Effects of imidacloprid contaminated feed exposure on the spleen, lymph node, and mucosa-associated lymphoid tissues of adult male rabbits (Oryctolagus cuniculus)

Pesticide is one of the top chemical substances that pose a serious risk to public health. Imidacloprid (IMI) is a widely used broad-spectrum insecticide over the past decade. Here, oral IMI-contaminated green grass (at the dose rate of 100 mg/liter and sprayed) was fed to adult male rabbits (n=6), every alternate day for up to 90 days. The control rabbits (n=6) were fed pesticide-free green grass, wheat bran, and water ad libitum. For gross and histopathology, spleen, lymph nodes, and mucosa-associated lymphoid tissues were collected by ventromedial opening. No evident gross changes were found during the collection of the organs. Histopathologically, lymph nodes showed atrophy and degenerative lymphoid follicles. The cortex and medulla of the lymph nodes were less differentiated. The size and number of the lymphoid follicles in the cortex were also reduced in IMI-exposed rabbits. The spleen exhibited atrophic changes in the white pulps. The white pulp revealed degenerative changes with the depletion of the lymphoid tissues. As for the red pulp, it showed an irregular and depleted mesh network of reticular fibers in IMI-exposed rabbits compared to the control. The trachea and esophagus of IMI-exposed rabbits showed infiltration of the mononuclear cells in the propria-submucosa and tunica adventitia, respectively. The infiltration of mononuclear cells population was loaded in the core of the villi, tunica mucosa, and propria-submucosa of the duodenum, jejunum, and ileum of the IMI-exposed rabbits compared to the control. The present study findings suggest that IMI has toxic effects on the lymphoid organs and tissues of adult rabbits.