Visceral Larva Migrans 

  • Author: Raymond D Pitetti, MD, MPH; Chief Editor: Russell W Steele, MD   more...
 
Updated: Aug 19, 2011
 

Background

Several roundworm parasites found in domestic animals can infect humans. Parasites are usually found in the larval stages in human tissues and provoke the clinical condition referred to as larva migrans. Toxocara species, the ascarid of dogs and cats, is most commonly associated with larva migrans. Classic visceral larva migrans (VLM) typically occurs in preschool-aged children with a history of eating dirt. Children can present with severe infection and can suffer from seizures, myocarditis, and encephalitis. Death has also been reported in some cases.

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Pathophysiology

Children contract Toxocara infections by ingesting embryonated eggs. The larvae hatch in the small intestine, invade the mucosa, and enter the portal system. The liver traps some larvae, but other larvae proceed to the lungs and the circulatory system, where they can disseminate to virtually every organ. In particular, the larvae often deposit in the liver, lungs, eye, heart, and brain. However, the parasite cannot complete its life cycle in humans. Larvae persist in tissues, provoking a granulomatous reaction and eventually dying. As a result, abscesses or granulomas form. Clinical manifestations depend on the tissue damage caused by the invading larvae and the associated immune-mediated inflammatory response.

See the image below.

Diagram of the Toxocara canis life cycle image. CoDiagram of the Toxocara canis life cycle image. Courtesy of the Centers for Disease Control and Prevention.
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Epidemiology

Frequency

United States

The seroprevalence of Toxocara infection in children varies from 2-10%.

International

Although most reported cases occur in the United States, international incidence is likely similar or slightly higher.

Mortality/Morbidity

Death is rare. Long-term morbidity is present with ocular larva migrans (ie, loss of vision in the affected eye) but not usually with visceral larva migrans. Chronic eosinophilic pneumonia, myocarditis, and Henoch-Schönlein purpura have been associated with visceral larva migrans.

Race

Infection rates are higher among blacks and Hispanics, likely because of greater exposure to the parasite.

Sex

Visceral larva migrans has no sex predilection.

Age

Infection primarily occurs in children aged 1-4 years but can occur at any age.

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Contributor Information and Disclosures
Author

Raymond D Pitetti, MD, MPH  Associate Professor, Department of Pediatrics, Division of Pediatric Emergency Medicine, University of Pittsburgh School of Medicine; Associate Division Chief, Division of Pediatric Emergency Medicine; Associate Medical Director, Emergency Department; Medical Director, Sedation Services; Medical Director, Express Care; Medical Director, Patient Safety; Consulting Staff, University of Pittsburgh Physicians

Raymond D Pitetti, MD, MPH is a member of the following medical societies: Allegheny County Medical Society, American Academy of Pediatrics, Pennsylvania Medical Society, and Society for Pediatric Research

Disclosure: Nothing to disclose.

Specialty Editor Board

Robert W Tolan Jr, MD  Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine

Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility

Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; Sanofi Pasteur Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Leslie L Barton, MD  Professor Emerita of Pediatrics, University of Arizona College of Medicine

Leslie L Barton, MD is a member of the following medical societies: American Academy of Pediatrics, Association of Pediatric Program Directors, Infectious Diseases Society of America, and Pediatric Infectious Diseases Society

Disclosure: Nothing to disclose.

Daniel Rauch, MD, FAAP  Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine

Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine

Disclosure: Baxter Honoraria Consulting

Chief Editor

Russell W Steele, MD  Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine

Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association

Disclosure: Nothing to disclose.

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Diagram of the Toxocara canis life cycle image. Courtesy of the Centers for Disease Control and Prevention.
 
 
 
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