Prolonged Exposure of Pyrethrin Insecticides Affects Reproductive Organs of Female Wistar Rats

Pyrethrins are pesticides found naturally in some Chrysanthemum flowers. They are commonly used to control mosquitoes, moths and many other pests. However, exposure to these Pyrethrins by direct or indirect inhalation by the population through various means could also pose potential risks to human health and the environment. Hence, this study aims to investigate the effect of chronic exposure of plant derived insecticides (pyrethrins) on female reproduction, using Wistar rats. Thirty (30) female wistar rats were randomly divided into three (3) groups (A, B and C). Group A was the control group, group B with mild exposure to the insecticide while group C with severe exposure to the insecticide for three weeks. Rats in each group were sacrificed after three (3) weeks of prolonged exposure to pyrethrin. Sera obtained from the rats were assayed for sex steroid hormones; Estradiol (E2) and progesterone, using Enzyme-linked Immunosorbent Assay (ELISA). Tissue samples of ovaries and gravid uteri were collected for histological processing. Vaginal smear samples were taken from each rat for the three (3) weeks of exposure. There was significant decrease in the body weights and relative uterine weight of the animals in groups exposed to pyrethrin, however, a significant increase was seen in ovarian weight of the test groups when compared to control. Serum hormonal levels of progesterone for the test groups were significantly increased while the serum estradiol level for the test groups was significantly reduced, when compared to the control group. There were pathological changes in the tissues of the ovaries and gravid uteri of the test groups compared to the control. There is significant difference in the progression of the estrous cycle of rats in the test groups when compared to control. More so, all rats presented a longer estrus phase and an irregular cycle by keeping same phase for long period. Hence, prolonged exposure to plant-derived insecticide (pyrethrin) affects female reproductive organs, steroid hormone synthesis and increase free radicals leading to oxidative stress. This may severely interfere with normal reproductive functions, and consequently lead to infertility.