Spatial sero-survey of respiratory tract viral infections in cattle at the wildlife-livestock interface in the Mnisi communal farming area of South Africa

Abstract

Animal diseases impact on livestock production and threaten food security through loss of animal protein. Additionally, disease impacts may cause major production losses by adding to the cost of livestock production through the necessity to apply costly disease control measures. Taken together, farm animal diseases have been shown to increase poverty levels particularly in poor communities in Africa that have a high dependence on livestock farming for sustenance (Perry et al., 2009). Research to learn more about animal diseases is necessary for the development of appropriate policies and strategies to prevent, control and possibly eradicate costly animal diseases in order to increase socio-economic development and improve livelihood, especially in Africa (Perry et al., 2009). The purpose of this study was to investigate five viruses that cause upper respiratory tract infections in cattle: bovine alphaherpesvirus-1 (BoHV-1), bovine viral diarrhoea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine parainfluenza-3 virus (PI-3) and bovine mastadenovirus-3 (BAV-3), in the rural Mnisi farming community in the Mpumalanga Province, South Africa which is located adjacent to the Kruger National Park (KNP) and private game reserves (Figure 1). The Mnisi Community Project (MCP) is a University of Pretoria initiative that is based on an One Health approach at the human/livestock/wildlife/ecosystem interface. Within the Mnisi community there are a number of dip tanks to which cattle are obligated to attend weekly for FMD inspection. In return, cattle are plunge-dipped free of charge in acaricides, as an aid to control tick-borne diseases such a theileriosis, anaplasmosis, heartwater and redwater. These viruses are known to cause pathology of the respiratory tract and lead to morbidity and even mortality in some cases. In addition, two of the viruses studied here, BoHV-1 and BVDV, can suppress the immune system of the host and also increase the risk of secondary bacterial infections (Valarcher & Hägglund, 2006). This study used a cross sectional design to determine the spatially explicit herd-level antibody seroprevalence of five respiratory tract viruses. A total of 423 sera stored in the Hans Hoheisen Wildlife Centre biobank were collected at 11 dip tanks in the Mnisi communal farming area. A commercially available pentavalent, indirect enzyme linked immunosorbent assay (ELISA) was performed to estimate the seroprevalence of each. The overall proportion of sera that contained antibodies against each pathogen were as follows: 43.3% for BoHV-1; 30.5% for BVDV; 82.5% for BRSV; 44.4% for PI-3 and 83.2% for BAV-3. The prevalence of antibodies against the five respiratory viruses did not appear to be influenced by location, distance from the adjacent wildlife conservation area, time of the year, or sex. However, age was a risk factor as antibodies appeared less frequently in animals less than 12 months of age compared to animals between 12 and 24 months, or older than 24 months. Findings from this study should provide information for the cattle farmers and animal health sector that provide animal health and extension services about the risk of bovine respiratory disease in the Mnisi communal farming area. Appropriate measures to minimize exposure to viral respiratory tract infections are discussed.