The prevalence of serum antibodies to East coast fever and associated risk factors in cattle in the traditional crop-livestock system in Mbeere district, Kenya; a cross-sectional study

Abstract

East coast fever (ECF) is the most important tick-borne disease (TBD) of cattle in Kenya. A cross-sectional survey was carried out in the cattle population raised under traditional crop-livestock production system in Mbeere district, Kenya. The objective was to estimate ECF seroprevalence and identify associated risk factors for planning ECF control strategies in the district. A total of 440 cattle of all ages from 80 farms were selected by multistage random sampling. Prevalence of serum antibodies to ECF was determined by enzyme-linked immunosorbent assay (ELISA). Risk factor information was collected at three levels: animal-, farm-(herd) and division-levels. The relationship between ECF seropositivity and the risk factors was assessed by multivariable analysis using logistic regression models. The overall ECF seroprevalence was 19.3% (range: 3.9% to 48% across divisions) in the district [95%CI: 13.7%, 24.9%]. Regression analysis found four major factors associated with seropositivity: presence of the vector tick on the farm (OR=3.8), frequency of calf tick control before 6 months of age (for frequency of >5 times, OR=3.9 relative to frequency of ≤5 times), herd size (OR for herd size category 6-10 cattle = 2.7; OR for over 10 cattle = 0.95 relative to herd size category 1-5 cattle) and division (ORs for Siakago, Gachoka and Mwea divisions = 0.3, 0.21 and 5.1 respectively relative to Evurore division). The low ECF seroprevalence indicates that ECF occurs in the district in an endemic instability state. The significant herd management factors possibly arose out of differential perceptions of ECF occurrence and importance across the district while the wide variation in seroprevalence across divisions was thought to be due to a gradient in vector

tick environmental suitability habitats. These findings suggest that ECF seroprevalence in Mbeere district is mainly influenced by herd and environmental factors.