Many human infections are asymptomatic, with only eosinophilia and positive serology.
The two main clinical presentations of toxocariasis are visceral larva migrans (VLM) and ocular larva migrans (OLM).
In VLM, which occurs mostly in preschool children, the larvae invade multiple tissues (liver, heart, lungs, brain, muscle) and cause various symptoms including fever, anorexia, weight loss, cough, wheezing, rashes, hepatosplenomegaly, and hypereosinophilia.
Death can occur rarely, by severe cardiac, pulmonary or neurologic involvement.
In OLM, the larvae produce various ophthalmologic lesions, which in some cases have been misdiagnosed as retinoblastoma, resulting in surgical enucleation.
OLM often occurs in older children or young adults, with only rare eosinophilia or visceral manifestations.
In this parasitic disease the
diagnosis does not rest on identification of the parasite. Since the larvae do not develop
into adults in humans, a stool examination would not detect any Toxocara eggs.
However, the presence of Ascaris and Trichuris eggs in feces, indicating
fecal exposure, increases the probability of Toxocara in the tissues.
For both VLM and OLM, a
presumptive diagnosis rests on clinical signs, history of exposure to puppies, laboratory
findings (including eosinophilia), and the detection of antibodies to Toxocara.
VLM is treated
with antiparasitic drugs, usually in combination with antiinflammatory
medications. The antiparasitic drug recommended in The Medical
Letter is albendazole*, with mebendazole* as an alternative. For
additional information, see the recommendations in
The Medical Letter (Drugs for Parasitic Infections).
* This drug is approved by the FDA, but considered investigational for this purpose.