Comparative seroprevalence and risk factor analysis of Trypanosoma evansi infection in equines from different agro-climatic zones of Punjab (India)

As parasitaemia is low and fluctuating during the chronic stage of infection, accurate detection of Trypanosoma evansi in blood is difficult. The primary aims of this investigation were to assess for the first time the seroprevalence of T evansi in all agro-climatic zones of Punjab, by indirect enzyme-linked immunosorbent assay (iELISA) and card agglutination test (CATT/T. evansi), and to evaluate the risk factors associated with latent trypanosomosis. A total of 319 equine serum samples collected from 12 districts of Punjab (India) belonging to different agro-climatic zones revealed 39 (12.23%) and 9 (2.82%) samples to be positive by CATT/T. evansi and iELISA, respectively. The highest prevalence was recorded from the Ludhiana district (42.86% and 7.14% by CATT/T. evansi and iELISA, respectively) in the central plain zone (for which the overall prevalence was 15% and 4.17%, respectively). There was fair agreement between the tests for the detection of T. evansi (kappa = 0.345). Species was the most influential risk factor for infection, with odds ratios (ORs) of 2.81 and 5.63 for donkeys/mules, in comparison with horses, by CATT/T. evansi and iELISA, respectively. The female equine population (OR = 3.13, 95% confidence interval [CI] = 1.32-7.67 [CATT]) was found to be at a higher risk of seropositivity for T. evansi, particularly on 'unorganised' (inappropriately managed) farms (OR = 3.18, 95% CI = 1.53-6.65 [CATT]) and among animals used for commercial purposes (OR = 2.51, 95% CI = 1.20-5.21 [CATT]). In conclusion, to declare disease-free status, use of the iELISA followed by retesting of suspect samples by CATT/T. evansi is suggested.