Epidemiology of tick-borne pathogens of cattle and tick control practices in coastal Kenya

Abstract

Tick-borne diseases (TBD) are a major constraint to livestock health and productivity in sub-Saharan Africa. Nonetheless, there are relatively few robust epidemiologic studies documenting TBD and its management in different endemic settings in Kenya. Therefore, a cross-sectional study using multi-stage cluster sampling was undertaken to characterize the epidemiology of TBD and management factors among zebu cattle reared under an extensive system in coastal Kenya. Blood samples from 1486 cattle from 160 herds in 14 villages were screened for the presence of tick-borne bacterial and protozoan pathogens using PCR with high-resolution melting analysis and sequencing. Standardized questionnaires were used to collect data on herd structure and herd management practices, and a mixed-effect logistic regression model to identify risk factors for tick-borne pathogens (TBPs). The application of chemical acaricide was the primary method for tick control (96.3%, 154/160), with the amidine group (mainly Triatix®, amitraz) being the most frequently used acaricides. Respondents identified East Coast fever as the most important disease and Butalex® (buparvaquone) was the most commonly administered drug in response to perceived TBD in cattle. The overall animal- and herd-level prevalence for TBPs were 24.2% (95% confidence interval (CI): 22.0-26.4%) and 75.6% (95% CI: 68.2-82.1%), respectively. Cattle were infected with Anaplasma marginale (10.9%, 95% CI: 9.4-12.6), Theileria parva (9.0%, 95% CI: 7.5-10.5), Anaplasma platys (2.6%, 95% CI: 1.9-3.6), Theileria velifera (1.1%, 95% CI: 0.7-1.8), Babesia bigemina (0.5%, 95% CI: 0.2-1.0), and Anaplasma sp. (0.1%, 95% CI: 0.0-0.4). Moreover, 21 cattle (1.4%) were co-infected with two TBPs. None of the assessed potential risk factors for the occurrence of either A. marginale or T. parva in cattle were statistically significant. The intra-herd correlation coefficients (lCCs) computed in this study were 0.29 (A. marginale) and 0.14 (T. parva). This study provides updated molecular-based information on the epidemiological status of TBPs of cattle and herd management practices in coastal Kenya. This information can be used in designing cost-effective control strategies for combating these TBD in the region.

Keywords: Anaplasma; Babesia; Ehrlichia; Kenya; Theileria; Tick-borne pathogens.