Contents lists available at ScienceDirect Veterinary Parasitology: Regional Studies and Reports journal homepage: www.elsevier.com/locate/vprsr Original article Risk factor analysis associated with Theileria equi infected equines in semi- arid and sub-humid ecological enzootic zones of India Rajesh Dahiya a,b , Raj Kumar Salar b , Kruti Debnath Mandal a,c , Rajender Kumar a , B.N. Tripathi a , Yash Pal a , Sanjay Kumar a, ⁎ a ICAR-National Research Centre on Equines, Sirsa Road, Hisar 125 001, Haryana, India b Department of Biotechnology, Chaudhary Devi Lal University, Sirsa, 125 055, Haryana, India c Division of Medicine, ICAR-Indian Veterinary Research Institute, Izatnagar 243 122, Uttra Pradesh, India ARTICLE INFO Keywords: Theileria equi Sero-prevalence India ELISA Risk factors 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 asso- ciated 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 sero- prevalence 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. 1. Introduction Ticks and tick-borne diseases have a large impact on animal health and the livelihood of livestock owners, particularly in developing countries. Equine piroplasmosis is a tick-borne disease of equids caused by Theileria equi and/or Babesia caballi protozoa. About 106 tick species have been reported from India (Ghosh et al., 2007) and ticks of genera Rhipicephalus and Hyalomma are widely prevalent in > 20 Indian states (Ghosh and Nagar, 2014). Hyalomma anatolicum anatolicum tick has been identified as the most important vector tick for transmission of T. equi infection in India, which is quite prevalent in semi-arid and sub- humid agro-ecological Indian regions (Malhotra et al., 1978; Kumar and Kumar, 2007; Bhagwan et al., 2015). T. equi infects equine erythrocytes and causes acute, sub-acute or chronic disease condition in equids (Mehlhorn and Schein, 1998). T. equi infection is responsible for important economic losses to the equine husbandry especially in tro- pical to temperate zone of the world (Asgarali et al., 2007; Acici et al., 2008). Equines chronically infected with T. equi show non-specific clinical symptoms such as fever, depression, icterus, colic and gait in- coordination, which make diagnosis of this disease condition difficult (de Waal, 1992). Clinical infection in T. equi latently infected equids is not uncommon and often associated with underlined risk factors such as host's age, immunological and concurrent disease infection status, equine farm managemental practices, etc. (Knowles Jr., 1996). Equine piroplasmosis is an OIE notifiable disease in equines (OIE, 2017). Hence serological testing of this disease is mandatory before transporting equine out of country, in order to prevent the spread of infections to naïve population. India comes under the enzootic zone for this disease condition. Therefore, it is necessary to have time to time updated information on prevalence of disease in different parts of the https://doi.org/10.1016/j.vprsr.2018.01.005 Received 17 August 2017; Received in revised form 12 December 2017; Accepted 11 January 2018 ⁎ Corresponding author at: ICAR-National Research Centre on Equines, Sirsa Road, Hisar 125 001, Haryana, India. E-mail address: sanjay.nrce@gmail.com (S. Kumar). Veterinary Parasitology: Regional Studies and Reports 12 (2018) 17–21 Available online 12 January 2018 2405-9390/ © 2018 Published by Elsevier B.V. T