Equine Herpesvirus
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Transcript of Equine Herpesvirus
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Equine
Herpesvirus (EHV)Myeloencephalopathy
A Guide To Understanding theNeurologic For o! EHV "n!ection
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#hat is EHM$
Equine herpesvirus myeloencephalopathy
(EHM) is another name for the neurologic disease
associated with equine herpesvirus (EHV) infec-
tions. Neurological signs appear as a result of
damage to lood vessels in the rain and spinal
cord associated with EHV infection. !nterferencewith the lood supply leads to tissue damage and
a susequent loss in normal function of areas in
the rain and spinal cord.
Neurological signs appearas a result of damage toblood vessels in the brainand spinal cord associatedwith EHV infection.
#hat are the equine herpesviruses$
"o date# nine EHVs have een identified world-
wide. "hree of these$EHV-%# EHV- and EHV-
'$pose the most serious health riss for domes-ticated horses and can have significant economic
impacts on the .*. equine industry.
+ EHV%&' ,an cause four manifestations of
disease in horses# including a neurologi-
cal form# respiratory disease# aortion# andneonatal death. EHM is most often due to
mutant or neuropathogenic strains of EHV-%#
so called ecause of a particular mutation in
the genome.
+ EHV%' ,auses a venereal disease calledequine coital eanthema that affects the
eternal genitalia.
+ EHV%' ,auses a nonfatal upper respiratory
tract disease in foals and is uncommonly
associated with aortion and rarely with
neurologic disease.
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Ho* coon are EHV%& in!ections$
y / years of age# almost all horses have een
infected with EHV-%. "he initial eposure gener-
ally occurs in foals from contact with their dams.
"he virus can then ecome latent# or inactive# in
the horse0s ody# setting up a carrier state that
is life-long. Horses of any age that are carriers ofEHV-% do not show any eternal signs of disease
when the virus is in a latent form. "he virus can
e reactivated during times of stress# such as
strenuous eercise# long-distance transport# or at
weaning.
"ransmission of EHV-%
1atently
!
n
1a
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!nfection of 2oal34dult Horse
!nfection of 5ther 2oals34dult Horses
"he transmission of EHV-% occurs after an eposure to anadult horse or foal with an active EHV-% viral infection. "hiseposure generally occurs via respiratory shedding of the
virus. "he infected adult horse or foal may or may not eehiiting clinical signs of disease.
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#hy should " +e concerned
a+out EHV%&$EHV-% is the primary cause of EHM. !n recent
years# there has een a mared increase in the
numer of EHV-% cases# especially EHM# reported
in the nited *tates. "here have also een several
outreas of EHM at large horse facilities andevents$at racetracs# horse show grounds#
veterinary clinics# and oarding stales. "he large
numer of horses that can e eposed on such
premises and the serious nature of the disease
have caused significant concern within the animal
health community and the .*. horse industry.
The virus can be reactivatedduring times of stress, such
as strenuous exercise, long-distance transport, or atweaning.
2urthermore# these recent occurrences of
EHM appear to meet the criteria of an emergingdisease. 4 disease is considered to e 6emerging7
when it satisfies at least one of three criteria8
%. "he disease is identified for the first time in a
region or country9
/. 4 disease changes in severity# type of animal
that can e infected# or other changes in
pathogen ehavior9 or
&. "here is a change in geographic range of a
disease or in its incidence within a range.
EHM liely meets the second criterion of an
emerging disease# as the recent EHV-% outreas
seem to e associated with a change in the sever-
ity and ehavior of the virus. !t is possile that the
reporting of EHV-% cases has increased# rather
than an actual increase in the numer and sever-ity of cases9 however# more data are needed to
mae such a distinction.
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Ho* is the virus spread$
"he most common way for EHV-% to spread
is y direct horse-to-horse contact. "his virus
is shed from infected horses via the respiratory
tract or through direct or indirect contact with
an infected aorted fetus and fetal memranes.
Horses may appear to e perfectly healthy yetspread the virus via the secretions from their
nostrils.
!t is important to reali:e that EHV-% can also
e spread indirectly through contact with physi-
cal o;ects contaminated with infectious virus.Eamples of such o;ects include8
+ "ac#
+
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#hen should " suspect y horse ight
have EHM$*igns of EHM include8
+ 2ever preceding neurologic signs
(either in a
horse diagnosed with EHM or in horses that
have een eposed to a horse diagnosed with
EHM)#
+ >ecreased coordination#
+ rine driling#
+ 1oss of tail tone#
+ Hind lim weaness#
+ 1eaningagainst a wall or fence
to maintain
alance#
+ 1ethargy# and
+ !naility to rise.
Horses may appear to be perfectly healthy yet spread
the virus via the secretions from their nostrils.
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Ho* is the disease diagnosed$
>iagnostics your veterinarian might perform
for
a live horse include8
+ Nasal swa collection for
laoratory eami-nation and detection of virus y polymerase
chain reaction (=,?) assay or y
virus isola-
tion9 and
+ lood collection to detect the
virus y =,?
assay or y virus isolation. lood samples
should e collected / to & wees apart for
levels of antiodies specific to EHV-%.
