Токсокары IgG

The Toxocara IgG antibody test (titer) measures immunoglobulin G directed against Toxocara canis to support the diagnosis of human toxocariasis. Anti-Toxocara IgG typically becomes detectable 6–8 weeks after exposure, rises to a peak at approximately 2–3 months, and may remain measurable for a prolonged period; titers often parallel disease burden and clinical severity. This serologic assay is used when visceral larva migrans or ocular toxocariasis is suspected, particularly in patients with peripheral eosinophilia or compatible organ involvement, and in individuals with relevant exposure risks (for example, veterinarians, animal handlers, dog trainers, and children with fever of unknown origin and eosinophilia). Ocular disease can yield low or equivocal serologic responses due to limited antigenic stimulation, and false-positive results may occur in persons with systemic lymphoproliferative disorders or immunodeficiency. As a result, Anti-Toxocara IgG (Toxocara antibodies, IgG) testing is interpreted in conjunction with clinical findings and epidemiologic history to confirm infection.

Toxocariasis results from human infection by the dog roundworm Toxocara canis. Canids are the definitive hosts, shedding eggs that mature in the environment; humans acquire infection by ingesting embryonated eggs from contaminated soil, animal fur, or inadequately processed foods. In the human host, larvae hatch in the proximal small intestine, penetrate the mucosa, and enter the portal circulation. Many lodge in the liver; others transit the pulmonary circulation to the lungs and subsequently disseminate systemically. Within tissues, larvae do not complete development in humans and ultimately die, becoming encapsulated and forming granulomas. Tissue damage reflects both mechanical injury to small vessels and the effects of excretory–secretory antigens that drive hypersensitivity. Disease severity relates to parasite burden and host allergic responsiveness. The liver and lungs are frequent targets, but the central nervous system (including the eyes), kidneys, and skeletal muscle may also be involved. Clinically, toxocariasis ranges from asymptomatic to overt visceral larva migrans with fever, malaise, lymphadenopathy, rash, gastrointestinal symptoms, right upper quadrant pain, hepatosplenomegaly, and respiratory findings. Ocular toxocariasis typically affects one eye and may present with decreased visual acuity, retinal granuloma, uveitis, endophthalmitis, optic neuritis, keratitis, or visualization of migrating larvae in the vitreous. Peripheral blood eosinophilia is a characteristic laboratory feature, and severe complications can occur in immunocompromised patients with heavy larval burden. Humans are paratenic hosts; therefore, adult worms and eggs are not detected in stool or duodenal specimens, which complicates diagnosis relative to other helminthiases. Toxocariasis is not transmitted person-to-person. Diagnosis integrates compatible clinical findings, eosinophilia, epidemiologic exposure, and serologic evidence of Anti-Toxocara IgG. False-positive serology can occur in individuals with systemic lymphoproliferative disorders or immunodeficiency, whereas ocular disease may yield low or indeterminate antibody levels because of limited antigen exposure. Prevention emphasizes hand hygiene after contact with soil or animals, avoidance of inadequately processed foods, and routine veterinary screening and deworming of dogs.