A survey of plants used to treat livestock diseases in the Mnisi community, Mpumalanga, South Africa, and investigation of their antimicrobial activity

Abstract

Livestock owners in developing countries with limited access to expensive orthodox veterinary services have been using ethnoveterinary practices for animal healthcare for generations. The knowledge is passed on from generation to generation orally, but there is a concern that as time goes on the information may be lost or inadequate information may be passed on to future generations, thus there is an urgent need to document the available knowledge of ethnoveterinary medicine. The aim of this study was to document and investigate plant species that are used as ethnoveterinary medicine by the Mnisi community at Bushbuckridge in Mpumalanga Province. Following the Rapid Rural Appraisal (RRA) guidelines, a survey was conducted to document the plant species that are used as ethnoveterinary medicine within the Mnisi community. It was found that older males from the age of 40 were more knowledgeable than females and young people. Plant remedies were more frequently used than pharmaceutical drugs, with cattle being the dominantly treated animals. Eleven plant species belonging to seven families were reported by the farmers, and fresh plants from the wild were commonly used to prepare the remedies. The remedies were prepared as decoctions, infusions, pastes and extracted sap. Frequently used plants were selected and tested for their antibacterial (against planktonic and biofilm forms), antifungal, antimycobacterial and cytotoxic activity. Traditional extraction (decoctions and infusions prepared with tap water) and organic solvent extraction (extracts prepared in the laboratory using distilled water and acetone) were used to prepare the extracts which were tested against Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, Mycobacterium tuberculosis and Mycobacterium bovis. Out of all the tested samples the acetone extracts had better antibacterial activity with MIC values ranging from as low as 0.09 to 0.27 mg/ml compared to the samples extracted using traditional methods (decoctions and infusion). However, water extracts had the highest antifungal activity with MIC values ranging from 0.02 to 2.50 mg/ml compared to organic solvent extracts which had MIC values ranging from 0.63 to 2.50 mg/ml. Water extracts also had the highest antimycobacterial activity compared to acetone, with MIC values ranging from 0.02 to 1.2 mg/ml. Elephantorrhiza obliqua acetone extract had the best antibacterial activity with an MIC value of 0.09 mg/ml against P. aeruginosa, while E. obliqua water extracts had the highest antifungal activity with MIC values of 0.02 to 0.04 mg/ml against Aspergillus fumigatus. Schotia brachypetala acetone extracts inhibited Enterococcus faecalis biofilm by 113% and 135% at zero and 24 hours of bacterial growth respectively, while E. obliqua acetone extracts had values of 64% and 83% at these time periods, indicating that they were good inhibitors of biofilm formation and also had the capacity to act against mature biofilms. Seven out of nine tested plant extracts (78%) were non-toxic to moderately cytotoxic while only two plant extracts were relatively toxic against Vero cells. Aloe marlothii (infusion) and Schotia brachypetala (aqueous extract) were non-toxic with the highest IC50 values of 0.205 mg/ml and 0.105 mg/ml respectively.The selectivity index was used to relate the cytotoxicity to the antimicrobial activity of the plant extracts. Most of the plant extracts had values below 10 against all the tested microbes, implying that the biological activity of the plant extracts may be associated with toxicity. However it must be noted that toxicity in vitro might not translate to toxicity in vivo, thus in vivo studies must be carried out qualify the toxicity. In summary, plants were used in the Mnisi community for the treatment of common diseases in livestock. Only a few plant species were used, but these plant species used by the Mnisi community were related in some cases to those used in nearby areas such as the Vhembe region (Luseba and Tshisikhawe, 2013) and the Greater Giyani district (Luseba and Van der Merwe, 2006). Traditionally prepared remedies were generally more active against fungi and mycobacteria and less active against bacteria. They were also less toxic than the organic solvent extracts. However, in vivo studies are also necessary to support the traditional use of the remedies against diseases in livestock in terms of validating the efficacy but also assessing their potential toxicity.