Molecular Detection and Genetic Characteristics of Equine Herpesviruses 1 and 4 in Egypt.

The present study investigated the molecular detection and genetic characteristics of equine herpesvirus 1 (EHV-1) and EHV-4 circulating within Egyptian horse populations during 2019-2022. A total of 79 animals were sampled (54 nasal swabs and 25 aborted fetal tissues). PCR assays revealed that 24 (30.3%) and 7 (8.8%) samples were positive for EHV-1 and EHV-4, respectively. Additionally, 5 (6.3%) samples were concurrently infected with both viruses. Four EHV-1 and three EHV-4 isolates were genetically characterized based on partial sequencing of gB gene. The four EHV-1 strains displayed 100% nucleotide identity to one another and to EHV-1 reference strains reported in Egypt and other countries. The three EHV-4 strains were phylogenetically classified into two distinct clusters based on their nucleotide sequences (76%-100% identity). Meanwhile, their deduced amino acid sequences differed by only one amino acid substitution. Our results underscore the critical importance of EHV-1 and EHV-4 as primary contributors of abortion and respiratory illness in horses and highlight the need for further large-scale surveillance and in-depth characterization studies to improve our understanding of these viruses' epidemiology in Egypt and to develop a robust control strategy.