • Visceral toxocariasis: Heavier, or repeated Toxocara infections, while rare, can cause visceral toxocariasis, a disease that causes abnormalities in the body’s organs or central nervous system. Symptoms of visceral toxocariasis, which are caused by the movement of the worms through the body, include fever, coughing, asthma, or pneumonia.


The best way to protect people from hookworms and roundworms is for all of us to pick up pet feces immediately when in a public environment and on a daily basis in our own yards, and to follow a veterinarian’s recommendation regarding fecal examinations and deworming. Hopefully I’ll get a chance to talk to my friend about this soon.


Dr. Jennifer Coates


Today's Fully Vetted was originally published in December 2012.


Healthy Pets Healthy People. National Center for Infectious Diseases. Centers for Disease Control. Accessed 12/17/2012


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