In vitro assessment of selected ethno-medicinal plants as potential alternatives for the control of gastrointestinal nematodes in sheep and goats.
Mhlongo, Lindokuhle Christopher.
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Commercial anthelmintics are becoming ineffective against gastrointestinal nematodes (GIN) of ruminants due to development of resistant parasites. Research is exploiting anthelmintic ethno-medicinal plants for an alternative remedy. This study assessed the in vitro: (1) dose activity at different concentrations, (2) combined synergistic activity of ethanolic crude plant extracts on mixed GIN of sheep and goats; and (3) cytotoxic activity of these extracts on kidney vero cells. During assessment of in vitro dose activity, faecal samples of sheep and goats that were grazing on contaminated pasture were collected, cultured (12 days) to L3 larvae stage, and treated with 40, 20, 10, 5, 2.5, 1.25 and 0.25% v/v of Allium cepa, Ananas comosus, Bidens pilosa, Carica papaya, Crinium macowanii, Gunnera perpensa, Nicotiana tabacum, Ricinus communis, Sarcosterma viminale, Trema orientalis, Urtica dioica, Vernonia amygdalina, Zanthozylum capense, Zingiber officinale, Zizyphus mucronata and Aloe vanbalenii extracts. Larvae were subjected to Baermann technique for isolation and later observed under a microscope (10x objective). During the assessment of synergism at 1.25% v/v concentration (1:1), 28 crude plant extract combinations from eight (8) mostly edible plants namely: Allium cepa, Ananas comosus, Bidens pilosa, Carica papaya, Vernonia amygdalina, Zingiber officinale, Aloe vanbalenii and Nicotiana tabacum (inedible) were tested for their synergistic activity. The simple and Webb’s fractional product method were used to compute interactions of crude plant extract combinations. During assessment of cytotoxic activity MTT assay was used to assess effect of 16 individual plant extracts mentioned above on vero kidney cells. Results revealed that goats had a significantly higher efficacy than sheep at 40% (P=0.0253) and 20% (P=0.038) concentration (v/v); but goats had significantly lower efficacy at concentration (v/v) 1.25% (P= 0.0305) and 0.625% (P= 0.0158) relative to sheep. On the other hand, both goats and sheep had insignificant (P>0.05) efficacy for CPEs concentration (v/v) 10%, 5% and 2.5%. Plant species had no effect on efficacy at concentration (v/v) 40%, 20%, 10%, 5%, 2.5%, but had significant effect at lowest concentration (v/v) of 1.25 % (P=0.0085%) and 0.625 (P=0.0234%) which was not dose-dependent. Few plants had high activities at the lowest tested concentration (0.625% v/v). In goats it was Gunnera perpensa (89.47%±12.40), while in sheep Gunnera perpensa (100%±12.40), Urtica dioica (95.24%±12.40), Zizyphus mucronata (90.47%±12.40), Allium cepa (90.47%±12.40), Aloe vanbalenii (85.71%±12.40) and Bidens pilosa (80.95%±12.40). Interactions following Webb’s fractional product method were antagonistic and synergistic, whereas those following simple method yielded synergistic interactions only. In goats, V. amygdalina + Z. officinale (100%) was the most efficacious, while in sheep, A. cepa + C. papaya (100%), V. amygdalina + Z. officinale (100%), V. amygdalina + Z. officinale (100%) and A. comosus + N. tabacum (100%) were most efficacious. Animal species had a significant effect (P<0.001) on efficacy of combinations, efficacy was lower in goats (89.16%±0.95) relative to sheep (95.45%±0.095). Plant species did not affect (P>0.05) the efficacy of crude plant extract combinations. Vernonia amygdalina (IC50 = 0.01 mg/ml) followed by Zingiber officinale (IC50 =0.02 mg/ml) were the most cytotoxic crude extracts, while Allium cepa (IC50 = 0.27) and Aloe vanbalenii (IC50 = 0.22 mg/ml) were the least cytotoxic crude extracts. Cytotoxicity increased in a dose dependent manner. The concentration-cell viability relationship was negative linear in most crude plant extracts. While it was negative quadratic for Gunnera perpensa, Zingiber officinale and Vernonia amygdalina. Anthelmintic crude plant extracts are efficacious against GIN of sheep and goats. Although they are mostly harmless minimum effective concentration should be used. Crude plant extracts that were efficacious at the lowest concentration and observed synergistic crude plant extract combinations should be tested in vivo. Keywords: Anthelmintics, Animal species, Activity, Cytotoxic, Crude plant extract(s), Concentration, Ethno-medicinal, Gastrointestinal nematodes, Goats, In vitro, Plant species, Resistant, Sheep.