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

Abstract

Ethnoveterinary medicine (EVM), although not documented well, still serves as an alternative or complementary medication for curing or preventing bacterial, fungal and helminth diseases, as well as other maladies such as ticks and tick-borne diseases in South Africa. The aim of this study was to document plant species used as EVM by the Mnisi community at Bushbuckridge in the province of Mpumalanga, and to evaluate their antimicrobial, antibiofilm and cytotoxic activities. The survey was carried out for two weeks from the end of January to the beginning of February 2018 at the local dipping tanks following the Rapid Rural Appraisal (RRA) approach. A total of 50 individuals were interviewed: 82% were local small scale farmers, 10% were herdsmen, 6% herbalists and 2% animal health technicians. Three plant species were selected for bioassays based on their frequency index and lack of information on their bioactivity in the literature. Traditional methods were used for plant extraction using water as described by the respondents. Acetone was used as an organic solvent to compare traditional and organic solvent methods of extract preparation. The extracts were tested for their antibacterial, antibiofilm, antifungal, and cytotoxic properties.

Eleven plant species belonging to seven families were reported by the farmers for EVM use, and fresh plants from the wild were commonly used to prepare the remedies as decoctions, infusions, pastes and extracted sap. Elephantorrhiza obliqua acetone extract had the best antibacterial activity with a minimum inhibitory concentration (MIC) value of 0.09 mg/mL against Pseudomonas aeruginosa, while E. obliqua water extracts had the best antifungal activity with MIC values of 0.02 to 0.04 mg/mL against Aspergillus fumigatus. Schotia brachypetala acetone extracts inhibited Enterococcus faecalis biofilms by 113% and 135% at zero and 24 h 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. Traditionally prepared remedies were generally more active against fungi and mycobacteria and less toxic than the organic solvent extracts. However, in vivo studies are 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.