Clinical impact, diagnosis and control of Equine Herpesvirus-1 infection in Europe European Food Safety Authority (EFSA (original) (raw)
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Equine Herpesvirus-1 Infection, Clinical Features, Treatment and Control
Advances in Animal and Veterinary Sciences, 2020
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 areas contaminated using disinfectants like chlorine, the quaternary ammonium compounds and the sodium linear alkylbenzene sulfonate but factors like ambient temperature, contamination by organic materials, time of exposure and disinfectant concentration should be considered.
Assessment of listing and categorisation of EHV 1 within the framework of AHL EFSA Journal
EFSA Journal, 2022
Equine Herpesvirus-1 infection has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of: Article 7 on disease profile and impacts, Article 5 on the eligibility of the disease to be listed, Article 9 for the categorisation of the disease according to disease prevention and control measures as in Annex IV and Article 8 on the list of animal species related to Equine Herpesvirus-1 infection. The assessment has been performed following a methodology composed of information collection and compilation, and expert judgement on each criterion at individual and collective level. The outcome is the median of the probability ranges provided by the experts, which indicates whether the criterion is fulfilled (66-100%) or not (0-33%), or whether there is uncertainty about fulfilment (33-66%). For the questions where no consensus was reached, the different supporting views are reported. According to the assessment performed, Equine Herpesvirus-1 infection can be considered eligible to be listed for Union intervention according to Article 5 of the Animal Health Law with 33-90% certainty. According to the criteria as in Annex IV of the AHL related to Article 9 of the AHL for the categorisation of diseases according to the level of prevention and control, it was assessed with less than 1% certainty that EHV-1 fulfils the criteria as in Section 1 (category A), 1-5% for the criteria as in Section 2 (category B), 10-66% for the criteria as in Section 3 (category C), 66-90% for the criteria as in Section 4 (category D) and 33-90% for the criteria as in Section 5 (category E). The animal species to be listed for EHV-1 infection according to Article 8(3) criteria are the species belonging to the families of Equidae,
First Report on the Frequency and Molecular Detection of Neuropathogenic EHV-1 in Turkey
Journal of Equine Veterinary Science, 2012
There has been an increase in outbreaks of neuropathogenic equine herpesvirus-1 (EHV-1) in the United States and Europe. However, the presence and frequency of neuropathogenic EHV-1 in Turkish horses are not known at present. This study aimed to investigate the frequency of EHV-1 and neuropathogenic strains of EHV-1 in the Marmara Region of Turkey. Samples were analyzed for the presence of EHV-1 and neuropathogenic EHV-1 by real-time PCR TaqMan probe assays. Overall detection rate of EHV-1 was 45.5% (51 of 112). The detection rates were 70.5% (24 of 34) in aborted fetuses, 53.3% (8 of 15) in neonatal deads, 66.6% (4 of 6) in foals, 40% (2 of 5) in dead mares, and 25% (13 of 52) in living mares. Overall detection rate of neuropathogenic EHV-1 was 7.8% (4 of 51), and the real-time PCR results were confirmed by sequencing. Neuropathogenic strains of EHV-1 were detected in the brain and lung of two mares with neurological disease but without a history of abortion, in the brain of a foal that died of respiratory disorder, and in the nasal swab from a mare with a history of abortion. On histopathology, nonpurulent meningoencephalitis, hemorrhages, and vasculitis were seen in the brain. In conclusion, results of this study indicated, for the first time, that the neuropathogenic EHV-1 is circulating in the Marmara Region of Turkey. The results of this study also show that the current risk for non-neuropathogenic strains is high, whereas risk for the neuropathogenic EHV-1-G 2254 strain seems to be low. As outbreaks of EHV-1 continue in the Marmara region of Turkey, surveillance for neuropathogenic EHV-1 genotype should be maintained.
Veterinary Record, 2003
Five of 10 pregnant, lactating mares, each with a foal at foot, developed neurological disease. Three of them became recumbent, developed complications and were euthanased; of the two that survived, one aborted an equine herpesvirus type 1 (EHV-1)-positive fetus 68 days after the first signs were observed in the index case and the other gave birth to a healthy foal on day 283 but remained ataxic and incontinent. The diagnosis of EHV-1 myeloencephalitis was supported by postmortem findings, PCR identification of the virus and by serological tests with an EHV-1 -specific ELISA. At the time of the index case, the 10 foals all had a heavy mucopurulent nasal discharge, and PCR and the ELISA were used to detect and monitor EHV-1 infection in them. The status of EHV-1 infection in the five in-contact mares was similarly monitored. Sera from three of the affected mares, taken seven days after the index case were negative or had borderline EHv-1 -specific antibody titres. In later serum samples there was an increase in the titres of EHv-1 -specific antibody in two of the affected mares. In contrast, sera from the five unaffected in-contact mares were all EHv-1 -antibody positive when they were first tested seven or 13 days after the index case.
