Toxocariasis is caused by migration of the larvae from the roundworm
Toxocara to organs and tissues. Toxocara larva migrans is the second most common helminthic infection in developed countries. Transmission is fecal-oral via the feces of infected dogs or cats. Parasites are not shed in the gastrointestinal tract, so diagnosis relies on serology or tissue examination. Tabs Content
Clinical Overview Diagnosis
Indications for Testing
Change in vision, eye inflammation or retinal damage in individual with potential for exposure to feces of infected dog or cat
Fever, fatigue, cough, wheezing in individual with potential for exposure to feces of infected dog or cat
Toxocariasis antibody detection (CDC) Nonspecific – CBC demonstrates eosinophilia in 30% of cases
Serology – IgG antibody testing
Cannot distinguish between past versus current infection
Clinical diagnosis may be hampered by inability to distinguish among parasitic infections that can also cause visceral larval migrans –
Baylisascaris procyonis, Fasciola hepatica, and Ascaris lumbricoides Histology
Biopsy and pathologist examination may provide definitive diagnosis.
Ocular – granulomatous diseases such as
and Mycobacterium tuberculosis sarcoidosis Dermatologic symptoms
Dermatitis Hot tub folliculitis
Other helminthic diseases – strongyloides, loiasis
Incidence – one of the most common parasitic infections worldwide
Age – usually children
Transmission – ingestion of soil contaminated with embryonated
Toxocara eggs Organism
Toxocara species that infect humans are T. canis and T. cati Ingested eggs hatch into larvae, travel across gut wall, and migrate to liver or lungs through lymphatic and circulatory systems
Larvae then spread from lungs to other organs, causing damage by their migration and induction of granulomatous lesions
Visceral larval migrans (VLM)
Asymptomatic, with mild
eosinophilia Cutaneous symptoms common
Chronic prurigo, pruritus, and/or urticaria and eczema
Symptoms persist a year or more
Severe and potentially fatal symptoms
Ocular larval migrans
Acute eye lesions caused by penetration of larvae into eyes
Vision loss in affected eye
Neural larval migrans – fever, headache, seizures
Common larval migrans – similar to visceral larval migrans but less severe
ARUP Lab Tests
Aid in diagnosis of toxocariasis
If results equivocal, repeat testing in 10-14 days
Assess presence of eosinophilia
Akao N, Ohta N.
Toxocariasis in Japan. Parasitol Int. 2007; 56(2): 87-93. PubMed
Gavignet B, Piarroux R, Aubin F, Millon L, Humbert P.
Cutaneous manifestations of human toxocariasis. J Am Acad Dermatol. 2008; 59(6): 1031-42. PubMed
Gottstein B, Piarroux R.
Current trends in tissue-affecting helminths. Parasite. 2008; 15(3): 291-8. PubMed
Moreira GM, Telmo Pd, Mendonça M, Moreira AN, McBride AJ, Scaini CJ, Conceição FR.
Human toxocariasis: current advances in diagnostics, treatment, and interventions. Trends Parasitol. 2014; 30(9): 456-64. PubMed
Rubinsky-Elefant G, Hirata CE, Yamamoto JH, Ferreira MU.
Human toxocariasis: diagnosis, worldwide seroprevalences and clinical expression of the systemic and ocular forms. Ann Trop Med Parasitol. 2010; 104(1): 3-23. PubMed
Last Update: October 2019