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

Abstract

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.