Effects of avermectin on immune function and oxidative stress in the pigeon spleen

Avermectin (AVM) is a pesticide that can accumulate in the environment through spray-drift, runoff or field drainage. Residues of AVM or its metabolites in livestock feces have toxic effects on non-target aquatic and terrestrial organisms. In this study, changes in oxidative stress and immunity in pigeon spleen tissues were detected after subchronic exposure to AVM for 30, 60, and 90 days. In pigeon spleen, the activities of total anti-oxidation capability (T-AOC), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) decreased significantly, whereas the levels of malondialdehyde (MDA), protein carbonyl (PCO), and DNA-protein crosslink (DPC) coefficients increased. Additionally, obvious ultrastructure alterations were observed. These results indicated that AVM induced oxidative stress and damaged the normal structure of spleen cells. The exposure to AVM could lead to increases in the mRNA levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-4 (IL-4), as well as a decrease in the mRNA level of interferon-γ (IFN-γ), in a dose-time-dependent manner in pigeon spleen. The results imply that AVM induces immunosuppression in the spleen tissue of pigeons. The information presented in this study may be helpful for understanding the mechanism of AVM-induced immunotoxicity in birds.