Investigating the significance of the transgenerational impact of high and repeated doses of ivermectin: Effects on paternal testis histopathology, pups' development, and sexual behavior

Paternal exposure to environmental challenges is critical for the offspring's future health, and the transmission of acquired traits through generations increases the risk of offspring developing diseases. Ivermectin (IVM) is widely used in veterinary and human medicine to treat parasitosis. Our previous studies showed that IVM acute administration induced disorganization of the germinal epithelium and could cause damage to sperm production. Thus, this study investigated the effects of paternal exposure to repeated high ivermectin doses on paternal testis histology. After mating, their pups' development and sexual behavior in adult rats were examined. Method: Two groups of male rats were treated with IVM or its vehicle once a week for three weeks. We observed these males' body weight, organs and testis histology, and testosterone levels. These rats were mated with females without any treatment: the reproductive performance, the offspring development, and the male and female sexual behavior observed in adulthood. Relative to controls, the IVM paternal testis histology showed hypertrophy and hyperplasia of Leydig cells and increased diameter of the seminiferous tubules—no impairment in reproductive performance. In males and females, the physical and reflexes were modified. In adult age, female rats of the IVM group showed reduced sexual behavior and sexual preferences for the same sex, while male sexual behavior was not altered. Thus, it is possible that paternal exposure to IVM interfered with pups' hormonal and growth factors during development and in adult age. Further studies are needed to explore IVM transgenerational effects identifying possible mechanisms underpinning behavioral effects.