II. Epidemiology

  1. Incidence: 10,000 cases per year in United States
  2. Seroprevalance in United States: 13.9%

III. Pathophysiology

  1. Organism: Roundworms (Nematodes)
    1. Toxocara canis (dogs)
    2. Toxocara cati (cats)
  2. Transmission
    1. Dogs and cats ingest roundworm eggs in soil, feces
      1. Small mammals (rabbits) may act as intermediate hosts
      2. Female dogs or cats may transmit encysted larvae to puppies transplacentally or via Lactation
    2. Dog or cat feces contaminate soil
      1. Toxocara eggs incubate in feces for 2-4 weeks until larvae infectious
    3. Young children (age <3 years)
      1. Eat contaminated soil (Geophagia)
      2. Common in playgrounds and sandboxes (contamination rates are as high as 40%)
    4. Older children and adults
      1. Ingest undercooked meat or raw liver infected with Toxocara larvae
  3. Infection
    1. Infectious eggs ingested and hatch in Intestine
    2. Larvae trapped in liver or circulate and infect heart, lungs, brain, muscle, or eye
  4. Clinical manifestations are dependent on multiple factors
    1. Parasite load
    2. Host immune response
    3. Larvae migration path

IV. Findings: Toxocariasis Presentations

  1. Visceral Toxocariasis (children ages 2-4 years old)
    1. Inflammatory response in liver, heart, lungs, brain, muscle
  2. Ocular Toxocariasis
    1. See Ocular Larva Migrans
  3. Covert Toxocariasis (most common)
    1. Asymptomatic or mild symptoms

V. Symptoms: Visceral Toxocariasis (children ages 2-4 years old)

  1. Constitutional
    1. Fever
    2. Myalgia
    3. Anorexia
    4. Fatigue
  2. Pulmonary
    1. Wheezing
    2. Cough
  3. Gastrointestinal
    1. Nausea
    2. Abdominal Pain
    3. Hepatomegaly
  4. Neurologic
    1. Meningoencephalitis
  5. Skin
    1. Edema
    2. Urticaria

VI. Complications

  1. Epilepsy may develop in toddlers
  2. Ocular Larva Migrans (Endophthalmitis)

VII. Differential Diagnosis

  1. Hepatitis
  2. Encephalitis
  3. Viral myalgia
  4. Epilepsy
  5. Pneumonia
  6. Trichinosis
  7. Eosinophilic Leukemia
  8. Periarteritis nodosa

VIII. Labs

  1. Complete Blood Count
    1. Anemia
    2. Leukocytosis with >20% Eosinophilia
  2. Serology for Toxocara Antibody
    1. Does not distinguish acute versus prior infection
  3. Other findings/tests
    1. Larval antigen ELISA Test
    2. Hypergammaglobulinemia
    3. Avoid stool testing (larva and eggs will not be found in the stool)

IX. Course

  1. Typically a self limited course in most cases
  2. Generally benign

X. Management

  1. Indications
    1. Most cases are treated
    2. Severe cardiac or pulmonary disease
    3. Neurologic involvement
  2. Preparations
    1. Albendazole (Albenza)
      1. Dose: 7.5 mg/kg up to 400 mg orally twice daily for 5 days
      2. Preferred agent in United States
    2. Mebendazole (Vermox)
      1. Dose: 100-200 bid for 5 days
      2. Not available as of 2012 (use Albendazole instead)
    3. Diethylcarbamazine (Hetrazan)
      1. Dose: 6 mg/kg/day divided tid for 7-10 days
      2. Has been used outside U.S. to treat Visceral Larva Migrans
  3. Adjunctive
    1. Corticosteroids are indicated if inflammation present (especially with Ocular Larva Migrans)

XI. Prevention

  1. Careful child supervision
    1. Prevent soil ingestion
    2. Encourage hand washing
  2. Regular worming of cats and dogs
  3. Clean up after pets
  4. Cover sandbox between use
  5. Cook liver and other organ meats well before eating

XII. Resources

Images: Related links to external sites (from Google)

Ontology: Larva Migrans, Visceral (C0023049)

