In Vitro Anthelmintic Activity of Methanol Extracts of Selected Kenyan Medicinal Plants against Haemonchus contortus
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Date
2025-09
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Kenyatta University
Abstract
Agriculture contributes to a quarter of the gross domestic product in our beloved country Kenya with the livestock sector contributing 45% of its total. There are many constraints that hamper livestock production. Among them, helminthiasis is associated with deaths among sheep, weight loss and reduced production. Anthelmintic drugs are used in treating and control of helminth infections. The current emergence of resistance to anthelmintic drugs added to their high cost has necessitated developing regimens that are more effective, cheap, and eco-friendly compounds in battling the war against helminths. Plants which are abundant and cheap offer a promising alternative to circumvent resistance and spiralling cost of drugs. In Kenya plants have been traditionally used for treating helminthiasis, however there lacks scientific prove of their efficacy. This study evaluated the efficacy of Bridelia micrantha, Aframomum zambesiacum, Hagenia abyssinica, Rubus apetalus, Thespesia garckeana, Physalis peruviana and Caesalpinia volkensii traditionally used by the Meru and Tharaka Nithi community for parasitic worm infections, against Haemonchus contortus. The study entailed screening of the methanolic extracts of the above plants against Haemonchus contortus, both drug susceptible and isolates resistant to albendazole from sheep. Efficacy of these plants extracts was tested in an in vitro system using eggs and larvae of Haemonchus contortus. Egg hatchability was determined after 48-hour incubation with extracts while with larvae survival was determined after six days incubation. Physiological saline was used as negative control while positive controls used included albendazole and levamisole for susceptible and resistant isolates respectively. The experiments were carried out in triplicates. One-way ANOVA was used for analysis followed by Tukey’s post hoc test. P. peruviana and R. apetalus, inhibition percentages of 95.24±0.54, 90.00±1.00, 88.24±0.66 and 96.55±0.45, 85.71±0.79, 82.14±0.76 at 50mg/ml, 25mg/ml and 12.5 mg/ml respectively with no significant difference (P<0.05) in the egg hatch assay for susceptible isolates with the positive control. For the egg hatch assay with the resistant isolates, the highest mean inhibition percentages were observed with dilutions of 50 mg/ml achieving 93.42±0.46, 91.67±0.47, 94.56±0.36 and 91.80±0.59 with R. apetalus, B. micrantha, C. volkensii and H. abyssinica respectively with no significant difference (P<0.05) between them and levamisole. In the larvae developmental test for the susceptible isolates the highest mean percentage larvicidal activity of 100.00±0.00 was achieved with extracts from R. apetalus and H. abyssinica across the three dosages with no significant difference between the two and albendazole. For the L3 larvae from the resistant isolates reduced larvicidal activity was recorded with 78.38±0.48, 58.33±0.37 and 52.00±0.16 at 50mg/ml for R. apetalus, C. volkensii and T. garckeana respectively which had a statistically significant difference compared to levamisole. Synergism between the extracts with albendazole was conducted against the resistant L3 isolates where increased larvicidal activity was achieved with 98.46±0.32 for R. apetalus at 50mg/ml which had no significant difference at P<0.05. The MIC50 was determined where R. apetalus had 3.37mg/ml. Phytochemical analysis through GC-MS was also conducted on the plant extracts where compounds such as terpenoids were conspicuously present in the extracts which could account for some of the activity observed. However, from this study, supplementary studies are recommended to elucidate the phytochemicals accountable for the anthelmintic activity demonstrated by the plants in this study.
Description
A Thesis Submitted in Partial Fulfilment of the Requirement for the Award of the Degree of Master of Science (Biochemistry) in the School of Pure and Applied Sciences of Kenyatta University, September 2025
Supervisor:
1.Joseph J. N. Ngeranwa,
2.John K Mwonjoria
3.Joseph Nginyi