Ethnoveterinary survey and laboratory evaluation of medicinal plants used for management of livestock respiratory and wound infections in Limpopo, South Africa

Abstract

Ethnoveterinary information has generally been poorly recorded despite its prevalent use in South Africa. The present study was initiated to quantitatively document local information on the utilization of therapeutic plants to treat livestock respiratory and dermatological infections, and to test selected extracts for biological activity. The survey was a participatory study undertaken in the Sekhukhune district of Limpopo, South Africa. Using semi-structured interviews together with questionnaires, ethnoveterinary data were collected from five farmers and thirty traditional healers. A number of diseases and associated traditional treatments were listed with the aid of local veterinarians. During the survey, it was noted that plants were traditionally used by indigenous people to treat various veterinary diseases such as pneumonia, bronchitis, tonsillitis and influenza, as well as chronic conditions like chronic obstructive pulmonary disease, wounds, boils, skin burns, abscesses, skin irritation and allergy. The plant preparations were in the majority of cases given to the livestock orally or topically, with leaves, bark and roots the most commonly used plant parts. Ethnoveterinary medicine is still extensively used among the rural farmers in the Sekhukhune district and in Limpopo in general. It was unsurprising that some medicines are used for more than one disease, most likely because they have a wide spectrum of action and are widely available. In the next step, antibacterial activities of leaves, fruits, bark, rhizome, flowers and root extracts of selected medicinal plants identified in the survey were evaluated against seven bacterial and one mycobacterial species using agar diffusion and MIC broth dilution assays. The ethanol extracts exhibited relatively higher activity against Staphylococcus aureus. Good activities were also shown by the ethanolic extract of Aloe marlothii against Mycobacterium smegmatis. Phytochemical analysis of leaf, bark, flowers, rhizome, fruit and root extracts revealed the presence of alkaloids, anthraquinones, saponins, flavonoids, phenols, glycosides, steroids, terpenoids and tannins. Phytochemical analyses indicated the presence of various bioactive constituents suggesting that the extracts of these plants can interfere with reactive oxygen species-induced oxidative stress, inflammation, and microbial growth. The occurrence of these biologically active chemicals in the plant parts may justify their wide usage in ethnoveterinary medicine. Biofilm formation is one of the critical mechanisms employed by bacteria to avoid the action of antibiotics as well as the host immune system. In the next part of the study, antibiofilm formation and mature biofilm destruction or extermination ability of acetone extracts of Bapedi ethnoveterinary combinations were tested against Staphylococcus epidermidis ATCC 35984, a known biofilm-former. The results revealed that extract combinations can prevent the formation of S. epidermidis biofilm. Respiratory infections in young animals and older animals are highly significant causes of financial losses in animal production. Such diseases are also a major cause of morbidity and mortality in humans. The improved degree of multi-drug resistant and extensively-drug resistant strains of Mycobacterium species causing tuberculosis (TB) has been worsened by the recent Covid-19 pandemic. This results in an imperative need to improve new treatments for respiratory diseases, and plants may be a source of such remedies. Activity of roots of Elephantorrhiza elephantina, leaves of Aloe marlothii, Eucalyptus camaldulensis and Euphorbia tirucalli were evaluated against microorganisms related to those causing respiratory ailments, namely Staphylococcus aureus, Pseudomonas aeruginosa, Mycobacterium smegmatis and M. bovis. These plants are used locally for the management of bovine TB and respiratory infections. The plant acetone extracts had MIC values ranging from 0.02 to 2.50 mg/ml against P. aeruginosa. The antimycobacterial MIC values ranged from 0.02 to 1.3 mg/ml. All plants had IC50 values above 0.1 mg/ml indicating that they are noncytotoxic against Vero kidney cells at the highest concentration tested. Anti-inflammatory activity of the plants was investigated using the soybean lipoxygenase inhibition assay and the activity of three plant extracts was better than that of curcumin, the positive control. Synergistic effects were exhibited against all pathogens, while antagonistic effects were not observed against any pathogens. The results support the indigenous use of these plants in the prevention and treatment of bovine TB and it is suggested that further investigation may focus on possible therapeutic use of these plants in treating TB.