Equine herpesvirus type III (EHV-3)
Qualitative detection of equine herpesvirus type III by polymerase chain reaction
herpesvirus type III (EHV-3) causes coital exanthema, a
contagious genital infection (vulva in mares, penis and scrotum
in stallions), spread venereally and characterized by numerous
small blisters or spots, sometimes called ‘the pox’. The
blisters burst and become secondarily infected by skin bacteria,
then heal leaving white (de-pigmented) skin spots. The disease
has no direct effect on the fertility of stallions or mares, but
natural mating must be stopped to allow the disease to run its
course (usually 10 days to 2 weeks to complete healing) and to
prevent further spread of infection.
coital exanthema is probably transmitted only in the acute phase
of the disease; horses do not appear to shed the virus after
lesions have healed. However, the existence of a carrier state
is unclear; some believe that the scars that persist after
healing can identify potential carriers, while others state that
asymptomatic carriers have not been identified. Immunity is
short-lived, but evidence from stallions shows that recurrence
is not likely within a single breeding season.
has one antigenic type but also has small and large plaque
variants in tissue culture, indicating that variation may occur
in the severity of field outbreaks. Although the primary route
of transmission is venereal, outbreaks have been documented in
which transmission occurred via contaminated supplies and
instruments or by the use of a single glove for rectal
examination of many mares. It is probably for this reason that
EHV-3 has also been isolated from animals that have not been
diagnosis can be based on clinical signs but must be confirmed
by identifying (using electron microscopy) the virus in cells
from the margin of ulcers. However, this electron microscopy
technique to identify this virus is not very sensitive. Acute
and convalescent samples for serum neutralization or complement
fixation tests have been proposed as diagnostic tools for EHV-3
infection, but these tests must be interpreted carefully because
EHV-1 and EHV-4 have also been isolated from genital lesions.
Molecular detection of EHV-3 by PCR is the most sensitive,
specific and accurate tool in assessing the infectivity of an
affected horse (Dynon et al., 2001; Kleiboeker and Chapman,
Help confirm the disease causing agent
Shorten the time required to confirm a clinical
diagnosis of EHV-3 infection
Help ensure that horse populations are free of EHV-3
Early prevention of spread of this virus
Minimize personnel exposure to this virus
Safety monitoring of biological products that derive
Dynon, K., Varrasso, A., Ficorilli, N., Holloway, S., Reubel,
G., Li, F., Hartley, C., Studdert, M. and Drummer, H (2001)
Identification of equine herpesvirus 3 (equine coital exanthema
virus), equine gammaherpesviruses 2 and 5, equine adenoviruses 1
and 2, equine arteritis virus and equine rhinitis A virus by
polymerase chain reaction. Aust. Vet. J. 79:695-702.
Kleiboeker, S.B. and Chapman, R.K. (2004) Detection of equine
herpesvirus 3 in equine skin lesions by polymerase chain
reaction. J. Vet. Diagn. Invest. 16:74-79.
Specimen requirements: 0.2 ml whole blood in EDTA (purple top) tube, or lesion swab, or 0.2 ml fresh, frozen or fixed tissue.
Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.
specimen types, if there will be a delay in shipping, or during
very warm weather, refrigerate specimens until shipped and ship
with a cold pack unless more stringent shipping requirements are
specified. Frozen specimens should be shipped so as to remain
frozen in transit. See shipping
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