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Toxocariasis (Round Worm Infection)Toxocara

Toxocariasis is an infection caused by the intestinal roundworms of dogs (Toxocara canis) and, to a lesser extent, of cats (T. cati).  Infected dogs and cats shed the eggs in their feces.  The eggs then need to mature in the environment for two to four weeks before they become infective to humans or other animals.  Once the eggs are in the environment, they can survive for years in moist, shaded soil when temperatures are cool.  If a human ingests infective eggs, the eggs hatch into larvae, and the larvae will migrate throughout the individual’s body.  Humans are considered dead-end host for this parasite and human-to-human transmission does not occur.

In many people, Toxocara infection is mild and self-limiting.  However, some people will develop ocular toxocariasis or visceral toxocariasis.  Ocular toxocariasis occurs when the larvae migrate to the eye and can result in permanent vision loss or impairment.  Usually, only one eye is affected.  Visceral toxocariasis occurs when larvae migrate through various body organs, such as the liver or brain.  Symptoms can include fever, fatigue and coughing, wheezing or abdominal pain.

Animals associated with toxocariasis include:

  • Cats:  Cats can be infected with Toxocara cati and shed the eggs in their feces.  After maturing, the eggs can then infect humans and other animals.
  • Dogs:  Dogs can be infected with Toxocara canis and shed the eggs in their feces.  After maturing, the eggs can then infect humans and other animals.

Toxocara Life Cycle

Steps to reduce your risk of toxocariasis:

  • Clean your pet's living area at least once a week.  Feces should be either buried or bagged and disposed of in the trash.  Wash your hands after handling pet waste.  Because eggs need two weeks in the environment before they become infective, keeping your pet’s living area clean will prevent environmental contamination.
  • Take your pets to the veterinarian to prevent infection with Toxocara.  Your veterinarian can recommend a testing and treatment plan for deworming.
  • Wash your hands with soap and water after playing with your pets or other animals, after outdoor activities and before handling food.
  • Teach children the importance of washing hands to prevent infection.
  • Do not allow children to play in areas that are soiled with pet or other animal feces.
  • Teach children that it is dangerous to eat dirt or soil.

Toxocariasis resources:


Last updated:  09/16/2014

Zoonotic Disease Program