Fertility control of Arvicanthis niloticus (Rüppel, 1842, Rodentia: Murinae) a major agricultural rodent pest: Implication for sustainable rodent pest management in Tigray, Ethiopia

Abstract

Rodent pests, including the African grass rat (Arvicanthis. niloticus), cause significant agricultural damage in Tigray. This study was carried out to evaluate the effects of Quinestrol (QE), Levonorgestrol (LV), and their combination (QL) on reproduction fertility of African grass rat A. niloticus. A total of 160 A. niloticus (80 males and 80 females) were used to evaluate bait acceptance and reproductive performance of A. niloticus at concentrations of 10, 50, and 100 ppm. After ten days of acclimatization, the animals were fed the contraceptive baits for seven days for the females and fourteen days for the males before being paired and sacrificed for histological observation. The examination involved dissecting female animals over eight days and male animals over fifteen days, examined and weighted the reproductive organs of A. niloticus (ovaries, uterus, testes, seminal vesicles, and epididymis) to assess their reproductive health and fertility. Fertility control compounds significantly (p < 0.0001) reduced bait acceptance and body weight compared to control except LV at 10 ppm. Treatment and sex had significant interaction effects (p < 0.001) on bait acceptance and body weight. Treated females showing slightly higher bait consumption than males. Quinestrol (QE) and its combination (QL) significantly (p < 0.001) reduced reproductive organ in A. niloticus compared to untreated animals, while levonorgestrel (LV) had no such effect. Quinestrol also significantly (p < 0.001) decreased the weight of male reproductive organs and negatively impacted on sperm concentration and motility with increased sperm abnormalities, which contributed to its antifertility effect. There was significant difference (p < 0.001) in the weight of female reproductive organs (ovary, uterus) between treated and untreated rodents. Quinestrol and its combination (QL) treatment at higher concentrations were caused mild edema, increasing uterine and ovarian weight which indicates a physiological response to estrogen stimulation involving tissue explosion and fluid retention. Quinestrol at 50 ppm was evaluated for its impact on reproductive success and had significant effect on pregnancy rate and litter size when both male and female A. niloticus were treated. These results demonstrated that the reproduction rate of A. niloticus can be suppressed by Quinestrol which proved to have antifertility effect.