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).

This research investigates the frequency of different genotypes of equine herpesvirus-1 (EHV-1) in horses with various conditions in the United States from 2019 to 2022. The study suggests that genotype N was the most prevalent, while a new genotype H was confined to specific outbreaks and showed no widespread incidence during this period.

Background and Objectives of the Study

• The research sought to collect contemporary data on equine herpesvirus-1 (EHV-1) genotypes and their association with disease expression.
• Identifying the frequency of different EHV-1 genotypes (non-neuropathogenic or N, neuropathogenic or D and new variant or H) in clinically ill horses is crucial.
• This could aid in diagnosis, help establish appropriate medical interventions, and develop preventive protocols to mitigate the severe complications associated with EHV-1 infection.

Methodology

• A total of 297 EHV-1 qPCR-positive swabs collected from 2019 to 2022 from horses suffering from respiratory disease, neurological disease (EHM), and abortion, were tested for the three known EHV-1 genotypes.
• These samples originated from the United States and included 257 EHV-1 cases, 35 EHM cases and 5 cases of abortion.
• The qPCR allelic discrimination assays were used to detect the different EHV-1 genotypes in the samples.

Findings

• It was found that N was the predominant genotype detected in EHV-1 cases (87.5%), EHM cases (74.3%) and abortions (80%).
• Genotype D was detected less frequently in EHV-1 cases (9.3%) and EHM cases (25.7%).
• Genotype H was only detected in EHV-1 cases and represented just 3.1% of the cases.
• The research also found seasonality in EHV-1 qPCR-positive cases, which were predominantly seen during winter and spring.

Conclusions and Implications

• The N genotype, while being the predominant genotype causing respiratory disease and abortion, has also now emerged as a leading genotype in cases of EHM.
• A new H genotype first reported in the United States in 2021 has remained constrained to a cluster of outbreaks that were geographically and temporally related.
• The data presented no evidence of an emerging spread of the H genotype since its first report.
• The research emphasizes the importance of monitoring EHV-1 genotypes for both diagnostic purposes and from an epidemiological standpoint.