Comparison of PCR-based methods for the detection of Babesia caballi and Theileria equi in field samples collected in Central Italy

Equine piroplasmosis (EP) is a disease of equids caused by Theileria equi and Babesia caballi, members of the order Piroplasmida, transmitted by several species of ticks. As the disease is endemic in many countries, a clinical examination or a serological test are required prior to movement of horses to prove freedom from infection and to avoid the introduction of EP with its sanitary and economic impact, especially in areas where it is absent. Currently, numerous diagnostic PCR protocols are available, some of which are recommended by the World Organisation for Animal Health (OIE). In order to adopt this diagnostic method, the Italian National Reference Centre for Equine Diseases (NRC-ED) conducted a preliminary comparison between an end-point PCR, nested PCR, real-time PCR, and commercial real-time PCR, for the detection of T. equi and B. caballi, respectively. One hundred and three field samples, collected during spring-summer 2013 in Latium and Tuscany regions, were employed for the study, and results discordant between detection assays were confirmed by sequencing. The reference assay was defined as that showing the highest sensitivity, and the relative sensitivity (rSe) and specificity (rSp) of the other methods were estimated referring to this assay. Agreement between methods was estimated by calculating the concordance between each pair of methods. Although no statistical differences were detected among PCR-based methods, the non-commercial real-time PCR assays seemed to be the most suitable for detection of T. equi and B. caballi, respectively. An important advantage of direct PCR detection of the pathogen, in comparison to indirect detection using serological methods, is that it allows specific treatment against the causative pathogen species responsible of the infection as well as for the definition of the infectious status of an animal for international movement.