Risk factor analysis associated with Theileria equi infected equines in semiarid and sub-humid ecological enzootic zones of India

Abstract

Equine piroplasmosis is a haemoprtozoan disease of equines and enzootic in tropical and subtropical countries. A cross-sectional study on sero-prevalence of Theileria equi, the causative agent of EP, was performed in semi-arid and sub-humid ecological endemic zones of India including Rajasthan, Haryana and Gujarat states, in order to evaluate the enzootic status/level of exposure to equine population due to this infection and addressed associated risk factors. Serum samples were collected from a total of 1021 equids that comprised of 792 horses, 168 donkeys and 61 mules and evaluated for T. equi specific antibodies in equine merozoite antigen-2 (EMA-2) based on indirect ELISA. The state with high sero-prevalence rate was Rajasthan (71.40%), followed by Haryana (60.39%) and Gujarat (48.92%). Overall T. equi sero-positivity in equines was 64.44%. Species-wise T. equi seroprevalence was 66.29%, 51.19% and 91.80% in horses, donkeys and mules respectively. The association and risk factor among age, gender and species in relation with T. equi infection was statistically analyzed at 95% level of significance (p < 0.05). A very high T. equi sero-positivity was recorded in 0–1 year age group of equines (60%), indicating that this naïve age group contacts with T. equi infected ticks and remains infected throughout its lifetime. The sero-prevalence rate was significantly associated with the species of animal (p < 0.05). The risk factor analysis kept mules at higher risk (Odd's ratio; 5.696; 95% confidence interval: 2.25–14.38) of getting infection as compared to horses and donkeys. This study has demonstrated high enzootic nature of T. equi infection in semi-arid and sub-humid ecological zones of India. Mules, in comparison to horses and donkeys were found at higher risk of getting T. equi infection, indicating that disease prevalence is associated with species of the infected host.