Isolation and identification of equine herpesvirus -1 (EHV-1) in Egypt during 2021-2022

Equine herpes virus-1 (EHV-1) is a major cause of economic losses in horse industry all over the world especially in the Arabian countries. The aim of the study is the isolation and identification of the local equine herpesvirus-1 at northern Egypt Governorates (Cairo, Dakahlyia, Qalyubia) during 2021- 2022. A total of 50 tissue organs were collected from aborted fetuses of affected mares recently after abortion. The collected samples were screened using consensus PCR for detection of equine herpesviruses (EHVs) using specific primers targeting DNA polymerase gene which revealed that 26 out of 50 samples were positive with percentage of 52%.The molecular positive samples were subjected to conventional PCR for further molecular identification and typing of EHVs using specific primers targeting glycoprotein (gB) gene which confirmed that all amplified products were for EHV-1. Attempts for isolation of EHV-1 were performed through propagation of molecular identified samples on Madin-Darby bovine kidney (MDBK) cell line which revealed that 19 samples developed characteristic cytopathic effect in form of cell rounding and rapidly enlarging grapes like cell aggregation, and then detached of the cell, while 13 samples induced pock lesions on CAMs of SPF-ECE after inoculation for three successive passages. Serological identification of EHV-1 isolates was confirmed by immunofluorescent antibody test (IFAT) which showed that 19 samples induced intracytoplasmic greenish yellow fluorescence. Selected EHV-1 isolate was subjected for transmission electron microscopy (TEM) for demonstration of virus morphology. The obtained results confirmed that EHV-1 is the major cause of abortion among Arabian mares which disrupts breeding and showcasing events. Future considerations about management strategies together with regular and effective vaccine trials are recommended for control of EHV-1.