Antifertility effects of quinestrol in male lesser bandicoot rat, Bandicota bengalensis, and potential in managing rodent population under field conditions.

Integrating fertility control techniques using steroid hormones after lethal control can help reduce post control rebuildup of rodent populations. The current study is the first to assess the antifertility effects of quinestrol in male lesser bandicoot rat, Bandicota bengalensis which is the predominant rodent pest species in Southeast Asia. Rats in different groups were fed bait containing 0.00%, 0.01%, 0.02%, and 0.03% quinestrol for 10 days in laboratory and evaluated immediately, and 15, 30, and 60 days after treatment discontinuation for effect on reproduction and other antifertility parameters. Effect of 0.03% quinestrol treatment for 15 days was also observed in managing rodent populations in groundnut crop fields. Treatment resulted in average consumption of 19.53 ± 1.80, 67.63 ± 5.50, and 246.67 ± 1.78 mg/kg bwt active ingredient by three treated groups of rats, respectively. No reproduction was observed in female rats mated with male rats treated with 0.03% quinestrol, even 30 days after cessation of treatment. Post-mortem examination showed a significant (P < 0.0001) effect of treatment on organ weights (testis, cauda epididymis, seminal vesicles, and prostate gland) and different sperm parameters (sperm motility, sperm viability, sperm count, and sperm abnormality) in the cauda epididymal fluid with partial reversibility after 60 days. A significant (P < 0.0001) effect of quinestrol on the histomorphology of testis and cauda epididymis was observed, suggesting its effect on spermatogenesis. Affected cell association and cell count in seminiferous tubules did not fully recover within 60 days of stopping treatment. Evaluation of the effects of quinestrol treatment in groundnut fields showed greater reductions in rodent activity in fields treated with 2% zinc phosphide followed by 0.03% quinestrol treatment as compared to fields treated with 2% zinc phosphide alone. Research concludes that quinestrol has the potential to reduce fecundity and post control rebuildup of B. bengalensis populations, but long-term studies of the effectiveness of quinestrol under large-scale field conditions are needed to use it as part of an integrated pest control program for rodents.

Effect of quinestrol on body weight, vital organs, biochemicals and genotoxicity in adult male lesser bandicoot rat, Bandicota bengalensis.

The present study was aimed to evaluate the toxic effects of quinestrol (a synthetic estradiol) in male lesser bandicoot rat, Bandicota bengalensis. Effect was studied on body weight, weight of vital organs, changes in level of biochemical parameters and genotoxicity. Feeding of bait containing 0.01% quinestrol in bi-choice and 0.02 and 0.03% quinestrol in no-choice for a period of 10 days resulted in total ingestion of 19.50, 67.60 and 243.30 mg/kg bwt, respectively of the active ingredient. Autopsy of rats after 15 and 30 days of treatment withdrawal revealed no significant effect on body weight and weights of vital organs of rats. A significant decrease in the testicular levels of 17-beta hydroxysteroid dehydrogenase and increase in total soluble proteins was observed in rats treated with 0.02 and 0.03% quinestrol. The plasma levels of lipid peroxidation in the form of malondialdehyde concentration and lactate dehydrogenase increased significantly whereas the level of testosterone decreased significantly in treated rats. The plasma levels of acid and alkaline phosphatases, superoxide dismutase and total proteins differed non-significantly among rats of treated and untreated groups. The effect was found reversed partially in rats autopsied after 60 days of treatment withdrawal. No micronuclei in bone marrow cells, no aberrations in chromosomes and no DNA damage in blood cells during comet assay indicated no genotoxic effect of quinestrol on B. bengalensis at the test doses administered. The results thus revealed that quinestrol causes reversible toxic effects in the form of oxidative stress, increased lytic enzyme activity and decreased steroidogenesis which may further lead to testicular damage thereby inhibiting reproductive function. Also more effect was shown at higher doses ingested in no-choice test as compared to low doses ingested in bi-choice tests.