Equine trypanosomosis in central and western Punjab: Prevalence, haemato-biochemical response and associated risk factors

The detection of Trypanosoma evansi in blood is intricate, primarily in chronic stage of infection, as the parasitaemia is often low and fluctuating. The climatic conditions of the target area of Punjab (a province of India with a total of 34,000 horses and ponies used for sports and transport) are conducive for the parasite propagation. The objective of present investigation was to assess the prevalence of T. evansi in central and western Punjab by PCR and card agglutination test (CATT/T. evansi) in relation to clinico-haematobiochemical alterations and risk factors associated with latent trypanosomosis. A total of 169 equine blood and serum samples tested by CATT/T. evansi revealed 16 cases positive, with 6.8% from central plain and 13.63% from western zone. To assess the specificity of serological test, PCR1 was performed using established primer pair TR3 5′-GCG CGG ATT CTT TGC AGA CGA-3′ and TR4 5′-TGC AGA CAC TGG AAT GTT ACT-3′ for T. evansi. PCR2 applied with primer pair RoTat1.2F: 5′-ATG TCA ACG ATG CCT GTT ACA TTA CGC AC-3′ and RoTat1.2R: 5′-TAA ATA TCA CTG TCA AGA CCT GCT GCG G-3′ to rule out the consensus between the finding of the two PCR assays and agglutination test for T. evansi, which displayed results in concordance with PCR1. PCR assays showed 1.92 and 1.51% positive samples from central plain and western zone, respectively. With respect to PCR assay, CATT/T. evansi showed 100% sensitivity and 92.1% specificity. Microscopy showed a very low prevalence rate of 0.59% with only one sample positive with teaming parasitaemia. Comparison between sexes revealed higher positivity in mares by the three tests (BSE: 0.95%, PCR: 2.88%, CATT/T. evansi: 14.42%). The haemato-biochemical factors were found to be altered in PCR positive cases, while the mean value of vital parameters lied in normal range in seropositive cases. The female horse (RR = 0.0937, 95% CI = 1.388–190.223%) population was found to be at the highest risk of seropositivity for T. evansi, particularly in the unorganized farms (RR = 19.726, 95% CI = 2.918–400.221%).