Effects of imidacloprid-contaminated feed exposure on spermatogenic cells and Leydig cells in testes of adult male rabbits (Oryctolagus cuniculus)

This research was undertaken to assess the results of repeated exposure to the insecticide; imidacloprid (IMI)-contaminated feed on testicular tissue, spermatogenic cell population, Leydig cell number, and sperm morphology in adult male rabbits (n = 24). The treatment groups received IMI (Bildor® 100 mg/L water spray on green grass)-contaminated green grass without wash (n = 8, not-washed-feed rabbit group) and after wash (n = 8, washed-feed rabbit group) once daily for two weeks on an alternate day basis. The rest of the rabbits, as control, received a normal pesticide-free standard feed. During the exposure time, there was no evident toxic symptom found on regular monitoring of IMI-treated rabbits. Histopathologically, the thickness of tunica albuginea of testes reduced significantly with loosely arranged connective tissues in IMI-treated rabbits. Within the testes, the bizarre-shaped seminiferous tubules were seen with increased lumen diameter in IMI-treated rabbits. The spermatogenic cells were disorganized and detached from the basement membrane in seminiferous tubules of IMI-exposed testes of rabbits. The spermatogenic cell population decreased significantly (P < 0.05) in IMI-treated rabbits compared to control rabbits. Leydig cell number decreased significantly (P < 0.05) in IMI-treated rabbits. A high percentage of morphologically abnormal spermatozoa was seen in IMI-treated rabbits. The degree of the histopathological changes was more prominent in the testes of IMI-exposed not-washed-feed rabbits. The results showed that insecticide-IMI has toxicological effects on testicular tissues, mainly spermatogenic and Leydig cell population of adult rabbits which may cause infertility. A short running title: Effect of imidacloprid on testicular tissue of rabbits.