Infecção experimental de frangos com Toxocara canis: cinética e avidez de anticorpos IgY

Abstract

Toxocariasis is a geohelminth zoonosis with worldwide distribution, mainly through the ingestion of embryonated eggs of nematodes of the Toxocara genus. The disease can also be transmitted to humans as a result of eating raw or undercooked meat of parathenic hosts, such as birds. Studies on the humoral immune response through antibodies in chickens, however, are scarce. The aim of this study was to evaluate the production of IgY (IgG) in broiler chickens experimentally infected with Toxocara canis. Three groups (n=12 per group) of female broiler chickens (G1, G2 and G3), 34 days of age, were infected orally (gavage), with 100, 1000 and 5000 T. canis eggs, respectively. Another, non-infected group (G4, n=12), was assessed as the control. Blood samples were obtained at the following time points: 0 (pre-infection), 7, 14, 21, 28, 45 and 60 days post-infection (DPI). Kinetic and avidity index (AI) of IgY were determined using an enzyme-linked immunosorbent assay (ELISA) method. Receiver operating characteristic (ROC) curve analysis was performed for each time point, and subsequently analyzed to differentiate the initial or acute phase (7 to 21 DPI) and the final or chronic stage (28 to 60 DPI). The cutoff point was 0.368, and the test showed 91.7% sensitivity (CI 95%: 77.5-98.3) and 100% specificity (CI 95%: 92.6-100). The highest efficiency (97.0%) was observed at 60 DPI. Regarding the kinetics of antibodies, the seroconversion of the birds in the G2 and G3 groups occurred before (21 DPI) those in the G1 (28 DPI). The AI was medium at 21 DPI, becoming high after 28 DPI, indicating a chronic phase of infection. The results of the study demonstrate that the ELISA test could be a highly efficient tool for the detection of anti-Toxocara antibodies in birds, serving both for seroepidemiological studies and to evaluate the role of chickens as indicators of environmental contamination of Toxocara spp.