Ocular larva migrans (OLM) is caused by larval migration through the posterior segment of the eye and is a leading infectious cause of blindness in children in developed countries.  OLM classically presents with unilateral vision loss in a child, most often between the ages of five to ten.  The exam may demonstrate uveitis, retinitis, choroiditis, or endophthalmitis based on the location of the parasite.  The infection can also result in secondary glaucoma. Histologically, eosinophilic abscesses with surrounding granulomatous reactions are the expected manifestations.

Visceral larva migrans (VLM) is caused by larval migration through both solid and hollow organs in the abdomen and should be considered in any child presenting with fever, nausea, vomiting, abdominal pain and eosinophilia. An exam may be notable for hepatosplenomegaly, which can serve as a clue for clinicians that the presentation is not simple viral gastroenteritis.  Lung involvement can result in bronchospasm and wheezing.

Central nervous system disease is rare but can be severe and range from eosinophilic meningitis to fulminant meningoencephalitis, presenting with seizures, encephalopathy or neuropsychiatric symptoms.[7][8]

Diagnosis of toxocariasis is difficult. While identification of the organism on microscopy is the gold standard, it is rarely achieved for practical reasons.  ELISA assays are available and recommended; yet, they, unfortunately, have relatively poor sensitivity (approximately 80%).[9] Additionally, given that humans are not definitive hosts for Toxocara, stool microscopy is ineffective.  Other secondary indicators of infection include eosinophilia and hypergammaglobulinemia.  However, these markers are not specific, and their sensitivities do not have extensive backing in the literature. Clinical diagnosis and presumptive treatment is an option to consider in the right clinical context.

For the treatment of VLM, albendazole and mebendazole both are effective. Albendazole is recommended as it has superior tissue penetration than mebendazole.  The dose of albendazole is 10 mg/kg/day divided into two doses for five days.  Depending on other endemic infections, ivermectin and DEC (diethylcarbamazine) may be useful as well.  Treatment of OLM is more difficult and revolves around decreasing inflammation.  Thus, prednisone is often an addition to antihelminthic agents and surgery is reserved for only the most severe cases.[7][9]

The differential diagnosis for VLM is broad as many infections may cause eosinophilia and fever.  As this is a global disease, local epidemiology is paramount.  Considerations include ascariasis (Löffler’s syndrome), trichinosis, strongyloides, onchocerciasis, schistosomiasis, paragonimus, entamoeba histolytica, and Fasciola hepatica. 

The central differential for OLM is retinoblastoma.  The disease was originally discovered in the 1950s in enucleated eyes suspected to have retinoblastoma.

Eosinophilic meningitis has a narrow differential diagnosis as well: angiostrongylus (rat-lung worm) is the chief consideration.

The prognosis for VLM is generally good; however, chronic disease has potential correlations with both epilepsy and cognitive delay.  Some children may develop loss of vision. Other complications reported include myocarditis, pneumonia and henoch schonlein purpura.

Per above, complications, while rare, include blindness, severe neurologic disease, and even death.

Given that toxocariasis spreads via the fecal-oral route, patient education in hand-hygiene is vital in risk factor modification. Also, patients should receive instruction on other risk factors such as exposure to pets and places where animal feces are present such as sandboxes. Common pitfalls amongst healthcare providers include failure to consider this diagnosis in children.  The true disease burden is likely underestimated, and while failure to diagnose VLM may not carry acute complications, the chronic and economic burden of disease is likely profound.[3]

The management of Toxocara is complicated as it is more than human disease and requires a One Health approach.  Domestic animal carrier rates directly impact the risk of acquisition, vertical transmission is common in dogs and cats, and no vaccine exists.  Thus, interprofessional collaboration is necessary for adequate control.   The first challenge is increasing awareness.  Toxocara is considered a neglected tropical infection, given the minimal level of research, funding, and publicity it receives in spite of carrying a significant burden of disease. The role of the primary caregiver and nurse practitioner is invaluable in educating patients on preventing this parasitic infection.