Equis ISSN 2398-2977
Respiratory: EHV infection
Synonym(s): EHV-1, EHV-4
Contributor(s): Sarah Binns, Christopher Brown, Rachael Conwell, Timothy Mair
Introduction
- Five equine herpesviruses Equine herpesvirus have been identified, each with a different clinical presentation; EHV-1, 2, 3, 4 and 5.
- Cause: rhinopneumonitis.
- Signs: pyrexia, depression serous → mucopurulent nasal discharge; rarely secondary bacterial bronchopneumonia.
- Diagnosis: virus isolation; serology; histopathology.
- Treatment: control secondary bacterial infection; quarantine newly introduced or stressed animals; vaccination.
- See also Abortion: EHV 1 Abortion: EHV-1 , CNS: myeloencephalopathy CNS: myeloencephalopathy - EHV , Lung: multinodular fibrosis Lung: multinodular fibrosis .
- Prognosis: good.
Print off the Owner factsheet on Equine herpesvirus - EHV to give to your clients.
Pathogenesis
Etiology
Predisposing factors
General
- Young age.
- Stress.
- Season (autumn/winter).
Specific
- Waning maternally derived immunity.
- Reactivation of latent infection.
Pathophysiology
- Spread by close contact or aerosol transmission → primary replication, usually in respiratory epithelium → viremia → localization in predilection site, eg lymphoid tissue, epithelium → latent infections may develop in neural or lymphoid tissues → recrudescence under conditions of stress.
EHV-1
- Replication in respiratory tract → viremia → respiratory tract infection.
- Damage to endothelium of central nervous system vasculature → myeloencephalitis → ataxia, posterior paresis.
- Vasculitis affecting placenta or direct viremic spread to foal → abortion.
EHV-2
- Ubiquitous, therefore difficult to prove pathogenicity.
- Associated with pharyngeal lymphoid hyperplasia Pharynx: lymphoid hyperplasia , pharyngeal ulceration, and respiratory tract disease.
EHV-4
- Primary replication in respiratory epithelium → viremia → pyrexia and malaise → relocalization in respiratory tract → epithelial necrosis, congestion, and petechiation → nasal discharge and conjunctivitis.
- May localize in lymphocytes → necrosis of germinal centers of lymph nodes and reactive hyperplasia → local lymphadenopathy.
- May cause bronchitis or interstitial pneumonia in young animals.
- Secondary bacterial infection → mucopurulent nasal discharge, pneumonia.
EHV-5
- Recently described form of fibrotic interstitial lung disease, pathogenesis still unclear.
- Chronic respiratory disease and weight loss in older horses.
Timecourse
- Primary viral replication and viremia over initial 2-5 days.
- Course of acute disease may last several weeks.
- Latent infections may persist for life of animal.
Epidemiology
- Horses: 50% seropositive to EHV-1; almost 100% of adults seropositive to EHV-2.
- Subclinically or latently infected horses may act as reservoirs of infection.
- Virus transmitted by direct or indirect contact or erosol (EHV-3 transmitted venereally).
- Short-lived immunity (2-6 months), although mares which have aborted rarely abort again.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Dunowska M (2016)How common is equine herpesvirus type 1 infection?Vet Rec 178(3), 67-69 PubMed.
- Bazanow B Aet al(2014)Abortogenic viruses in horses.Equine Vet Educ26(1), 48-55 VetMedResource.
- Soare T, Leeming G, Morgan R, Papoula-Pereira R, Kipar A, Stewart J P & Hetzel U (2011)Equine multinodular pulmonary fibrosis in horses in the UK.Vet Rec169(12), 313 PubMed.
- Pusterla Net al(2011)Surveillance programme for important equine infectious respiratory pathogens in the USA.Vet Rec169(1), 12 PubMed.
- Kydd J H, Slater J, Osterrieder N, Antezak D F & Lunn D P (2010)Report of the second Havermeyer EHV-1 workshop, Steamboat Springs, Colorado, USA, September 2008.Equine Vet J42(6), 572-575 PubMed.
- Wong D M, Maxwell L K & Wilkins P (2010)Use of antiviral medications against equine herpes virus associated disorders.Equine Vet Educ22(5), 244-252 VetMedResource.
- Pusterla N & Mapes S (2008)Evaluation of an air tester for the sampling of aerosolised equine herpersvirus type 1.Vet Rec163(10), 306-308 PubMed.
- Luce Ret al(2007)Equine herpesvirus-1-specific interferon gamma (IFNy) synthesis by peripheral blood mononuclear cells in Throughbred horses.Equine Vet J39(3), 202-209 PubMed.
- Foote C E, Love D N, Gilkerson J R & Whalley J M (2004)Detection of EHV-1 and EHV-4 DNA in unweaned Thoroughbred foals from vaccinated mares on a large stud farm.Equine Vet J36(4), 341-345 PubMed.
- Wilson W D (1997)Equine herpesvirus 1 myeloencephalopathy.Vet Clin N Am Equine Pract13(1), 53 PubMed.
- Smith K C (1997)Herpes viral abortion in domestic animals.Vet J153(3), 253-268 PubMed.
- Donaldson M T & Sweeney C R (1997)Equine herpes virus myeloencephalopathy.Comp Cont Educ Pract Vet19(7), 864 VetMedResource.
- Whitwell K E & Blunden A S (1992)Pathologic findings in horses dying during an outbreak of the paralytic form of equid herpesvirus type 1 (EHV-1) infection.Equine Vet J24(1), 13-19 PubMed.
Other sources of information