Performances evaluation in Italian Standardbred horses PCR-positive to Theileria Equi

Purpose of the work - The aims of this study were to evaluate the prevalence of PCR positivity to Theileria equi and Babesia caballi in clinically healthy Italian Standardbred (IS) race horses, to compare the performances between PCR positive and negative horses and to investigate the possibly presence of an inflammatory myopathy causing poor performance in PCR positive horses. Materials and used methods - The study included 130 IS horses, 45 females, 85 males, from 7 stables in the Campania region (Southern Italy), aged from 3 to 11 years, that were in full training. A score was given to quantify the development of the muscles of the croup and thigh using a scale from 0 to 3, where 0 indicated the absence of atrophy, 1 mild, 2 moderate and 3 severe atrophy. Blood sampling were performed for complete blood count (CBC) and PCR for T. equi and B. caballi. To assess the performances, the number of starts, placed races, victories, best time, mean of times of the last kilometre (m/s), mean of earnings and total earnings in last 30 races prior to blood sampling were recorded. Results - 36,3% of horses were positive to T. equi. All samples were negative to B. caballi. Mares showed a higher resistance to T. equi infection than males and the prevalence was higher in older horses. The performances, haematology and serum biochemistry values did not significantly differ in positive PCR IS compared to negative ones. The gender and PCR positivity/negativity did not show any influence on performances. There is a correlation between atrophy score and stable only in Neg group horses. A moderate muscle atrophy led a decrease in performances in PCR positive horses. Conclusions - The amyotrophy highlighted in PCR positive horses, probably subsequent to an autoimmune myositis, may represent the earliest sign of losing the immune balance between host and parasite, which can be expressed with a reduction in athletic performances. Only specific diagnostic tests can allow early identification and therapy of positive horses. The use of muscle biopsies in positive horses could allow an early identification of autoimmune myositis.