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Toxocarosis: serum antibodies to Toxocara canis
Medical expert of the article
Last reviewed: 05.07.2025
The diagnostic titer of antibodies to Toxocara canis in serum is 1:800 or higher.
Toxocariasis is a widespread disease. The causative agent of toxocariasis is the nematode Toxocara canis, which usually parasitizes dogs, wolves, foxes and other representatives of the canine family. The clinical symptoms of the disease are varied. Depending on the predominant symptoms, visceral (23%) and ocular (67%) forms are distinguished. Toxocariasis often resembles ascariasis in its clinical manifestations. The most constant symptom of toxocariasis is high eosinophilia of the peripheral blood - up to 60-80%. In severe forms of the disease, granulomatous lesions of various organs and tissues can be detected.
Diagnosis of toxocariasis is difficult. This is due to the fact that in the human body toxocara do not reach sexual maturity, so it is impossible to detect adult individuals or their eggs in samples of feces or duodenal contents, as with other helminthiases.
The main method for diagnosing toxocariasis is the detection of IgG antibodies to Toxocara canis in the blood serum by ELISA with toxocara antigen when examining the blood serum of individuals with a characteristic set of symptoms: lymphadenopathy, hepatomegaly, bronchitis, bronchial asthma of unknown genesis, urticarial rash against the background of blood eosinophilia, leukemoid reaction of the eosinophilic type with a characteristic epidemic history (for example: geophagy), etc. The degree of increase in the antibody titer in the blood correlates with the severity of the disease. In patients with symptoms characteristic of toxocariasis, antibody titers in ELISA of 1:800 and above confirm the clinical diagnosis. In individuals without clinical symptoms, an antibody titer of 1:400 and below indicates contact of the person with the pathogen without the development of a pathological process.
False positive test results are possible in individuals with systemic lymphoproliferative diseases and immunodeficiency. This leads to the need to analyze the clinical picture of the disease. False negative and questionable test results are possible in individuals with eye lesions caused by toxocara as a result of weak antigen exposure. Individuals with a low positive ELISA result (titer 1:200-1:400) are registered with a dispensary and undergo serological testing every 3 months. When a clinical picture of the disease appears and specific antibody titers increase, the doctor decides on treatment. Repeated studies of the antibody content in the patient's blood allow assessing the effectiveness of the treatment - a decrease in the antibody titer indicates its effectiveness.