Available online 25 March 2015
Research article
An evidence-based approach to the evaluation of ethnoveterinary medicines against strongyle nematodes of equids
Highlights
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- Nine plants were tested for in vitro anthelmintic activity against cyathostomins.
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- Plants were selected from two different countries, the UK and Ethiopia.
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- Plants were selected based on evidence of current use and supportive literature.
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- Two assays and two solvents were used to test each extract.
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- Seven plants showed significant anthelmintic activity.
Abstract
Cyathostomins
are the most important gastrointestinal nematode infecting equids.
Their effective control is currently under threat due to widespread
resistance to the broad spectrum anthelmintics licenced for use in
equids. In response to similar resistance issues in other helminths,
there has been increasing interest in alternative control strategies,
such as bioactive plant compounds derived from traditional
ethnoveterinary treatments. This study used an evidence-based approach
to evaluate the potential use of plant extracts from the UK and Ethiopia
to treat cyathostomins. Plants were shortlisted based on findings from a
literature review and additionally, in Ethiopia, the results of a
participatory rural appraisal (PRA) in the Oromia region of the country.
Systematic selection criteria were applied to both groups to identify
five Ethiopian and four UK plants for in vitro screening. These included Acacia nilotica (L.) Delile, Cucumis prophetarum L., Rumex abyssinicus Jacq., Vernonia amygdalina Delile. and Withania somnifera (L.) Dunal from Ethiopia and Allium sativum L. (garlic), Artemisia absinthium L., Chenopodium album L. and Zingiber officinale
Roscoe. (ginger) from the UK. Plant material was collected, dried and
milled prior to hydro-alcoholic extraction. Crude extracts were
dissolved in distilled water (dH2O) and dimethyl sulfoxide
(DMSO), serially diluted and screened for anthelmintic activity in the
larval migration inhibition test (LMIT) and the egg hatch test (EHT).
Repeated measures ANOVA was used to identify extracts that had a
significant effect on larval migration and/or egg hatch, compared to
non-treated controls. The median effective concentration (EC-50) for
each extract was calculated using PROBIT analysis. Of the Ethiopian
extracts A. nilotica, R. abyssinicus and C. prophetarum
showed significant anthelmintic activity. Their lowest EC-50 values
were 0.18 (Confidence interval (CI): 0.1-0.3), 1.1 (CI: 0.2-2.2) and 1.1
(CI: 0.9-1.4) mg/ml, respectively. All four UK extracts, A. sativum, C. album, Z. officinale and A. absinthium,
showed significant anthelmintic activity. Their lowest EC-50 values
were 1.1 (CI: 0.9-1.3), 2.3 (CI: 1.9-2.7) and 0.3 (CI: 0.2-0.4) mg/ml,
respectively. Extract of A. absinthium had a relatively low
efficacy and the data did not accurately fit a PROBIT model for the dose
response relationship, thus an EC-50 value was not calculated.
Differences in efficacy for each extract were noted, dependent on the
assay and solvent used, highlighting the need for a systematic approach
to the evaluation of bioactive plant compounds. This study has
identified bioactive plant extracts from the UK and Ethiopia which have
potential as anthelmintic forages or feed supplements in equids.
Keywords
- Anthelmintic resistance;
- ethnoveterinary medicine;
- bioactive plant compound;
- cyathostomins;
- in vitro assay;
- drug discovery.
Copyright © 2015 Published by Elsevier B.V.