The evaluation of African and UK bioactive plant extracts for the control of equid gastrointestinal nematodes
In the developed world the control of equid gastrointestinal (GI) nematodes, in particular cyathostomins, is increasingly challenging due the threat of anthelmintic resistance. In developing countries such as Ethiopia despite high parasite burdens, access to genuine anthelmintic treatment is limited. In both situations there is a need for alternative treatment and management regimens for effective parasite control and consequently there has been increasing interest in the use of bioactive plant extracts (BPEs) . This study identified candidate plants in the UK and Ethiopia and evaluated their in vitro efficacy against cyathostomin populations derived from donkeys. A participatory rural appraisal (PRA) approach was used to identify five ethnoveterinary medicines for use in donkeys in Ethiopia. In the UK three plants were identified following extensive review of literature citing efficacy against GI nematodes of other host species and two extracts were provided courtesy of Prof Jerzy Behnke, University of Nottingham. Hydro-alcoholic extraction of dried plant material was carried out for the eight extracts prior to reconstitution in both water and DMSO. Efficacy of each extract was evaluated by egg hatch assay (EHA) and larval migration assay (LMA) using eggs and larvae recovered from the faeces of donkeys at the Donkey Sanctuary, UK. Dose response curves were produced and ED-50 values were calculated using probit analysis. Of the five Ethiopian plant extracts tested, four showed efficacy in the EHA and/or LMA. The two most efficacious were Acacia nilotica and Rumex abyssinicus in the EHA with ED-50 values of 0.72mg/ml and 1.29mg/ml respectively. Of the five UK extracts four showed efficacy in the EHA and/or LMA. The two most efficacious were Carica papaya (papaya) in the LMA and Allium sativum (garlic) in the EHA with ED-50 values of 18.9µM and 0.65mg/ml respectively. The two BPEs most efficacious in vivo for Ethiopia and the UK are to be carried forward to in vivo trials. This study has demonstrated in vitro efficacy of nine plant extracts against cyathostomins. There is evidence in the literature that these plant extracts show efficacy both in vitro and in vivo against GI nematodes in other species. Therefore these results have identified potential alternatives to synthetic anthelmintics for the treatment of cyathostomins that require further investigation.  Githiori JB, Athanasiadou S, Thamsborg SM. Use of plants in novel approaches for control of gastrointestinal helminths in livestock with emphasis on small ruminants. Vet Para 2006;139, 308–320.