Human toxocariasis is a worldwide parasitic zoonosis, caused most commonly by the intestinal parasites the dog roundworm (Toxocara canis) and also the cat roundworm (Toxocara cati). Humans can contract the infection if they come into contact with contaminated soil and ingest the soil. The diagnosis of human toxocariasis is mainly based on clinical, epidemiological, and laboratory data, which include imagining exams, blood exams, eosinophilia, total IgE level, and serological tests. Definitive diagnosis of toxocariasis is based on the detection of Toxocara larvae from biopsy tissues, but this test is time-consuming and difficult to perform. Therefore, diagnosis is commonly based on clinical and serologic diagnosis. TES-ELISA using Toxocara excretory-secretory (ES) antigen and Western blot (WB) are the best choice for serodiagnosis of the generalised forms of toxocariasis. Initial serological findings should be confirmed by immunoblotting to avoid false-positive results and to evaluate cross-reactivity with other infective agents. The detection of other classes of immunoglobulins, namely IgE and IgA, the subclasses, namely IgG4 or circulating Ag was proven to be unable to discriminate between active and self-cured generalised toxocaral infections. Particularly for the diagnosis of ocular larva migrans, anti-T canis antibody in serum and vitreous or aqueous humour should be assessed, whereas the diagnosis of neurotoxocariasis should include the detection of specific antibodies and eosinophils in cerebrospinal fluid. Currently, the diagnosis of an active covert toxocariasis relies upon indirect arguments, e.g., the presence of otherwise unexplained symptoms along with blood eosinophilia and/or elevated levels of eosinophil cationic protein (ECP). This situation is far from ideal and more research should be carried out to solve this difficult problem.

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