Gastrointestinal worms are common parasites in dogs and cats. Some of the worms can be transmitted to people and cause serious problems. Puppies, kittens, pregnant and lactating females and hunting dogs are a high risk group. Most puppies and kittens are often infested with worms and are cute, playful and irresistible. That increases the risk of contracting worms, especially among children, who spend hours playing, kissing and eating together with the pets. This article concentrates on human diseases caused by animal worms.

Round worms

The most important roundworm known to affects people is Toxocara canis, which is the most common worm in dogs (almost all puppies are infested). Studies show that more than 15,000,000 people in the United States are infected with the larvae of Toxocara from dogs and cats. 10,000 children are affected annually , 750 of whom lose their vision.

A study conducted by ophthalmologists reported that migrating Toxocara larvae caused 37% of the cases of retinal disease in children. Toxocara eggs are shed in the feces and contaminate the anal area and the environment, where they remain dangerous for years.

People contract the parasite by ingestion. Contaminated hands, close contact with contaminated pets and eating while playing with the pet are common methods of delivery. The eggs hatch in the intestine and the larvae invade the body, migrating through organs. They eventually end up in different sites (liver, lungs, heart, eyes, brain and more), where they can remain encapsulated for years.

Humans can develop two disease entities:

1. Visceral Larva Migrans- Multiple organ signs of variable severity, related to inflammatory response to the migrating larvae. Fever, pain or respiratory signs can be present.

2. Ocular Larva Migrans- Eye disease and vision problems with no systemic signs. Both diseases are more common in children.



Hookworms are common in dogs and less in cats. Puppies and hunting dogs are more often affected. Humans get infected by contact with contaminated dogs or environment. The worm penetrates wet skin and migrate within the skin or deeper. Ingestion is also possible.

Hookworms cause two disease entities in humans:

 1. Cutaneous Larva Migrans- A self limiting skin irritation.

2. Eosinophilic enteritis- Inflammatory bowel disease.



The most important zoonotic tapeworm is Echinococcus, which Luckily is not widespread. People contract the infected eggs by ingestion. Contact with infested dog's feces, contaminated hair or environment are the delivery methods. The eggs hatch in the intestine and the larva migrate through organs, where it forms large cysts (Hydatide) and cause severe damage. The disease is called Echinococcosis or hydatide disease and it is potentially fatal.

Dipylidium caninum, the most common tapeworm in dogs and cats can cause less severe intestinal disease in people. People get infested by accidentally ingesting flea larvae and not by contact with affected pets. People can develop digestive signs, such as vomiting or diarrhea.


Prevention Strict hygiene and supervision of children should be exercised. Avoid soil ingestion, eating while playing with the dog, and oral contact with the dog or unwashed hands. Ensure frequent hand wash, cleanliness of the dog and prompt removal of feces after elimination. Multiple deworming of every puppy and kitten by the veterinarian is needed to remove the worms. Have at least one fecal exam every year. Many of the heartworm preventatives also eliminate intestinal parasites and are highly recommended. Rural and hunting dogs as well as females during pregnancy and lactation should be treated more frequently.

More information from the CDC http://www.cdc.gov/ncidod/dpd/parasites/toxocara/default.htm

Read more about pets and parasites

Copyright © 2004 - 2013
Yuval Nir
Naperville University Commons Animal Clinic- The-vet.net
1827 Wehrli rd
Naperville , IL , 60565
(630) 544-3333
Veterinarians, Animal hospital