Spatio-temporal analysis of bovine theileriosis (Theileria parva) in Zimbabwe from 1995 to 2018

Abstract

Bovine theileriosis is a serious veterinary challenge that is responsible for high cattle mortalities and thus limiting cattle production and improvement in the smallholder farming sector of Zimbabwe (Lawrence, 1994). Despite its huge impact on the cattle industry, the spatial and temporal distribution dynamics of bovine theileriosis in the country remain scant and outdated. A retrospective study was therefore conducted to investigate the spatial and temporal patterns of bovine theileriosis in Zimbabwe in the period 1995 to 2018 to improve understanding of the disease’s dynamics. It was hypothesised that spatial and temporal patterns of bovine theileriosis in Zimbabwe were unchanged during this period. Data on bovine theileriosis cases were obtained from the Department of Livestock and Veterinary Services of Zimbabwe (DLVSZ) bovine theileriosis database for the period 1995 to 2018. The data were collated in Microsoft Excel and analysed using SatScan® version 9.4.6 for spatio-temporal clustering so as to detect high-risk areas for bovine theileriosis and Studio R® version 11.0 for evaluation of potential risk factors associated with disease occurrence.

A total of 4 540 deaths and 8 728 cases of bovine theileriosis were recorded during the study period (1995 – 2018). Adult cattle (2 496; 29%), the hot wet season (3 627; 42%) and communal areas (6266; 72%) had the highest number of cases recorded. One-year and one-month aggregates detected five and four high risk clusters of bovine theileriosis respectively, all within the last seven years of the study period (2011 – 2018). The multivariate model detected all the six tested variables (province, sex, farming system, season, year and age) to be associated with bovine theileriosis occurrence (P < 0.2) in the univariate model. The hypothesis that spatial and temporal patterns of bovine theileriosis were constant from year to year between 1995 and 2018 in Zimbabwe was rejected as it was shown that the spatial and temporal patterns of Zimbabwe bovine theileriosis were not the same over the study period. The results showed bovine theileriosis cases in relation to the identified potential risk factors, risk areas and risk clusters over time and space and thus, the null hypothesis was rejected. Findings support the fact that there is proliferation of bovine theileriosis during the hot wet season, especially in the communal grazing areas. Recommendations for control and prevention strategies especially in high-risk areas and seasons revolve around better farmer awareness and improved knowledge about the disease, correct and consistent use of acaricides, cattle immunization with the correct vaccine, cattle movement control and improved disease surveillance.