A nested PCR for the detection and differentiation of EHV-1 and EHV-4

The nested PCR method was applied for the detection and direct differentiation of equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4). Primer pairs were chosen from the glycoprotein B (gB) coding region of each serotype. The outer and inner EHV-1 primer pairs were type-specific, whereas the outer EHV-4 primer pair amplified EHV-1 and EHV-4 DNA and was therefore suitable for the detection of both virus types in a single sample. However, the nested EHV-4 primer pair was type-specific. The advantages of the nested PCR are twofold. Firstly, this assay was in the case of EHV-1 100 times, and in the case of EHV-4 1000 times more sensitive than the standard PCR, which indicates a detection limit of 1-0.1 fg of DNA (3-1 genome equivalents). Secondly, it allows the direct differentiation of EHV-1 and -4 without the need to resort to further analytical techniques.