Synergistic toxic and contraceptive potential of neem seed extract and andrographolide-based bait against black rat, Rattus rattus

Rodents cause damage in crop fields and commensal situations. This study aimed to prepare a ready-to-use, palatable, and stable bait using neem seed alcoholic hexane (NSAH) extract and andrographolide powder extract (APE) with toxic and antifertility properties for laboratory testing against wild-caught female Rattus rattus. Female rats were divided into four groups (n = 10 for each group). Rats of Groups I, II, and III were fed on treated baits 1, 2, and 3 for 25, 15, and 10 days, respectively, under bi-choice conditions, while group IV rats were fed on a control diet. Consumption, mortality, and reproductive parameters were recorded during the treatment period. After the treatment, rats left alive (n = 5) but lethargic due to the toxic effect of treated baits were necropsied. The results indicate that treated bait 2 is more palatable with maximum antifertility effect, while the toxic effect was more pronounced with treated bait 3. In group II, the duration of the estrous cycle was prolonged by 96.39% and normal follicles were absent. Cystic follicles were maximum in group II, followed by I, III, and IV. The thickness of the uterine layers and the number of uterine glands were minimized in group II. In conclusion, the study suggests that treated bait 2 is significantly more effective than treated bait 1 and 3 due to its increased palatability, stabilization, and synergistic effect of neem seed and andrographolide. Applying this bait in real field conditions will lead to instant and long-term reductions in the rodent population.