Transcript RHINOPNEUMONIT IN EQUIDE

Legislative background of horse
infectious disease surveillance
principles in EU with particular
reference to Equine Rhinopneumonitis
Prof. Dr. IVAYLO CHENCHEV, PhD, DVSc
NATIONAL DIAGNOSTIC AND
RESEARCH VETERINARY MEDICAL
INSTITUTE - SOFIA
EHV - DEFINITION
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EHV is not a new disease
It was first identified in 1936 in USA from Dimock and
Edward
Equine Rhinopneumonitis is an acute viral disease in
equines, which is manifested with abortion in the end of
pregnancy and heavy lung disorders in neonates and old
horses.
The disease characterizes with very variable symptoms –
from appearing of vesicles on no hears parts of body,
respiratory symptomatic, abortion on last trimester of
pregnancy, paresis and paralysis, birth to weak foals that
show signs of respiratory distress, lethargy, and poor
nursing ability. These foals usually die within the first week
of life.
Equine Herpes Virus 1 is obligated for the nervous
symptoms
EHV - SPREADING
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Except horses in natural conditions the disease
is appeared in donkeys, mules and ponies.
All wild equines are got ill but it is more
sensibility of clinical manifestation of the
disease.
Sex, breed and age do not influence on
receptivity against infection.
It is known that the thoroughbreds horses are
more receptivity as the semi thoroughbreds and
domestic breeds horses.
Thoroughbreds horses manifested the acute
symptoms and these animals left for a long time
viral holders and shedders.
EHV - SPREADING
“Equine Herpes Virus” refers to
the
disease
–
Equine
Rhinopneumonitis
 “Equine
Rhinopneumonitis”
refers to the virus – Equine
Herpes Virus serotype 1 and 4
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CLASSIFICATION, ETHIOLOGY AND
EPIZOOTOLOGY
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The EHV is of the family
SUBFAMILY ALPHAHERPESVIRINAE
Herpesviridae, which is included
Varicellovirus
the three subfamilies
Equine herpesvirus 1
Alphaherpesvirinae,
Betaherpesvirinae, and
Equine herpesvirus 4
Gammaherpesvirinae.
Equine HV 6 = asinine HV 1
Viruses of the subfamily
Simplexvirus
Alphaherpesvirinae have short
replication cycle (<24h), and had
Equine coital exantema HV 3
different hosts.
Equine HV 8 = asinine HV 3
Subfamily Betaherpesvirinae are
SUBFAMILY BETAHERPESVIRINAE
included genus's Cytomegalovirus,
Muromegalovirus and Roseolovirus
Cytomegalovirus
which are not important for
Equine herpes virus 2
veterinary medicine.
Subfamily Gammaherpesvirinae are SUBFAMILY GAMMAHERPESVIRINAE
classicized genus’s
Rhadinovirus
Lymphocryptovirus (viruses on sea
and river fish) and Rhadinovirus
Equine HV 5
(diseases in monkeys and
Equine HV 7 = asinine 2
primates).
CLASSIFICATION, ETHIOLOGY AND
EPIZOOTOLOGY
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Alfaherpesvirinae are large-sized 150 170 nm,
enveloped , positive-sense,
stranded DNA, with an icosahedral
nucleocapsid with 162 capsomere.
CLASSIFICATION, ETHIOLOGY AND
EPIZOOTOLOGY
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Equine Herpes Virus-1 is sensitive on
high temperature and it is fast
inactivate in between 37º - 50ºC.
In 4ºC It stored infectious qualities 7 8 days.
In lyophylisated condition it can save
more 2 years.
CLASSIFICATION, ETHIOLOGY AND
EPIZOOTOLOGY
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Only serotypes 1 and 4 provocated serious
diseases in equines.
Equine Coital Exanthema causes by Equine herpes
Virus serotype 3. This disease is not serious and
horses are cured very fast from it.
The serotypes 2 and 5 don’t manifests the clinical
symptoms and its are estimated only in
laboratory conditions.
Its gave raise to other diseases in equines like
West Nile Fever, Salmonellosis, Pasterellosis, and
other bacterial diseases.
ЕHV-1 и EHV-4 are mostly respiratory pathogens
and Its caused damages is respiratory tract and
respiratory distress.
CLASSIFICATION, ETHIOLOGY AND
EPIZOOTOLOGY
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Inter - generational
(vertical) transmission of
the viruses from latently
infected dam to foal;
Post infection
establishment of viral
latency in affected foals;
Periodic reactivation and
shedding of latent
herpesvirus to result in
homo-generational
(horizontal) horse-to-horse
virus transmission
EHV - PATHOGENESIS
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The latent carrier state is critically important to the
maintenance and spread of EHV-1 and EHV-4.
Periodic reactivation of latent EHV-1 and EHV-4 is
associated with episodes of stress or corticosteroid
administration.
The stimuli for herpesvirus reactivation are diverse
and include surgery, boarding, parturition, prolonged
transport, weaning, lactation, inclement weather, and
social disruption.
Reactivation of the latent herpesviruses may occur in
the absence of concurrent clinical signs.
