An Ethnobotanical, Phytochemical, toxicity and efficacy study of selected antiblue-tick (boophilus decoloratus) herbal remedies for cattle of Suba sub-county, Kenya

Abstract

The search for safe pest control options has led to the exploration of potential plants with pesticidal activity. Plants have been reported to exhibit a wide range of biological activities against insect pests, some of which have been validated. Recently, attention has focused on the identification of compounds present in plants with acaricidal properties since blue-tick has remained an economic threat to most smallholder livestock farmers in rural areas in Kenya. Numerous ethnoveterinary practices are harmful, remedies not standardized and dosages are uncertain. Therefore this research investigated the ethnobotany, phytochemistry, toxicity and acaricidal activity crude extracts of three selected plants against blue-tick in Suba Sub-County. A total of 32 herbalists aged between 28 to 87 from four villages were interviewed by use of a questionnaire about their knowledge of acaricidal plants in Suba Sub-County. The local name, part used, traditional mode of preparation and method of administration were documented. There was a high correlation between the age of informants and the number of medicinal plant citations. The study identified 16 plants distributed among 13 families based on independent reports (IR). Phytolacca dodecandra, Cissus quadrangularis and Ipomoea kituiensis were collected, extracted in methanol in dichloromethane (1:1 v/v) and separately in distilled water for phytochemical studies. Phytochemistry focused on terpenoids, tannins, saponins, flavonoids and alkaloids where all were present in the three plants except flavonoids which were absent in P.dodecandra. The in vitro acaricidal activity study of crude extracts of these selected plants was done using larvae of Boophilus spp. tick to assess their potency. Using 2.5, 5 and 10 mg/mL concentrations of water and methanol in DCM (1:1 v/v) crude extracts of Phytolacca dodecandra (leaves), Cissus quadrangularis (whole) and Ipomoea kituiensis (leaves), their effects were compared with that produced by the standard reference acaricide, almatix® ( 12.5 % amitraz) as positive control. The activity of the extracts were tested against the larvae and at 10 mg/mL concentration, the extracts were most active. Mortality was determined within duration of 24 hours. The most potent extract as compared to almatix were Cissus quadrangularis (100 kills at 10 mg/mL) and Phytolacca dodecandra (100 kills at concentrations, 5 and 10 mg/mL) while Ipomoea kituiensis methanol/DCM (1:1v/v) extract was least potent. Analysis of variance revealed that there were significant differences in acaricidal activity of plants’ extracts of all the concentrations used (2.5, 5 and 10 mg/mL) (P≤0.05). B.decoloratus larvae’s LC50 was determined where methanol: DCM (1:1 v/v) extract of I. kituiensis displayed mild toxicity while those of P. dodecandra and C. quadrangularis recorded high toxicity. The conclusion from this study is that C.quadrangularis (whole), I.kituiensis (leaves) and P.dodecandra (leaves) extracts are acaricidal and are as potent at high concentrations as compared to almatix. The mortalities of the larvae increase with increase in concentration of extract and thus the leading three study plants’ extracts are effective in blue-tick control. To achieve highly efficacious traditional acaricides, it is recommended that isolation and purification of the crude compounds and bioassay of these isolated compounds be done on the same blue-tick larvae.