Prevalence of equine herpesvirus type 1 latency detected by polymerase chain reaction

In this study, an improved polymerase chain reaction (PCR) was used for det ection of DNA of latent EHV-1 strains from several sources. Three pairs of oligonucleotide primers spanning fragments of 333 bp, 226 bp and 268 bp of the thymidine kinase (tk) gene, and one primer pair spanning 225 bp of the glycoprotein C (gC) gene were used in specific amplifications. Primers for EHV-4 PCR were also designed. Restriction digests with TaqI confirmed the i dentity of tk PCR fragments from EHV-1. The sensitivity to detect PCR produ cts was further improved by visualisation in silver-stained acrylamide gels . PCR assays were applied to 267 samples including pools of tissue, periphe ral blood leukocytes (PBL) and nasal swabs of archived, farms and abattoir specimens from a total of 116 animals. The EHV-1 DNA was found in 88% of th e analysed samples. The prevalence of the EHV-1 latent or persistent form i n adult horses was similar to others reports but found higher than previous ly described in foetuses and young foals. EHV-4 latency was not detected in the Brazilian studied specimens.