Visceral larva migrans (Toxocariasis) is a zoonotic, nematode infection. Humans become infected by eating contaminated soil or raw vegetables. Cats and dogs are the natural reservoirs. Infection is most common in 2-5 year-old children who eat soil. Puppies are commonly infected.
CASES/YEAR
10,000 (US); 200,000 (Global)
OTHER NAMES
VLM; Toxocariasis; Ocular larva migrans (OLM); Toxocara canis or T. cati infection; Baylisascariasis (Related Infection);
INCUBATION
Weeks to months; Shorter incubation (hours to days) reported after raw liver ingestion; [CCDM]
INITIAL SYMPTOMS
Usually a mild, chronic infection; Common findings: fever, eosinophilia, leukocytosis, and cough; [CCDM] Most light infections are asymptomatic. [Harrison ID] Usually children <6 years with history of eating contaminated soil; [PPID, p. 3473]
PRECAUTIONS
No direct person-to-person transmission; [CCDM]
COMMENTS
FINDINGS:
In patients with visceral larva migrans, marked eosinophilia may persist for months. Toddlers may present with fever, cough, wheezing, eosinophilia, leukocytosis, and pulmonary infiltrates. Another common presentation is fever, eosinophilia, and hepatomegaly. Common findings are arthralgias and hypergammaglobulinemia. Less common are splenomegaly and lymphadenopathy. Urticaria and skin nodules have been described. CNS infections are rarely reported--meningitis, encephalitis, mass lesions, and seizures. [Guerrant, p. 765; PPID, p. 3473-4]
EPIDEMIOLOGY:
Toxocariasis is a zoonotic, nematode infection. Humans become infected by eating contaminated soil or raw vegetables. Cats and dogs are the natural reservoirs. Occasionally humans are infected by eating raw liver of chicken, sheep, or cattle exposed to infected cats or dogs. "Internationally, seroprevalence ranges from lows of 0%-4% in Germany and urban Spain (Madrid) to 83% in some Caribbean subpopulations." [CCDM, p. 329-32] Infection is most common in 2-5 year-old children who eat soil. Puppies are commonly infected; therefore, regular deworming is recommended. [Merck Manual, p. 1679] OLM usually occurs in older children and young adults with no history of pica, and they usually do not have eosinophilia. [Harrison ID, p. 1128]
RELATED INFECTIONS:
Other causes of visceral larva migrans are Gnathostoma spinigerum, Capillaria hepatica, and Baylisascaris procyonis, a nematode infection of raccoons. A few cases of baylisascariasis have been documented in the USA. Eggs must mature in soil to become infective. Over 50% of raccoons are infected, and the habit of eating dirt puts young children at risk. The larvae cause severe or fatal CNS infections. Infections of the eye and heart have also been reported. [ID, p. 1533] Patients with Baylisascaris infections have increased CSF and peripheral eosinophils. [Cohen, p. 194t] See "Gnathostomiasis" and "Capillaria hepatica."
DIAGNOSTIC
ELISA tests are highly sensitive and specific for detecting VLM and OLM; [CCDM] ELISA tests for toxocaral antibodies confirm the clinical diagnosis; [Harrisons, p. 626]
SIGNS & SYMPTOMS
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>fatigue, weakness
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>fever
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G abdominal pain
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G hepatomegaly
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H anemia
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H eosinophilia
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H hypergammaglobulinemia
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H leukocytosis
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H lymphadenopathy
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H splenomegaly
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N headache
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N lethargy
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N seizure
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R cough
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R dyspnea
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R wheezing
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S rash (exanthem)
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S skin or subcutaneous nodule
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S urticaria
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X lung infiltrates
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*ARDS
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*arthritis
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*blindness
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*brain abscess or lesion
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*encephalitis
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*meningitis
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*myelitis
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*myocarditis
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*pericarditis
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*pneumonia
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*pneumonitis
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*uveitis
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*weight loss
SOURCE
Fecally Contaminated Soil, Animal Excreta, Animal Tissue, Soil or Dust (Ingesting or Inhaling), Eating Contaminated Food, Eating Contaminated or Infected Meat, Eating Contaminated Produce
RESERVOIR
Birds and Poultry, Cattle, Goats and Sheep, Cats, Dogs
RISK FACTORS
- Eat soil containing infective eggs
- Eat undercooked meat or fish
REFERENCES FOR CASES/YEAR
1. (US) 10,000 infections every year, usually in children < 6 years old; [Gorbach, p. 230]
2. (Global) Cases reported in England & Wales: 2 (2008), 1 (2009), 8 (2010), 0 (2011), 5 (2012); [Public Health England website] Guesstimate: global cases/yr = 20 times US cases/yr;