Assessment of knowledge, attitude and practices of small household farmers towards heartwater disease and molecular characterization of Ehrlichia ruminantium in Limpopo province, South Africa

Abstract

Background: Heartwater is a disease spread by ticks that is brought on by the obligatory intracellular bacterium Ehrlichia ruminantium. Heartwater disease is one of the major obstacles to livestock production as it affects many livestock animals including domesticated animals such as goats, cattle, and sheep as well as wild ruminants. In Southern Africa, it is spread by Amblyomma hebraeum ticks, and in the rest of Sub-Saharan Africa, it is spread by A. variegatum ticks. In this study, epidemiological and molecular features of Ehrlichia ruminantium in Mopani and Vhembe Districts, from ticks isolated from cattle, goats and sheep were investigated. Method: A total of 121 small household farmers from different villages in the Vhembe and Mopani Districts were recruited in the study after they have signed an informed consent. The participants were interviewed using a questionnaire to collect data related to their knowledge, attitude and practices towards heartwater disease. Ticks were collected from cattle, goats, and sheep belonging to 48 households, yielding a total of 244 ticks. Genomic Deoxyribonucleic acid was extracted from the ticks and analysed using real-time qPCR assay targeting a 226bp fragment of the PCS20 gene. Finally, a number of samples were sent for sequencing to identify different strains circulating in the region. Neighbor-joining method was used to infer phylogenetic positions on the basis of 16S rRNA gene. Results: According to the findings of the questionnaire evaluation, only about 23.1% of the participants had some knowledge of heartwater disease. Furthermore, the highest proportion of the study population (76%) associated heartwater with air-borne transmission and 77.7% of the participants failed to identify the season in which heartwater commonly occurs. About 69% of the respondents associated ticks with animal diseases while 49.6 % correctly highlighted that, ticks are disease carriers. Farmers had a positive attitude towards control and treatment of heartwater by stating that they would use prescribed medicine 23.9%, vaccines 7.4% or consulting a specialist 2.5%. Few farmers indicated that they use homemade mixtures (0.8%), dipping and spraying (0.8%) to manage animal diseases. The most preferred method of tick control used by farmers was spraying of acaricide treatment 63.6%. On account of the poor animal services reported among the visited rural communities, some farmers opted for removing ticks by hand 28.9% as their supplementary tick control method. Majority of the farmers fed their livestock at the bush 68.6% which was the most contributing factor to increased tick infestation as reported by farmers. Several plants used as medicine to treat various animal diseases were mentioned. These included: Melia azedarach, Albizia adianthifolia, Gymnosporia senegalensis, Dicerocarryum senecioides etc. The type of disease affecting the livestock mentioned by the participants was diarrhoea (43.0%) which is among the list of heartwater symptoms. The study demonstrates that respondents had inadequate knowledge about heartwater disease. Animal services need to be upgraded in order to help the farmers improve the quality of their produce. The results of the PCR test showed that 56.2% of the household farms had E. ruminantium infection. The distribution of E. ruminantium by source of ticks and animal type revealed that cattle are more prone to tick distribution 43.5% as compared to other animal sources of ticks. Nzhelele municipality had the highest prevalence of E. ruminantium (37.0%) compared to the other municipalities. Prevalence of E. ruminantium by gender of farmers was found to be high from males 36.7% than females 25.0%. Farmers with household income > R20000 had the highest prevalence of E. ruminantium (50.0%) than farmers with household income < R500, (14.3%). The age of the farmers 15 – 20 years old revealed the highest prevalence 46.7 % of E. ruminantium infection. However, there were no infection among the ticks obtained from animals belonging to farmers above 60 years old. Farmers who had tertiary level of education showed the highest prevalence 46.8% probably because of limited time to attend to their livestock. Many clades were identified by phylogenetic analysis of the E. ruminantium PCS20 genotypes. Conclusion: This study showed that there is need to further educate small farmers on heartwater disease. It also showed that indigenous knowledge still contributes significantly to the management of animal diseases in most rural communities. The application of real time PCR showed a high prevalence of E. ruminantium infected A. hebraeum ticks from livestock and should be considered in the continuous monitoring of the animal population in order to avoid heartwater disease outbreak in the communities which could be detrimental for the local economy. Furthermore, future vaccine development against E. ruminantium should consider the diversity observed in the present study. That could be helpful in managing heartwater disease in the areas that were investigated.