The prospective of using plants with antifertility effects in controlling the rodent pest, mastomys natalensis

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Date

2022

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Sokoine university of agriculture

Abstract

The prolific nature of some rodents has been a significant threat to the livelihood and public health in sub-Saharan Africa escalating the use of rodenticides. Regrettably, rodent pests are increasingly becoming resistant to rodenticides due to bait shyness or resisting death. Also, the rodenticidal poison has been killing other untargeted species of animals. Thus, alternative methods of rodent control including the use of birth control methods are increasingly being explored. So, the current study investigated the antifertility potential of Acacia nilotica pods and Albizzia lebbeck stem bark extracts in the Mastomys natalensis. Specifically, the study was done to investigate the effect of the plant's extracts on the fertility success rate of female and male M. natalensis, to evaluate the effect of the plant's extracts on follicular and corpora lutea counts in the female rat’s ovaries, to explore the effect of the plant’s extracts on the sperm cells parameters and histomorphology of the testes in the male rats and to determine the phytochemical constituents of the two plants. Pods of A. nilotica were collected from Kilwa and stem barks of A. lebbeck were collected from Morogoro urban, in Tanzania. The M. natalensis were collected from Sokoine University of Agriculture (SUA) owned farms. Experiments and Laboratory works were done at the College of Veterinary Medicine and Biomedical Sciences (CVBMS) at SUA. This thesis contains the research works done in the current study and is divided into three sections. Section one comprises introduction and literature review, problem statement, objectives, the rationale of the study, scope and limitations of the study. Section two encompasses the three manuscripts describing the research work done. The third section consists of the general conclusion and recommendation of the study. The first manuscript assesses the pathophysiological significance of A. nilotica pods aqueous extract and A. lebbeck stem bark methanolic extract on the reproductive system of female M. natalensis. A total of 60 sexually mature rats were randomized into a 2 x 3 factorial design for treatments (Control A. nilotica, and A. lebbeck) and treatment duration (7 or 14 days). Control rats consumed basal feed, treated rats consumed feed with 2% w/w of either of the plant extracts. At the end of treatment duration, treated female rats were cohabited with males for 16 days and sacrificed 20 days after the first day of cohabitation. Parameters assessed at necropsy included the pregnancy rates, number of fetal implantations, possible resorption sites, and fetal litter size. Other evaluated parameters included the ovarian weights, follicular and corpora lutea numbers, and general histopathology of ovaries. Results showed that pregnancy percentages, the number of fetal implantations, and fetal litter size were significantly reduced (p< 0.01) in rats under the A. nilotica and A. lebbeck extract treatments relative to the control. The ovarian weights of rats receiving the extracts did not differ significantly from the control (p > 0.05). However, the number of corpora lutea of pregnancy was significantly reduced (p < 0.001) in the ovaries of rats under extract treatments than in the control. Instead, the ovaries of rats receiving the two extracts contained a larger number of atretic follicles, signifying halted ovulatory and conception activities. In conclusion, the study demonstrated that dietary inclusion of crude extracts from A. nilotica pods and A. lebbeck stem bark can lead to decreased fertility success rates in M. natalensis female rats through suppression of ovulatory activities and induction of follicular atresia. The second manuscript evaluated the contraceptive potential of the methanolic extracts from A. nilotica pods and A. lebbeck stem bark in male M. natalensis. A total of 90 rats were randomized into a 3 x 3 factorial design for treatment (control, A. lebbeck and A. nilotica) (n = 10) and treatment durations (15, 30, or 60 days). Control rats consumed plain feed. Treated rats consumed feed with 2% w/w of either of the plant extract. Following treatment, male rats were mated to untreated females before sedation in ether and sacrification. Assessments were done on fertility success rates (number of impregnated females), weights of testes and reproductive glands, sperm cell parameters, and testes histopathology. Results revealed that the fertility success rate was reduced to 0% in the A. nilotica treated rats at all the treatment durations and in the A. lebbeck treated rats after 60 days of treatment. Moreover, the extract-treated rats revealed a significant reduction in the testes, seminal vesicles, and epididymides weights. Also, sperm cell density and the proportions of live and progressively motile spermatozoa were significantly reduced and there were numerous seminiferous tubules with damaged and thinned germinal epithelium and widened empty lumen in the extract-treated rats. In conclusion, treatment with A. nilotica or A. lebbeck extract in male rats reduced their fertility success rates through distortion of testicular structure and disruption of spermatogenesis. The third manuscript evaluated the phytochemical constituents of raw grounded materials and methanolic extracts of A. nilotica pods and A. lebbeck stem bark extracts and the potential effects the methanolic extracts may have on spermatozoa morphologies in the male M. natalensis. A portion of the grounded materials from each plant was extracted in 70% methanol. Both the grounded materials and corresponding methanolic extracts were assessed for the presence of phytochemicals with antifertility potentials. A total of 90 male rats were randomized into 9 groups based on treatment (control, A. lebbeck and A. nilotica) (n = 10) and extract treatment durations (15, 30, or 60 days). Results indicated that flavonoids, tannins, saponins, steroids, terpenoids and plant phenols were all present in the powdered raw materials and their corresponding extracts of both plants. However, saponin was shown to be more intensely present in the powdered and methanolic extracts of the A. lebbeck compared to those of A. nilotica while the reverse was true for flavonoids and tannins. Spermatozoa with normal head-abnormal tail, normal head-tailless, abnormal head-normal tail, both abnormal head and tail spermatozoa were more revealed in extracts treated rats relative to the control. In conclusion, the studied pods of A. nilotica and the Stem bark of A. lebbeck are rich in flavonoids, tannins, saponins, steroids, terpenoids and plant phenols which possess some antifertility properties explaining the adverse effects of the plant’s extracts on spermatozoa morphologies. The research information contained in this thesis contributes significantly to the limited available knowledge on the antifertility efficacies of medicinal herbal extracts in the wild rodents, more particularly the M. natalensis.

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Keywords

Rodent pest, Mastomys, Natalensis, Antifertility, Plants

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