Study on ruminant tick infestation, phytochemical analysis and in vitro acaricidal effect of <i>Calpurnia aurea</i> and <i>Otostegia integrifolia<i> extracts on <i>Amblyomma variegatum</i>

Abstract

Ticks limit the productivity of livestock through decreased production, reproduction, increased mortality, downgrading and rejection of hides and skin. A cross-sectional study was conducted to estimate the prevalence of tick infestation in ruminant while experimental study was used to evaluate the in-vitro acaricidal efficacy of methanolic extracts: Calpurnia aurea and Otostegia integrifolia and the phytochemicals present in those extracts at different concentrations (200, 100, 50, 25, 12.5 and 6.25 mg/ml) against Amblyomma variegatum. Adult immersion was used for the in-vitro acaricidal efficacy test and plant extracts were subjected to qualitative phytochemical screening for the presence or absence of secondary metabolites using standard procedures. Out of the 160 goats, 152 sheep and 121 cattle, 23 (14.4%), 44 (28.9%) and 28 (23.1%) were found to be positive for tick infestation, respectively. The incidence of tick infestation was significantly different (p<0.01) among ruminants. Five tick spp. were identified: A. variegatum, A. gemma, R. decoloratus, R. evertsi evertsi and R. pulchellus. Extract of C. aurea and O. integrifolia was found to contain alkaloids, saponins, phlobatannin, steroids, phenolic, flavonoids, glycosides and tannins. However, both plants were found negative for triterpens. Extracts of C. aurea and O. integrifolia at 200 and 100 mg/ml concentrations showed a significantly higher (p<0.05) acaricidal activities compared to other treatments at 24 hrs post exposure. Mortality of ticks was increased with the increased dosage (concentration) and exposure time after treatment. Extracts of C. aurea showed a significantly higher (p<0.05) tick mortality (52%) compared to those of O. integrifolia (27%). This is a promising finding to have alternative means of treatment and to substitute the use of synthetic drugs which have a wide spread drug resistance especially in developing countries like Ethiopia.

Key words: Calpurnia aurea; in-vitro test; Otostegia integrifolia; Phytochemical screening; Tick infestation