Respiratory tract shedding from carrier horses in
which latent virus has been reactivated has been
documented, and shedding of reactivated virus into
the respiratory mucus is often not accompanied by
clinical signs.
EHV - PATHOGENESIS
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The incubation period for signs of respiratory
infection
after natural exposure to
the
herpesviruses ranges from 2 to 5 days.
Horses infected for the first time may shed the
viruses for prolonged periods (up to 14 days).
Peak virus shedding occurs during the first few
days after the onset of nasal discharge and
coincides with the febrile phase of the infection.
Respiratory signs of EHV-1 or EHV-4 infection
(nasal discharge and fever) are initiated by the
direct viral cytopathic destruction of airway
epithelium.
Mild pulmonary lesions develop in some foals.
EHV - SYMPTOMS
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Clinical symptoms of the respiratory form of the
disease are characterized with fever, lethargy,
absence of appetite, rhinitis, pharingithis, laryngithis,
water eyes, bronchitis and pneumonia which are get
pass for 2 - 5 days.
The viral shedding in this time is the highest.
The cough which is appeared in stud farm contributed
for penetration of the virus.
The clear secretions are laden with high numbers
(titres) of infectious virus. As infection progresses, the
nasal discharge becomes thicker and white in colour.
These latter secretions often dry as crusts around the
nostrils. Nasal discharge can become mucopurulent
(thick, opaque and yellowish) with secondary
bacterial infections e.g.
Streptococcus equi ss
zooepidemicus
CLINICAL SYMPTOMS
CLINICAL FORMS
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Abortion and other pathology
conditions of the pregnancy – neonatal
birth, death, and birth to weak foals;
Respiratory syndroms – pneumonia and
bronchitis;
Influence like form;
Herpes meningoencephalitis;
Latent and Innaparent form;
Endometritis and Metritis;
ABORTION
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Abortion storms can follow the introduction of an
infected mare into a group of susceptible pregnant
mares.
However, most EHV1 induced abortions only involve one
or two mares in a group. Infection gains entry via the
respiratory tract.
Abortion usually occurs during the last three months of
pregnancy.
Mares carrying EHV1 infected foetuses usually have no
outward clinical signs of disease and thus abortion is the
only evidence of EHV infection.
The aborted foetus and placenta carry high levels of
virus and are therefore very infective to other horses on
the property.
Very occasionally, abortions can be caused by EHV4.
PERINATAL MORTALITY
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Mares infected in late pregnancy may give
birth to weak foals that show signs of
respiratory distress, lethargy, and poor
nursing ability.
These foals usually die within the first week
of life.
Large amounts of virus are shed in the
respiratory secretions of EHV1 infected foals,
thus they may be a major source of infection
for other mares on the property.
OTHER DISEASES
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Foals with respiratory disease caused by EHV1 may
also suffer from eye disease, which usually manifests
itself as uveitis and/or chorioretinitis. In very severe
cases, the retina is destroyed and blindness occurs.
Severe lung disease in young horses following EHV1
respiratory infections has been reported. It is termed
"pulmonary vasculotropic EHV1 infection" and clinical
signs include: a high fever, decreased feed intake,
severe depression, and respiratory distress.
Onset of clinical signs is sudden and sometimes horses
may be found dead.
Affected horses are found to have inflamed and
damaged blood vessels throughout their body
systems, especially within the lungs.
MYELOENCEPHALOPATHY
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The central nervous system (CNS) can become
affected following EHV infection.
Onset of neurological signs usually occurs within
6 -10 days of the initial EHV1 infection.
Neurological signs appear suddenly and are at
their worst within 2-3 days of onset, generally
they
are
non-progressive.
Locomotor
disturbances that vary from dragging a hind limb
to complete quadriplegia can occur.
Horses with mild signs have a relatively good
chance of recovery.
Horses that are recumbent (cannot stand) for
longer than 2 days have a poor rate of survival.
EHV - DIAGNOSIS
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Laboratory diagnostic success with EHV-1 and EHV-4 is
influenced by the techniques used for collection, handling,
transport, storage and processing of the clinical specimens.
Success is greatest when the nasal mucus specimens for
laboratory testing are taken within 48 hours of the onset of
illness when the horse is still pyrexic and the nasal
discharge still serous in nature.
Respiratory secretions are collected with a cotton swab
inserted through the ventral nasal meatus and advanced
into the nasopharynx. At least 20 ml of venous blood should
be collected for attempted virus isolation and transported
chilled, but not frozen, to the laboratory.
The period for greatest success in virus isolation from the
blood is 4 - 10 days after onset of respiratory disease.
EHV - DIAGNOSIS
Virus isolation
ELISA for antibodies and antigens
 Virus Neutralization Test
 Real Time PCR
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DIAGNOSIS
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The cytopathic effect of EHV-1 and EHV-4 is
characteristic, and seroidentification of the two
herpesviruses can be made with type-specific
monoclonal antibodies.
Amplification of viral DNA using PCR is a rapid,
sensitive and increasing utilized assay for
detection of EHV-1 or EHV-4 respiratory tract
infection.
