Equis ISSN 2398-2977

Reproduction: coital exanthema - EHV 3

Synonym(s): Genital horse pox, eruptive venereal disease, equine venereal vulvitis/balanitis, coital vesicular exanthema

Contributor(s): Sarah Binns, Terry Blanchard, Rachael Conwell, Graham Munroe, Sarah Stoneham

Introduction

  • Coital exanthema is a highly contagious disease of the external genitalia primarily regarded as venereally transmitted.
  • Cause: equine herpesvirus-3 (EHV-3).
  • Signs: vesicles, pustules and ulcers on external genitalia; systemic signs occur rarely in stallions.
  • Diagnosis: lesions, virus detection, serology.
  • Treatment: self-limiting; prevent secondary bacterial infection.
  • Prognosis: good.
Print off the Owner factsheet on Equine herpesvirus - EHV to give to your clients.

Pathogenesis

Etiology

Predisposing factors

General
  • Mare or stallion involved in breeding.
  • Venereal contact at coitus.

Specific

  • Other transmitters include insects, veterinary surgeons/grooms, instruments, ultrasound probe.
  • Damage to the vulva from foaling injuries or surgery may encourage infection.

Pathophysiology

  • Equine herpesvirus-3 infection   →   venereal transmission   →   lesions on external genitalia.
  • Viral replication in stratified epithelium of epidermal tissue within skin or at mucocutaneous margins.
  • Highly contagious.
  • Non-venereally transmitted form recognized in maiden fillies and colts.
  • Hypothesized that latent infection is established in sciatic and/or sacral ganglion.
Stallions
  • Venereal infection with EHV-3   →   stallions may rarely show systemic signs, eg dullness, anorexia, pyrexia.
  • Lesions (papules or nodules) up to 2 mm diameter develop first on penis, then prepuce 2-5 days later   →   vesicles up to 1.5 cm diameter   →   circumscribed pustules with raised border   →   slough and ulcerate (3-10 mm in diameter)   →   heal over 10-14 days by granulation leaving depigmented spots. Penis and prepuce may be painful and edematous.
  • Some affected stallions refuse to breed.
  • Recurrent cases can occur; recrudescence can also be seen after foaling.
  • Secondary bacterial infection delays healing and increases inflammation/pain.

Mares

  • Rarely show systemic signs.
  • Vulvar mucosal and perineal skin lesions   →   multiple discrete circular nodules (2 mm diameter) progressing to vesicles/pustules which rupture to scabrous erosions   →   hyperemic erosions with sharply defined margins   →   heal over 10-14 days unless complicated by secondary bacterial infection.
  • Secondary bacterial infection withStreptococcus zooepidemicus  Streptococcus spp  is common.
  • Signs include vulval discharge, tail switching, increased frequency of urination and arching of back.
  • Lesions around the anus can be associated with anorectal lymphadenopathy, constipation and tenesmus.
  • Delayed foaling or reduced pregnancy rates may occur due to missed breeding opportunities.
  • Rarely may cause reduced conception rates for that particular mating.
  • Some mares show recurrence of lesions, usually around the time of parturition.

Maiden fillies and colts

  • Non-venereal spread from infectious in-contacts.
  • Pyrexia and painful coalescing skin lesions over the anus and vulva in fillies, and perineum, scrotum and inside hindlimbs in colts.

Immunity

  • Reinfection without clinical signs is common.
  • Virus may remain latent in genitalia.
  • Use of corticosteroids has caused recrudescence experimentally.

Timecourse

  • Incubation period 5-10 days.
  • Unless complicated the lesions granulate and heal within 2-3 weeks leaving depigmented circular lesions.
  • Covering can begin during the next estrus.

Epidemiology

  • EHV-3 usually passed from subclinically infected mare   →   stallion at breeding   →   transmitted to susceptible mares prior to developing clinical signs.

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.
  • Barrandeguy M & Thiry E (2012)Equine coital examthema and its potential economic implications for the equine industry.Vet J191(1), 35-40 PubMed.
  • Barrandeguy Met al(2010)Outbreak or rhinitis caused by equine herpesvirus type 3.Vet Rec166(6), 178 PubMed.
  • Barrandeguy Met al(2008)Experimental reactivation of equine herpesvirus-3 following corticosteroid treatment.Equine Vet J40(6), 593-595 PubMed.
  • Blanchard T L, Kenney R M & Timoney P J (1992)Venereal disease.Vet Clin North Am Equine Pract8(1) 191-193 PubMed.
  • Uppal P Ket al(1989)Equine coital exanthema (EHV-3 virus) infection in India.Zentrabl Veterinarmed [B]36, (10) 786-788 PubMed.
  • Pascoe R R (1981)The effect of equine coital exanthema on the fertility of mares covered by stallions exhibiting the clinical disease.Aust Vet J57(3) 111-114PubMed.
  • Feilen C P, Walker S T, Studdert M J (1979)Equine herpesvirus type 3 (Equine coital exanthema) in New South Wales.Aust Vet J55, (19) 443-444 PubMed.
  • Pascoe R R &Bagust T J (1975)Coital exanthema in stallions.J Reprod Fertil SupplOct, (23) 147-150 PubMed.
  • Bitsch V (1972)Cases of equine coital exanthema in Denmark.Acta Vet Scand13, (2) 281-283 PubMed.
  • Gibbs E P, Roberts M C, Morris J M (1972)Equine coital exanthema in the United Kingdom.Equine Vet J4, (2) 74-80 PubMed.

Other sources of information


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