Equine Herpesvirus-1 Infection, Clinical Features, Treatment and Control

Abstract

E quine herpesvirus type-1 (EHV-1) is Equine herpesvirus type-1 (EHV-1) is belong to the family Herpesviridae, subfamily alphaherpesvirinae, genus Varicellovirus, and species Equid alphaherpesvirus 1. It is a ubiquitous and highly contagious pathogen that causes a range of disease severities with outbreaks of notable economic impact (Ata et al.,2 018a, b; Tallmadge et al., 2018). It is a serious worldwide threaten to the horse industry (Lunn et al., 2009). The output of this disease includes one or more of the following clinical signs; severe respiratory manifestations, abortion storm in mares, neurological signs or even death (Walter et al., 2013; Damiani et al., 2014; Ata et al., 2018b). Inhalation of the virus infectious particle to the respiratory tract is the main route of infection, the initial replication of the virus occurs at the upper respiratory tract results in virus shedding in the nasal discharge (Kydd et al., 1994). Fever and respiratory clinical signs may appear, although some horses express subclinical shedding (Burgess et al., 2012). Within the first two weeks of infection, the clinical respiratory signs usually cease but returning of the lymph review Article Abstract | Equine herpesvirus type 1 (EHV-1) is a worldwide threaten affects the equine industry. The clinical features of EHV-1 infection included the respiratory, abortion, neonatal disease, and neurological forms with a frequently fatal outcome especially in the old age cases. The respiratory form characterized by fever, anorexia and nasal discharges. The abortion could occur in the last third of pregnancy either sporadically or progress into a storm. While in the case of myelencephalopathy, the signs ranged from mild ataxia to severe neurological deficits. Treatment of such cases depends on decreasing the inflammatory signs through using symptomatic and supportive treatment. So, a combination of free-radical scavengers, anticoagulants, and anti-inflammatory drugs, specific anti-herpesvirus drugs (e.g. acyclovir and valacyclovir) especially with the injection route rather the oral one are recommended. Because of the ubiquitous nature of the EHV-1 and the establishment of lifelong latency, elimination of the pathogen from the equine population is difficult. EHV-1 infection results in short-lived immunity which does not prevent re-infection. Although the modified live virus (MLV) and inactivated vaccines are available, it was shown to suppress EHV-1 disease not to limit the viral load. The MLV vaccines have an excellent safety record and can protect horses against clinical disease; however, their efficacy in preventing viremia, abortion, and neurological disease is unclear. Early diagnosis, prevention of further spread and management of clinical cases are the major priorities to control an outbreak. Prevention of virus spreading can be relatively achieved through sound biosecurity measures. This entails quarantine and isolation of new additions for at least a month, cleaning and disinfection of transportation equipment, fomites, and the ar...

Role of evolutionary epidemiology in the determination of the risk factors associated with some equine viral diseases

“…The EHV-1 disease was more prevalent in young horses less than 3 years, but older horses are likely to be sub-clinically infected (26). Infection with EHV-2 and EHV-5 was common in young horses in comparing with the old ones, a different study cleared those horses > 5 years of age were at significant risk of getting EHV-1 infection in comparison with those < 1-year-old (2).…”

“…It is a non-replicative, non-immunogenic stage and one of the main EHV-1 infection criteria, by which the genome is maintained in the trigeminal ganglia or in lymphoid tissues, without expression of structural genes and without production of infectious viruses (2,7). The latently infected cells are not recognised by the host immune system, these animals are the keys importance in the epidemiology of EHV-1 as they are a source of infectious virus to other susceptible animals and many sporadic cases of abortion and encephalomyelitis happened due to reactivation of the virus within the blood vessels of the pregnant uterus or the central nervous system (57).…”

“…So, any infectious threat happens not only affects the endemic areas but also affects other regions at risk of epidemics from importation. Emerging viral diseases outbreaks have grown rapidly in the recent years and a great impact on human life was recorded (1,2). Tran's boundary animal diseases have a great potentiality to threaten food security, through serious loss of animals, and increasing poverty levels.…”

Epidemiological aspects of some equine viral diseases

“…They have extended their geographic distribution and emerged in new regions of the world (3)(4)(5)(6). Many diseases were underestimated due to using of serological methods as it more available and easier to practice (7)(8)(9). But, in the recent decades, molecular detection and phylogeny become so important in monitoring the spreading (10,11).…”

“…It has a significant economic effect on the equine industry due to its worldwide distribution adding to the obligatory elimination of infected cases (18). The Equine herpes viruses are the most important equine disease not only for their wide spread, but also due to their responsibility for causing different clinical forms adding to developing a latent infection status which prevents complete control of the disease (4,7). Not all available vaccines provide complete protection against abortion or even viremia (19).…”