When direct antigen detection methods are used
for a rapid laboratory diagnosis of EHV-1 or EHV4, it is important to confirm the direct test results
by virus isolation.
EHV - DIAGNOSIS
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Electro microspopic
picture of EHV 1
after virus isolation
EHV - DIAGNOSIS
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Immunofluorescent
detection of viral
antigens
EHV - DIAGNOSIS
ELISA for
distinguishes the
antibodies against
two serotypes EHV 1
and EHV 4
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EHV - DIAGNOSIS
Conventional PCR
for EHV 1 and EHV 4
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TREATMENT
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There is no specific treatment for equine herpes virus
infections.
Minimising stress, good nursing care and cessation of
training are essential for a swift recovery.
Up to four weeks rest may be necessary. If the horse
returns to work too quickly, a recrudescence of virus
or a secondary bacterial infection may result, thus
predisposing the horse to the development of
pneumonia.
Horses unwilling to eat/drink may require fluid and
electrolyte replacement and those with secondary
bacterial infections require antibacterial therapy.
Horses with severe CNS disease require intensive
nursing care e.g. daily cleansing, topical care of bedsores and turning.
VACCINES AGAINST EQUINE RHINOPNEUMONITIS
Vaccine
Company
(country)
Vaccine
type
Virus
Components
Manufacturer’s
Recommendatio
ns for
DUVAXYN EHV-1,4
Fort Dodge
(Belgium)
Inactivated
EHV-1 & EHV-4
Abortion &
respiratory disease
EQUIFFA
Merial (Europe)
Inactivated
EHV-1; EIV-1 &
EIV-2
respiratory disease
EQUIGUARD
Boehringer
Ingelheim (USA)
Inactivated
EHV-1 & EHV-4
respiratory disease
EQUIVAC EHV-1/4
Fort Dodge (USA)
Inactivated
EHV-1 & EHV-4
respiratory disease
FLUVAC EHV-4/1
PLUS
Fort Dodge (USA)
Inactivated
EHV-4 & EHV-1;
EIV-1 & EIV-2
respiratory disease
PNEUMABORT K +
1B
Fort Dodge (USA)
Inactivated
EHV-1 (1P & 1B
strains)
Abortion &
respiratory disease
PRESTIGE
Intervet (USA)
Inactivated
EHV-1 & EHV-4
respiratory disease
PRESTIGE II
Intervet (USA)
Inactivated
EHV-1 & EHV-4;
EIV-1 & EIV-2
respiratory disease
PRESTIGE V
Intervet (USA)
Inactivated
EHV-1 & EHV-4;
EIV-1 & EIV-2; EEE
& WEE; Tet
respiratory disease
EQUIGARD-FLU
Boehringer
Ingelheim (USA)
Inactivated
EHV-1 & EHV-4;
EIV-1 & EIV-2
respiratory disease
DOUBLE-E FT EHV
Fort Dodge (USA)
Inactivated
EHV-1 & EHV-4;
EIV-1 & EIV-2; EEE
& WEE; Tet
respiratory disease
PRODIGY
Intervet (USA)
Inactivated
EHV-1
Abortion
RESEQUIN
Intervet (Europe)
Inactivated
EHV-1 & EHV-4
respiratory disease
RESEQUIN PLUS
Intervet (Europe)
Inactivated
EHV-1 & EHV-4;
EIV-1 & EIV-2
respiratory disease
PREVENTION
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Infected horses can shed large amounts of virus
in nasal secretions and can provide a significant
reservoir of infection for other horses.
It is important to isolate infected horses. Horses
arriving on the property should ideally be isolated
for 3-4 weeks however.
Breeding and training horses should be kept
segregated to reduce the chance of pregnant
mares becoming infected.
Reducing stress in the horse’s environment will
help to decrease stress induced shedding of virus
from latently infected carrier horses e.g. feed
well, drench and avoid mixing different social
groups.
PREVENTION
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Vaccination against EHV1 and EHV4 respiratory
disease is recommended as part of a preventative
herd-health programme for all horses at risk of
becoming infected.
An ideal vaccination protocol for at risk horses would
be: two vaccinations spaced at 4-6 weeks apart just
prior to weaning (5 months of age) with a booster
every 6 months while the horse is exposed to periods
of increased risk e.g. training, racing, competitions.
Foals that are exposed to field infections or who have
had insufficient colostrum can be vaccinated earlier
than 5 months of age.
Mares at stud (barren and pregnant) can be
vaccinated as a management aid to prevent EHV
induced abortions
PRENEVTION
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Vaccination does not prevent respiratory infection
however;
it provides active immunisation and therefore
decreases the severity of the clinical signs of
respiratory disease caused by EHV1 and EHV4.
Also, abortion may still occur in vaccinated mares but
the risk of an abortion storm is greatly reduced.
It is important to realise that some vaccinations
protect horses against the respiratory form of the
disease and against abortion while others only protect
against respiratory disease.
Vet is decided what kind of protocol and which
vaccine is the best suits for the different categories of
horses.