Toxocarosis: antibodies to Toxocara canis in serum
Last reviewed: 18.10.2021
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The diagnostic titer of antibodies to Toxocara canis in serum 1: 800 and above.
Toxocarosis is a widespread disease. The causative agent of toxocarosis is the Toxocara canis nematode , usually parasitizes in dogs, wolves, foxes and other representatives of the dog family. Clinical symptoms of the disease are diverse. Depending on the prevailing symptoms, the visceral form (23%) and the ocular (67%) are isolated. Toxocarosis in clinical manifestations often resembles ascariasis. The most constant symptom of toxocariasis is high eosinophilia of peripheral blood - up to 60-80%. In severe forms of the disease, granulomatous lesions of various organs and tissues can be detected.
Diagnosis of toxocarias is complex. This is due to the fact that in the human body toxocarans do not reach sexual maturity, therefore it is impossible to identify adult individuals or their eggs in feces or duodenal contents, as in other helminthiases.
The main method of diagnostics of toxocarosis is the detection of IgG antibodies to Toxocara canis in the serum by ELISA with toxocar antigen in the study of blood serum in persons with a characteristic complex of symptoms: lymphadenopathy, hepatomegaly, bronchitis, bronchial asthma of unclear origin, urticaria rash against the background of eosinophilia of blood, leukemoid reaction eosinophilic type with a characteristic epidemic history (for example: geophagia), etc. The degree of increase in antibody titer in the blood correlates with the severity of the disease. In patients with symptoms typical of toxocariasis, antibody titers in ELISA 1: 800 and higher confirm the clinical diagnosis. In individuals in the absence of clinical symptoms, an antibody titer of 1: 400 and below indicates a person's contact with the pathogen without the development of a pathological process.
False positive results of the analysis are possible in persons with systemic lymphoproliferative diseases and immunodeficiency. This leads to the need for an analysis of the clinical picture of the disease. False negative and doubtful results of the analysis are possible in persons with eye toxocar involvement as a result of a weak antigenic effect. Individuals with a low positive ELISA result (titer 1: 200-1: 400) are placed on a dispensary record and serologic examination is carried out every 3 months. When a clinical picture of the disease appears and the titres of specific antibodies increase, the doctor decides on the treatment. Repeated studies of the content of antibodies in the patient's blood allow one to evaluate the effectiveness of the treatment - effectiveness is indicated by a decrease in the antibody titer.