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Toxocarosis - Diagnosis
Last reviewed: 03.07.2025
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A lifetime parasitological diagnosis of toxocariasis is extremely rare and only possible when examining biopsy material, when toxocara larvae can be detected and verified in the tissues. Toxocariasis diagnostics is based on epidemiological history and clinical symptoms. The presence of persistent long-term eosinophilia is taken into account, although it is not always found in ocular toxocariasis. An indication of keeping a dog in the family or close contact with dogs, or geophagy indicates a relatively high risk of contracting toxocariasis.
Immunological diagnostics of toxocariasis is aimed at determining the content of specific IgG to the T. cams antigen in the blood serum using the ELISA method. It has high sensitivity and sufficient specificity for visceral localization of larvae - 93.7 and 89.3%, respectively, but is not informative enough for eye damage. An antibody titer of 1:400 indicates invasion, but not disease; a titer of 1:800 or higher indicates toxocariasis. In patients with the chronic form with severe pulmonary syndrome, the level of specific antibodies is usually moderately elevated (1:800 or 1:1600). However, this group of patients is naturally found to have an elevated content of specific anti-toxocara antibodies of the IgE class in the blood serum. Immunoblotting can be used to confirm the ELISA results. There is not always a correlation between the level of antibodies and the severity of clinical manifestations of toxocariasis, as well as between the level of antibodies and blood hypereosinophilia. Due to the cyclical course of invasion with relapses and remissions in dynamics, significant fluctuations in clinical, hematological and immunological parameters in the same patient are possible. It is recommended to include a biochemical blood test, X-ray examination of the lungs, and, if indicated, bronchoscopy, bronchography, ECG, ultrasound of the abdominal organs in the clinical study of patients with toxocariasis.
Differential diagnosis of toxocariasis
Differential diagnostics of toxocariasis is carried out with the early stage of helminthiases specific to humans (ascariasis, strongyloidiasis, schistosomiasis, opisthorchiasis), bronchial asthma, as well as with numerous diseases that are accompanied by eosinophilia in the peripheral blood (Löffler syndrome, tropical eosinophilia, chronic nonspecific polyarthritis in children, lymphogranulomatosis, cancer, drug sensitization, parietal fibroplastic myocarditis, etc.). Ocular toxocariasis must be differentiated from retinoblastoma and chorioretinitis of tuberculosis, cytomegalovirus and other etiologies. There are no reliable methods for diagnosing ocular toxocariasis. In many cases, the diagnosis is made only by histological examination. Ultrasound and CT of the eye are used for diagnostic purposes. Sometimes the diagnosis of "toxocariasis" can be made only on the basis of the effect of the course of antiparasitic treatment. The issues of diagnosis and treatment of patients with ocular toxocariasis are decided jointly by an ophthalmologist and an infectious disease specialist.
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