Prevalence of equine gammaherpesviruses on breeding farms in Turkey and development of a TaqMan MGB real-time PCR to detect equine herpesvirus 5 (EHV-5)

Equine herpesvirus type 2 (EHV-2) and EHV-5 are members of the subfamily Gammaherpesvirinae. The viruses are detected in horses with upper respiratory tract disease and are associated with low performance in racehorses. The aim of the current study was to use nested PCR to investigate the epidemiology of EHV-2 and EHV-5 in Arabian horse populations from breeding farms located in three different cities (Eskişehir, Malatya, and Bursa) in Turkey, using a real-time quantitative PCR (qPCR) with a TaqMan® minor-groove-binder (MGB) probe to detect EHV-5. Screening of blood and ocular and nasal swab samples by nested PCR showed the prevalence of EHV-2 and EHV-5 to be 59 % and 62 %, respectively, with a coinfection rate of 45 %. Thirty-seven isolates from blood samples were identified as EHV-2 using nested PCR. To develop the EHV-5 qPCR, a pair of primers and an MGB probe were designed based on a highly conserved genomic region encoding glycoprotein B (gB). The detection limit of the qPCR was 10 molecules per reaction, and it specifically detected EHV-5 and no other herpesviruses infecting horses (EHV-1, EHV-2, or EHV-4). When applied to field samples, the assay proved to be more sensitive than a well-established nested PCR. Therefore, the qPCR developed in this study provides a rapid, reliable, and sensitive diagnostic assay for the detection of EHV-5, and it complements other diagnostic procedures for equine respiratory disease.