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Toxocara Antibody

Toxocariasis is a zoonotic parasitic disease caused by the nematode, Toxocara, of which there are 2 species: T canis and T cati. Approximately 5% of the US population is infected with Toxocara. Prevalence may be as high as 40% in some tropical countries. Children and a0dolescents under the age of 20, as well as dog owners, are at higher risk of infection.

Toxocara eggs are shed in the feces of infected animals. They become infectious within 2 to 4 weeks after shedding. Humans become infected through ingestion of dirt containing Toxocara eggs. Less commonly, humans can become infected by eating undercooked or raw meat from infected animals. After ingestion, Toxocara eggs hatch and release larvae. They can cross the intestinal mucosa, enter the bloodstream and migrate to the liver, heart, lungs, brain, muscles, and eyes. Toxocara larvae can cause severe local inflammatory reactions in these tissues.

Toxocariasis has two primary clinical presentations; visceral larva migrans and ocular larva migrans. Visceral larva migrans causes Loffler's syndrome (eg, fever, coughing, wheezing, abdominal pain), hepatomegaly, or eosinophilia. Ocular toxocariasis may cause retinal scarring, decreased vision, and leukocoria. Rarely, larvae cause eosinophilic meningoencephalitis or CNS granulomatous inflammation.

Stool examination for ova and parasites is not useful for diagnosing toxocariasis because eggs are not excreted by humans. The best test for toxocariasis is an enzyme-linked immunosorbent assay (ELISA) that detects IgG antibodies against larval antigens.

Reference Value is negative. A positive result is consistent with current or past infection. False-positive results may occur in patients with other helminth infections such as Ascaris lumbricoides, Schistosoma species, and Strongyloides.False-negative results may occur in severely immunosuppressed patients.

Specimen requirement is a red top tube of blood.

References

Smith HV: Antibody reactivity in human toxocariasis. In Toxocara and toxocariasis: clinical, speidemiological, and molecular persectives. Edited by JW Lewis, RM Maizels. London, UK: Institute of Biology and the British Society for Parasitology; 1993, pp 91-109

2. Liu EW, Chastain HM, Shin SH, et al: Seroprevalence of antibodies to Toxocara species in the United States and associated risk factors, 2011-2014. Clin Infect Dis. 2018;66:206-212

3. Woodhall DM, Fiore AE: Toxocariasis: A review for pediatricians. J Pediatric Infect Dis Soc. 2014;June;3(2):154-159

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