Investigation of the EHV-1 Genotype (N752, D752, and H752) in Swabs Collected From Equids With Respiratory and Neurological Disease and Abortion From the United States (2019-2022).

ABSTRACT

Contemporary data on equine herpesvirus-1 (EHV-1) genotype (non-neuropathogenic or N752, neuropathogenic or D752 and new variant or H752) in clinically diseased equids is important in order to determine the frequency of these genotypes and their association with disease expression. A total of 297 EHV-1 qPCR-positive swabs collected from 2019 to 2022 from horses with respiratory disease (EHV-1), neurological disease (equine herpesvirus-1 myeloencephalopathy [EHM]) and abortion were tested for the three different EHV-1 genotypes (N752, D752 and H752) using qPCR allelic discrimination assays. All submissions originated from the United States and included 257 EHV-1 cases, 35 EHM cases and 5 cases of abortion. EHV-1 qPCR-positive cases were predominantly seen during winter and spring. N752 was the predominant genotype detected in EHV-1 cases (87.5%), EHM cases (74.3%) and abortions (80%). D752 was detected less frequently in EHV-1 cases (9.3%) and EHM cases (25.7%), while H752 was only detected in EHV-1 cases (3.1%). While the N752 genotype has remained the predominant genotype affecting horses with respiratory disease and abortion, it has also become a leading genotype in cases of EHM, when compared to historical data. The new H752 genotype, first reported in the United States in 2021, has remained confined to a cluster of geographically and temporally related outbreaks and the data showed no emerging spread of H752 since it was first reported. While the monitoring of EHV-1 genotypes is important from a diagnostic and epidemiological standpoint, it may also help establish medical interventions and preventive protocols to reduce the risk of severe complications associated with EHV-1 infection.