Vaccine, 2006
Equine herpesvirus type 1 (EHV-1) is a ubiquitous alphaherpesvirus of horses which causes rhinopneumonitis, abortion and myeloencephalopathy. To test the efficacy of commercial vaccines in protection against neurological EHV-1 challenge, groups of five horses were immunized with modified-live virus or an inactivated vaccine, or received placebo. Horses were challenged by aerosol with a recent virus isolate obtained from a case of paralytic EHV-1. The duration of fever decreased significantly in the modified-live virus vaccine group. Three animals in each of the inactivate and control groups showed alterations in neurological status. When compared to the inactivated vaccine, the modified-live virus vaccine induced significantly lower virus-neutralizing antibodies over the course of the study. The modified-live virus vaccine resulted in low EHV-1-specific IgG(T)/IgGa and IgG(T)/IgGb ratios, suggesting a bias towards a cytotoxic immune response. Virus shedding from the nasopharynx was almost undetectable in the modified-live virus group, and was significantly lower when compared to that in the other groups. Normalized lymphocyte viral genome copies were similar for the three groups, although animals vaccinated with the modified-live virus vaccine were qPCR-positive on fewer days when compared to those of the other groups. Based on data from neurological signs, rectal temperatures, virus isolation from nasal swabs and immune response specificity, we concluded that protection induced by the modified-live virus vaccine is superior to that induced by the inactivated combination vaccine. (N. Osterrieder). alone licensed, to protect against the increasingly prevalent neurological signs of this worldwide-endemic virus . This conclusion is supported by recent outbreaks of paralytic EHV-1 in race horses in Kentucky, Maryland and Michigan in the USA in 2005. Lytic infection of uterine vascular endothelial cells leads to late-term abortion in mares [1], while such infection in the central nervous system (CNS) leads to reactive myeloencephalopathy . The neurological signs induced by EHV-1 range from mild ataxia to complete paraplegia requiring euthanasia of affected animals .
Viral Equine Encephalitis, a Growing Threat to the Horse Population in Europe?
Viruses, 2019
Neurological disorders represent an important sanitary and economic threat for the equine industry worldwide. Among nervous diseases, viral encephalitis is of growing concern, due to the emergence of arboviruses and to the high contagiosity of herpesvirus-infected horses. The nature, severity and duration of the clinical signs could be different depending on the etiological agent and its virulence. However, definite diagnosis generally requires the implementation of combinations of direct and/or indirect screening assays in specialized laboratories. The equine practitioner, involved in a mission of prevention and surveillance, plays an important role in the clinical diagnosis of viral encephalitis. The general management of the horse is essentially supportive, focused on controlling pain and inflammation within the central nervous system, preventing injuries and providing supportive care. Despite its high medical relevance and economic impact in the equine industry, vaccines are not...
Equine herpesviruses: a roundtable discussion
UK-Vet Equine, 2019
Foreword There are nine different equid herpesviruses (EHVs). Five types (EHV-1 to EHV-5) infect the domestic horse, while EHV-6 to EHV-9 are associated with infections in wild equids including asses and zebra. This review focuses on the commonest and most important clinical pathogens, the alphaherpesviruses EHV-1 and 4. These are respiratory pathogens and are also responsible for abortion and neurological disease. Several aspects of the biology of these viruses makes their control challenging. In particular, latent infection and reactivation of infection under stress, with subsequent virus shedding, makes elimination of these viruses impossible. Biosecurity measures are important both for minimising the risk of an outbreak and for controlling any outbreak when it occurs. Recognition of the disease and confirmatory diagnosis are also important in order for appropriate biosecurity measures to be instigated. Vaccination in key demographic groups is also important to reduce severe clin...
The Veterinary Journal, 2009
The objective of this study was to determine viral loads, strain (neuropathogenic versus non-neuropathogenic) and state (lytic, nonreplicating, latent) of equine herpesvirus-1 (EHV-1) by real-time polymerase chain reaction (PCR) in the blood and nasopharyngeal secretions of adult horses following natural exposure. The index case, a 4-year-old Thoroughbred gelding with confirmed EHV-1 myeloencephalopathy, as well as potentially exposed horses, were sampled over a period of 3 weeks. The study population comprised of 39 adult Thoroughbred horses and 35 adult ''pony'' and outrider horses of various breeds housed at a racetrack in Northern California. Blood samples and nasopharyngeal secretions (NPS) from all horses were tested on several occasions for EHV-1 DNA viral loads, targeting the glycoprotein B (gB) gene, viral strain, targeting the ORF 30 gene, and transcriptional activity of EHV-1, targeting the gB gene and latency-associated transcripts (LATs). Viral loads and transcriptional activity of the gB gene declined rapidly in the index case following antiviral treatment. The prevalence of EHV-1 infection in NPS determined by PCR slowly decreased over the 22 day study period from 25% to 14%. The initial surveillance showed multiple clusters of exposure, one associated with the index case and two related to horses that had recently returned from a different racetrack. Viral strain differentiation showed that only two horses (the index case and a neighboring horse) were infected with only a neuropathogenic strain, while all other horses were infected with either a non-neuropathogenic strain or were dually infected with both neuropathogenic and non-neuropathogenic strains. In most cases, the virus was present in either a lytic or a non-replicating form, while latent virus was found in blood and NPS much less frequently. The molecular approach used in this study showed promise for assessing the risk of exposing other horses to EHV-1 and for studying viral kinetics in infected horses.
Equine Herpesvirus-1 Consensus Statement
Journal of Veterinary Internal Medicine, 2009
Equine herpesvirus-1 is a highly prevalent and frequently pathogenic infection of equids. The most serious clinical consequences of infection are abortion and equine herpesvirus myeloencephalopathy (EHM). In recent years, there has been an apparent increase in the incidence of EHM in North America, with serious consequences for horses and the horse industry. This consensus statement draws together current knowledge in the areas of pathogenesis, strain variation, epidemiology, diagnostic testing, vaccination, outbreak prevention and control, and treatment.