!deally# your veterinarian will collect oth nasalswa and lood samples to optimi:e arriving at a
diagnosis.
>iagnostics your veterinarian might perform
for
a deceased horse include8+ Necropsy eamination of a
horse with neu-
rologic disease that dies or has to e eutha-
ni:ed# or necropsy eamination of an aorted
fetus3fetal memranes. Necropsy provides animportant means of confirming the presence
of EHV-% disease.
"s there a treatent !or EHM$
"he standard form of care for EHM is primarilysupportive. "reatments may include intravenous
fluids or anti-inflammatory drugs. 4ntiiotics may
e used to treat a secondary acterial infection if
one develops9 however# antiiotics have no effect
on the equine herpesvirus itself. 4ntiviral drugs
have also een used to treat EHM
cases. ?esearch
on the efficacy of these drugs# their cost effective-
ness# and the optimal dosing regimen for EHM is
still underway.
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Ho* can " prevent EHV%&, the priary
cause o! EHM, !ro spreading to otherhorses$
"here are many steps you can tae to help
prevent the spread of EHV-%.
+ *top horse movement
if your animals may einfected with EHV-
%. "his is the most
important first step
horse owners can tae.
Horses should neitherenter nor leave a prem-
ises where EHM has
een diagnosed until
cleared y the veterin-
arian.
+ >o not allow horses
eposed to EHM
case(s) to have contact
with uneposed horses
on the premises.
+ !solate sic horses.
Horses that have
aorted or shown signs
of fever# respiratory
disease# or neurologic
disease should eseparated from healthy horses. !deally# the
sic horse(s) should e moved into a sepa-
rate uilding or paddoc on the premises# or
e transported to a veterinary hospital with an
isolation facility.
+ >o not share equipment among
horses on the
facility. *ince this virus can e spread from
horse to horse via contaminated o;ects such
as water3feed ucets or ridles# equipment
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-an " prevent EHM *ith vaccines$
Vaccines eist to control the respiratory and
aortion manifestations of EHV-%9 however# the
currently licensed vaccines are not laeled for
the prevention of EHM. niversity and private
researchers are looing into several eisting vac-
cines to determine if they protect against EHM. New vaccines for EHM are also eing studied.
ince this virus can be spread from horse to horse via con-taminated ob!ects such aswater"feed buc#ets or bridles,e$uipment should not be
shared among horses.
Use!ul .esources
2or more information related to EHV# EHM# and
iosecurity# please refer to the following docu-
ments and epartment of
4griculture
(*>4)
*>484=H!*8V*8,E4H. /@@A. Equine Her-
pesvirus Myeloencephalopathy8 Mitigation
Eperiences# 1essons 1earned#and 2uture
Needs. NBC//.@D@A. http833www.aphis.usda.
gov3vs3nahss3equine3
+ *>484=H!*8V*8,E4H8,E!. Emerging
4nimal >isease Notice. /@@D. Equine Herpes
Virus Myeloencephalopathy8 4
=otentially
Emerging >isease.
http833www.aphis.usda.gov3vs3ceah3cei3taf3emerging diseasenotice.files3ehv.pdf
+ *>484=H!*. iosecurity$the ey to
eep-
ing Four Horses Healthy.
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+ niversity of ,alifornia ,enter
for EquineHealth (,EH)
http833www.vetmed.ucdavis.edu3ceh3topics.htm
+ 4merican 4ssociation of Equine
=ractitioners
(44E=)http833www.aaep.org3controlGguidelinesGnon-
memer.htm
http833www.aaep.org3vaccinationGguidelines.
htm
+ !owa *tate niversity iological?is Manage-
ment (?M)
http833www.cfsph.iastate.edu3?M3equinere-
sources.htm
http833www.cfsph.iastate.edu3?M3disinfects.
htm
For More "n!oration
"o find out more aout EHM# please contact8
*>44=H!*-V*-,E4H N??, uilding# M.*. /ED
/%C@ ,entre 4venue
2ort ,ollins# ,5 A@C/I-A%%D
(JD@) 'J'-D@@@
E-mail8 N4HM*Kaphis.usda.gov
http833nahms.aphis.usda.gov
The U.S. Department of Agriculture (USDA) prohibits discrimi-
nation in all its programs and activities on the basis of race, color,
national origin, age, disability, and where applicable, sex, marital
status, familial status, parental status, religion, sexual orientation,
genetic information, political beliefs, reprisals, or because all or part
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disabilities who require alternative means for communication of pro-
gram information (Braille, large print, audiotape, etc.) should contact
USDA’s TARGET Center at (202) 720–2600 (voice and TDD).
To file a complaint of discrimination, write USDA, Director, Office
of Civil Rights, 1400 Independence Avenue, S.W., Washington,
D.C. 20250–9410 or call (202) 800 795 3272(voice) or (202) 720-
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6382(TDD). USDA is an equal opportunity provider and employer.
Mention of companies or commercial products does not imply
recommendation or endorsement by the USDA over others not men-
tioned. USDA neither guarantees nor warrants the standard of any
product mentioned. Product names are mentioned solely to report
factually on available data and to provide specific information.
Issued December 2008
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United States Department of Agriculture
Animal and Plant Health Inspection Service
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