Laboratory-based longitudinal surveillance of malignant catarrhal fever in Lephalale municipality in Limpopo province, South Africa: 2001-2021

Malignant catarrhal fever (MCF) is a fatal viral disease of domestic cattle, but pigs, buffaloes, bison and deer have also been reported to be affected by this disease. MCF is caused by alcelaphine herpesvirus 1 (AlHV-1) which is primarily carried and transmitted by wildebeest. It is also caused by the ovine herpesvirus 2 (OvHV-2) which is commonly carried and transmitted by sheep. In South Africa, the wildebeest-associated MCF form is prevalent and has serious economic and animal welfare impact for cattle farmers located close to farms and ranches where wildebeest are kept. However, the occurrence of MCF and its contribution to cattle mortalities has been poorly studied in livestock farms in the Lephalale municipality of Limpopo province where cattle and wildebeest cohabit. The aim of this study was to provide laboratory-based surveillance data that describes the occurrence of MCF in the Lephalale municipality for the period spanning 2001 to 2021. Laboratory registry data for 385 samples were analysed. The data included the date of sampling, sample type, animal species, location and the MCF test result (PCR and/or histopathology). Altogether, 57.4% (n = 221) of the samples were positive with a frequency of detection of 86.4% (n = 191) and 13.6% (n = 30) for samples tested using PCR and histopathology respectively. Of the PCR-positive samples, 99.5% were positive for AIHV-1 and 0.5% for OvHV-2. AIHV-1 infection was recorded during various seasons throughout the two decades while OvHV-2 was only reported in spring of the year 2010. Moreover, AIHV-1 was detected with a high frequency in blood (66.5%), brain (22.5%) and organ (10.5%) samples from different areas within the municipality, while OvHV-2 was only detected in blood (0.5%) samples. A retrospective study such as this provides useful information on the occurrence of MCF in the Lephalale municipality. Data from this study suggests that MCF caused by AIHV-1 is regularly diagnosed in the Lephalale municipality with concomitant adverse effects on the cattle population. Therefore, there is a need to formulate policies and strategies for disease control and enhance farmer education on the epidemiology of the disease within the study area to improve animal health and production.