eMedicine Specialties > Pediatrics: General Medicine > Parasitology

Visceral Larva Migrans

Author: Raymond D Pitetti, MD, MPH, Associate Professor, Department of Pediatrics, Division of Pediatric Emergency Medicine, University of Pittsburgh School of Medicine; Consulting Staff, University of Pittsburgh Physicians
Contributor Information and Disclosures

Updated: May 22, 2009

Introduction

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.

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.


Diagram of the <em>Toxocara canis</em> life cycle...

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

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Diagram of the <em>Toxocara canis</em> life cycle...

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

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.

Clinical

History

  • Children with visceral larva migrans (VLM) may complain of loss of appetite, fever, cough, wheezing, or abdominal pain. 
  • Ask parents about the presence of household pets and if the child is known to eat dirt.
  • Ascertain a careful history regarding occupational and household chemical exposures, drug exposures, asthma, atopic dermatitis, travel to tropical areas, or the consumption of raw meat.

Physical

Causes

  • Toxocara canis is the most common cause of visceral larva migrans. Mature T canis worms live in the small intestines of dogs, their natural host. Heavily infected dogs can pass millions of eggs each day in their feces.3
  • Toxocara cati can also cause visceral larva migrans. 
  • Other etiologic agents include Baylisascaris procyonis, Capillaria hepatica, Ascaris suum, and some Ancylostoma species.

More on Visceral Larva Migrans

Overview: Visceral Larva Migrans
Differential Diagnoses & Workup: Visceral Larva Migrans
Treatment & Medication: Visceral Larva Migrans
Follow-up: Visceral Larva Migrans
Multimedia: Visceral Larva Migrans
References
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References

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Further Reading

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Keywords

visceral larva migrans, toxocariasis, Toxocara canis, Toxocara cati, VLM, parasitic infection, roundworm parasites, chronic eosinophilic pneumonia, myocarditis, Henoch-Schönlein purpura, eating dirt, ocular larva migrans, atopic dermatitis, asthma, hepatomegaly, splenomegaly, wheezing, rales, pruritic rash, urticaria, periorbital edema, strabismus, Löffler syndrome, seizure, abdominal pain, treatment, diagnosis

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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; 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.

Medical Editor

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

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Leslie L Barton, MD, Professor, Program Director, Department of Pediatrics, University of Arizona School 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.

CME Editor

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: None None None

 
 
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