Definition (NCI) A parasitic infection caused by worms found in domestic animals. In humans nematode larvae enter the portal system from the small intestine and disseminate in visceral organs causing inflammatory reactions. Signs and symptoms include eosinophilia, hepatomegaly, splenomegaly, and lung infections.
Definition (MSH) A condition produced in man by the prolonged migration of animal nematode larvae in extraintestinal tissues other than skin; characterized by persistent hypereosinophilia, hepatomegaly, and frequently pneumonitis, commonly caused by Toxocara canis and Toxocara cati.
Concepts Disease or Syndrome (T047)
MSH D007816
ICD10 B83.0
SnomedCT 87121004
English Larva Migrans, Visceral, Migrans, Visceral Larva, LARVA MIGRANS, VISCERAL, Larva migrans, Visceral, Toxocara visceral larva migran, Visceral larva migrans, visceral larva migrans, visceral larva migrans (diagnosis), Visceral Larva Migran, Migran, Visceral Larva, Larva Migran, Visceral, Visceral Larva Migrans Syndrome, Larva Migrans, Visceral [Disease/Finding], larva visceral migrans, larva migrans visceral, Visceral larva migrans syndrome, Toxocaral visceral larva migrans, Visceral larva migrans syndrome (disorder), larva migrans; visceralis, visceral; larva migrans, Visceral Larva Migrans, Larva migrans visceralis
Swedish Larva migrans, visceral
Japanese ナイゾウヨウチュウイコウショウ, 幼虫移行症-内臓, 臓器幼虫移行症, 内臓幼虫移行症, 幼虫体内移行症, 幼虫内移行症, 幼虫内臓移行症, 内蔵幼虫爬行症, 幼虫内蔵爬行症, 臓器幼虫爬行症
Czech larva migrans viscerální, Larva migrans visceralis
Finnish Viskeraalinen vaeltava toukka
Russian LARVA MIGRANS VISTSERAL'NAIA, LARVA MIGRANS ВИСЦЕРАЛЬНАЯ
Korean 내장 유충 이행증
Portuguese Síndrome de Larva Migrans Visceral, Larva visceral migrante, Larva Migrans Visceral
Spanish Síndrome de Larva Migrans Visceral, Sindrome de Larva Migrans Visceral, síndrome de la larva migratoria visceral (trastorno), síndrome de la larva migratoria visceral, Larva migrans visceral, Larva Migrans Visceral
Polish Zespół larwy wędrującej trzewnej
Hungarian visceralis larva migrans
Dutch larva migrans; visceralis, visceralis; larva migrans, viscerale larva migrans, Larva migrans visceralis
French Micro-ascaridose, Larva migrans viscérale
German Larva migrans visceralis, Larva migrans, viszerale
Italian Larva migrans viscerale

Ontology: Toxocariasis (C0040553)

Definition (NCI) A parasitic infection caused by Toxocara. Humans are infected by the larvae of Toxocara canis and Toxocara cati from dogs and cats respectively. Most cases remain asymptomatic. The parasites may affect the eye, causing diminished vision, or other major organs, causing hepatomegaly, eosinophilia, wheezing, and coughing.
Definition (MSH) Infection by round worms of the genus TOXOCARA, usually found in wild and domesticated cats and dogs and foxes, except for the larvae, which may produce visceral and ocular larva migrans in man.
Concepts Disease or Syndrome (T047)
MSH D014120
ICD9 128.0
ICD10 B83.0
SnomedCT 406619001, 38995001, 76695000
English Toxocariases, Toxocariasis, TOXOCARIASIS, Toxocarosis, toxocariasis (diagnosis), toxocariasis, Infection due to Toxocara, Infection due to toxocara (disorder), Infection due to Toxocara (disorder), Infection due to toxocara, Toxocariasis [Disease/Finding], toxocarosis, Toxocara infection, Toxocariasis (disorder)
Dutch Toxocara-infectie, toxocariasis, Infectie, spoelworm-, Spoelworminfectie
French Infection à Toxocara, Toxocariase, Toxocarose
German Toxocarai-Infektion, Toxocarainfektion, Toxocariasis
Italian Infezione da Toxocara, Toxocariasi
Portuguese Infecção por toxocara, Toxocaríase
Spanish Infección por toxocara, toxocariasis (trastorno), toxocariasis, infección por Toxocara (trastorno), infección por Toxocara, Toxocariasis
Japanese トキソカラ症, トキソカラ感染, トキソカラカンセン, トキソカラショウ
Swedish Toxocariasis
Czech toxokariáza, Toxokaróza
Finnish Toksokariaasi
Russian TOKSOKAROZ, ТОКСОКАРОЗ
Polish Zespół wędrującej larwy trzewnej, Toksokaroza
Hungarian Toxocara fertőzés, toxocariasis