EHV-1: A Constant Threat to the Horse Industry

Abstract

Equine herpesvirus-1 (EHV-1) is one of the most important and prevalent viral pathogens of horses and a major threat to the equine industry throughout most of the world. EHV-1 primarily causes respiratory disease but viral spread to distant organs enables the development of more severe sequelae; abortion and neurologic disease. The virus can also undergo latency during which viral genes are minimally expressed, and reactivate to produce lytic infection at any time. Recently, there has been a trend of increasing numbers of outbreaks of a devastating form of EHV-1, equine herpesviral myeloencephalopathy. This review presents detailed information on EHV-1, from the discovery of the virus to latest developments on treatment and control of the diseases it causes. We also provide updates on recent EHV-1 research with particular emphasis on viral biology which enables pathogenesis in the natural host. The information presented herein will be useful in understanding EHV-1 and formulating policies that would help limit the spread of EHV-1 within horse populations.

Transcriptomic Profiling of Equine and Viral Genes in Peripheral Blood Mononuclear Cells in Horses during Equine Herpesvirus 1 Infection

“…Latent infections are typically subclinical, though reactivation or reinfection from another host can produce active clinical disease. In horses, the most commonly described herpesviruses include Equid alphaherpesvirus 1 (EHV-1), Equid gammaherpesvirus 2 (EHV-2), Equid alphaherpesvirus 4 (EHV-4), and Equid gammaherpesvirus 5 (EHV-5) [ 2 ]. These viruses fall into two main subfamilies: Alphaherpesvirinae (EHV-1 and EHV-4) and Gammaherpesvirinae (EHV-2 and EHV-5).…”

“…These viruses fall into two main subfamilies: Alphaherpesvirinae (EHV-1 and EHV-4) and Gammaherpesvirinae (EHV-2 and EHV-5). Alphaherpesviruses are known for their rapid lytic replication in many cell types [ 2 ]. Alphaherpesviruses typically (though not exclusively) establish latency in the sensory ganglia of their host; however, EHV-1 is also known to establish latency in lymphoid tissues [ 3 , 4 , 5 , 6 , 7 ].…”

Viral Equine Encephalitis, a Growing Threat to the Horse Population in Europe?

“…Virus: EHV-1 and 4 are members of the Varicellovirus genus, in the Alphaherpesvirinae sub-family in the family Herpesviridae (Figure 1). These alphaherpesviruses are characterized by lytic infection and can establish a lifelong latent infection in blood circulating and lymph node-residing lymphocytes, as well as in sensory neurons within the trigeminal ganglia, which may reactivate upon stress [27,28]. The linear double-stranded DNA genome of EHV-1 contains 80 open reading frames and is 150 kb long and consists of a unique long (UL) and unique short region (US) [29].…”

“…EHV-1 outbreaks have been reported for centuries and many cases are reported across Europe, in France, Great Britain and Belgium, in the United States, in New-Zealand, Australia, Chile, Argentina, Israel and United Arab Emirates [31][32][33]. EHM incidence has increased in most parts of the world, in Europe and North America, as well as in Oceania, Africa, and Asia [10,11,28]. Pathogenesis and clinical disease: After primary replication in the respiratory tract, EHV-1 disseminates via cell-associated viremia in peripheral blood mononuclear cells and subsequently infects the endothelial cells of the pregnant uterus or central nervous system, leading in some cases to abortion and/or neurological disorders [34].…”

Special Issue “Equine Viruses”: Old “Friends” and New Foes?

“…This disease, caused by the orbivirus AHS virus (AHSV), induces a very high mortality rate that can exceed 95% in its most severe form. The equine herpesvirus type 1 (EHV-1) is of particular interest to the equine industry because of the different forms of disease it can induce, from a mild respiratory infection to abortion, neonatal death, and myeloencephalopathy (EHM) [3]. In the absence of treatment, prevention is essential, and Dennis et al also provide a comprehensive review of the different vaccine strategies and technologies available and in current development against AHSV.…”