Molecular and serological prevalence of corridor disease (buffalo associated Theileria parva infection) in cattle populations at the livestock/game interface of KwaZulu-Natal province, South Africa

Abstract

Theileria parva are intracellular protozoal parasites responsible for three disease syndromes in cattle, namely East Coast fever (ECF), Corridor disease (CD) and Zimbabwean theileriosis. The increase in reports of CD outbreaks in recent years has raised questions about the probability of adaptation of buffalo-derived T. parva strains in cattle herds adjacent to game reserves. A cross-sectional study was conducted from March 2016 to December 2018 to investigate the extent of occurrence of T. parva infections in cattle in the CD-controlled area of KwaZulu-Natal Province. Blood samples were collected from 1137 cattle from 14 herds and analysed by quantitative real-time PCR (qPCR) and indirect fluorescent antibody test (IFAT) to determine the prevalence of T. parva. A total of 484 samples from 4 of the 14 herds were further tested on qPCR for the presence of T. taurotragi infections. The data were analysed using descriptive statistics and a chi-square test was used to assess association between variables. The overall prevalence of T. parva was 1.3% (95%CI:1-2%) and 19.9% (95%CI:17-22%) on qPCR and IFAT, respectively. The qPCR positive samples were detected in March and May while IFAT positive samples were detected in all seasons sampled, with higher numbers during summer months. The Pearson Chi-squared test showed that T. parva prevalence rates based on both qPCR and IFAT were positively associated with herds with previous history of CD outbreaks (χ² = 8.594, p = 0.003; χ² = 69.513, p < 0.001, respectively). The overall prevalence of T. taurotragi was 39.4% (95% CI: 35-44%) with the herd-level prevalence ranging between 35.0% and 43.4%. Possible cross-reaction of T. parva IFAT to T. taurotragi was detected on few samples, however, there was no significant association between T. taurotragi infections and IFAT positivity (χ² = 0.829, p = 0.363). Results from this study demonstrated the extent of occurrence of subclinical carriers and the level of exposure to T. parva infections in cattle populations at a livestock/game interface area of KwaZulu-Natal Province. The molecular and seroprevalence rates were low when compared with other areas where cattle-adapted T. parva infections are endemic. The adaptation of buffalo-derived T. parva in cattle population resulting in cattle-cattle transmissions seem to be unlikely under the current epidemiological state.

Keywords: Corridor disease; Livestock-game interface; Prevalence; South Africa; T. Taurotragi; Theileria parva.