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Genetic and Rare Diseases Information Center (GARD)



* Not a rare disease

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Toxocariasis is a parasitic condition caused by the larvae of two species of Toxocara roundworms: Toxocara canis (from dogs) and Toxocara cati (from cats). Many people who are infected with Toxocara never develop any signs or symptoms of the condition. In those who do become sick, symptoms may present as:
  • Ocular Toxocariasis - when the larvae infect the eye and cause vision loss, eye inflammation, and/or damage to the retina.
  • Visceral Toxocariasis - when the larvae infect various organs of the body (i.e. the liver or the central nervous system) and cause fever, fatigue, coughing, wheezing, and/or abdominal pain.
Toxocariasis is generally spread through dirt that has been contaminated with animal feces that contain infectious Toxocara eggs. Young children and owners of dogs and cats have a higher chance of becoming infected. Visceral toxocariasis is treated with antiparasitic medications. Treatment of ocular toxocariasis is more difficult and usually consists of measures to prevent progressive damage to the eye.[1][2]


Last updated: 11/16/2015


  1. Parasites - Toxocariasis. Centers for Disease Control and Prevention. January 2013;
  2. Sun Huh, MD, PhD. Toxocariasis. Medscape Reference. August 2014;
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Basic Information

  • You can obtain information on this topic from the Centers for Disease Control and Prevention (CDC). The CDC is recognized as the lead federal agency for developing and applying disease prevention and control, environmental health, and health promotion and education activities designed to improve the health of the people of the United States.
  • DermNet NZ is an online resource about skin diseases developed by the New Zealand Dermatological Society Incorporated. DermNet NZ provides information about this condition.
  • The Merck Manuals Online Medical Library provides information on this condition for patients and caregivers. 
  • The National Organization for Rare Disorders (NORD) is a federation of more than 130 nonprofit voluntary health organizations serving people with rare disorders. Click on the link to view information on this topic.

In Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs.  Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Toxocariasis. Click on the link to view a sample search on this topic.
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.