Detection of Equid Alphaherpesvirus 1 from Arabian Horses with different clinical presentations between 2016-2019 in Egypt.

Equid alphaherpesvirus 1 (EHV-1) is an important virus causing pathological disorders in horses. This highly contagious pathogen causes persistent outbreaks of upper respiratory tract infection, ocular affections, abortion, and neurological disorders with high mortality in Arabian horses in Egypt. The quick and accurate diagnosis is important to broaden our understanding about EHV-1 in the field, and to implicate stronger preventive, and control measures. Sixty-six Arabian horses from Cairo and Giza governorates were sampled from respiratory, abortigenic and neurological outbreaks over a period of 4 years. EHV-1 was diagnosed in these cases by immunohistochemistry using monoclonal antibody against EHV-1 glycoprotein B and molecular detection using gB, ORF33 specific real-time PCR. EHV-1 was detected in 25 cases, mostly from abortigenic outbreaks (14 abortions, 3 stillbirths, and two early neonatal deaths), in addition to 5 respiratory affections and single EHV-1 myeloencephalopathy. Molecular characterization revealed that the ORF33 sequences from this study were almost identical and closely related to the European EHV-1 strains. Furthermore, no difference in the amino acid sequences compared to previously published EHV-1 sequences from Egypt. The data in this study provides some insights about the prevalance of EHV-1 infection in Arabian horses, discusses EHV-1 diagnostic approaches, highlights the importance of accurate diagnosis and the importance of pregnant mare vaccination, and adds to the previous knowledge about EHV-1 in Egypt which may help in better controlling EHV-1 infections in the future.