Equine Viral Diseases INAG 120 – Equine Health Management September 19, 2011.
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Transcript of Equine Viral Diseases INAG 120 – Equine Health Management September 19, 2011.
Equine Viral Diseases
INAG 120 – Equine Health Management
September 19, 2011
What’s a Virus?VIRUS
Structure Outer layer
(envelope) is spiky Protein coat DNA/RNA
Electron micrograph of a rotavirus. The one on the right has antibodies attached which prevent it from infecting cells© GrahamColm
What’s the difference between a virus and a bacterium?
VIRUS BACTERIUM
More About Viruses
VIRUS VERY small REPRODUCTION
Depend on host cells for reproduction Attach to a cell and inject genes or are
absorbed Host cell mass-produces virus
Equine Viruses
Equine Herpes Virus (EHV) Equine Encephalomyelites Equine Influenza Equine Infectious Anemia West Nile Virus Equine Viral Arteritis Rabies
Equine Herpes Virus
Species Specific Three Subfamilies: alpha, beta, gamma
9 documented strains, but only 5 affect domestic horses
EHV-1 () Subtype 1
Rhinopneumonitis (respiratory form) Abortion Birth of weak foals Peracute vasculitis Neurological
EHV-1…
EHV-1 is common throughout the world Can be sudden and deadly High temperature “Fulminating” respiratory disease May see all 5 of the syndromes at once Horses of all ages are affected Mares 3-9 months pregnant most
susceptible Abortion storm virus first identified in the 1940s
EHV-1…
Viral incubation for 2-10 days: Fever (102 - 107º F for 1-7 days) Malaise, depression, anorexia Congestion and serous discharge from the
nostrils Swollen lymph nodes Mild incoordination to severe ataxia, paresis
and paralysis Loss of bladder tone, tail tone, skin
sensation in hind limbs
EHV-1
Treatment and prognosis: Supportive nursing If horse remains standing, prognosis is good NSAID’s to control malaise and fever
Encourages eating Fluid therapy if dehydrated Antibiotics to prevent secondary bacterial
infection (especially if respiratory disease) Corticosteroids to reduce nerve inflammation
Equine Herpes Virus
EHV-2 and EHV-5 Gamma Family “Ubiquitous” but rarely causes disease Found in nearly 100% of healthy foals Can cause problems in the following
diseases: Conjunctivitis in young foals May act as a forerunner infection that leads to
Rhodococcal (through immune suppression)
Equine Herpes Virus
EHV-3 Venereal Disease Equine Coital Exanthema
Rare but important ($$)
Doesn’t causedeath
Self-limiting Characteristic
lesions on genitalia of stallions and mares
Equine Herpes Virus
EHV-4 Respiratory infection only (“Rhino”) Non-fatal Severe, widespread outbreaks in young
horses Foals 3 years old in training Not a problem in older horses (develop
immunity)
EHV-1 Outbreaks: USA & UK # outbreaks caused by
Five-year interval
# Outbreaks Wild-type Mutant
1970-1975 1 0 1
1976-1980 3 0 3
1981-1985 4 2 2
1986-1990 6 1 5
1991-1995 5 1 4
1996-2000 6 2 4
2001-2005 32 2 30
EHV in Ohio
University of Findlay, January 12, 2003: 138 horses quarantined at the English riding facility
35-40 horses showed obvious neurological signs
12 horses died Within 5-6 days of first horse showing symptoms,
80-90% of horses had fevers
Strain confirmed as EHV-1 Respiratory and neurological symptoms
Not sure where the strain came from
All horses were current on vaccinations!
EHV in Maryland
Montgomery County, March 2004: 12 horses exhibit signs of neurologic illness 5 horses died Farm houses mostly polo ponies
Strain confirmed as EHV-type 1 Confirmed after multiple tests on July 8 Not sure where the strain came from Hindlimb ataxia, inability to stand, coma
All horses were current on vaccinations!
EHV in Maryland Howard County, Columbia Horse Center
March/April 2005 – June 2005 Facility strictly quarantined 4? horses euthanized
Pimlico, Eastern Shore, January 2 – March 2006 EHV-1 detected in one barn 4 Barns quarantined (but not quickly enough)
EHV-1 spreads to training farm on the Shore, leading to the euthansia of 2 horses.
Pimlico closes on January 23rd (reopens February 8th) Pennsylvania and Kentucky Tracks not accepting horses from
Maryland or allowing horses to race in Maryland EHV shows up at Laurel Park, January 25th
EHV-1 at Marion DuPont Scott Equine Medical Center February 2007 – March 29, 2007
Equine Encephalomyelitis
Arthropod-borne viruses that cause Central Nervous System dysfunction and moderate to high mortality Western (20-30% fatal) Eastern (70-90% fatal) Venezuelan (50-
75% fatal) Transmitted by mosquitoes!
Not horse-horse or horse-human
Zoonotic Diseases!
Equine Encephalomyelitis Clinical Signs:
Generally occur 5 days after infection Death may occur within 2-3 days Ataxia, wandering, impaired
vision, reduced reflexes, circling, inability to swallow, drooling, fever
Paralysis usually followed by death
EEE
VEE – “Paddling”
Equine Encephalomyelitis
Diagnosis: Laboratory tests on blood samples or necropsy
tissues
Treatment: Successful for mildly affected animals Supportive nursing care
Control: Vaccination one month prior to mosquito season
Equine Influenza
Symptoms: Harsh, dry cough Loss of appetite Depression Watery nasal discharge
Can lead to pneumonia!
Normal trachea Image courtesy of Dr. Issel and Gluck Center
Trachea after cilia destroyed by flu
Image courtesy of Dr. Issel and Gluck Center
Equine Influenza
Treatment Fresh air, rest Avoid dust Antibiotics to control secondary infection
Prevention: Vaccination! Most vaccines are effective against multiple
strains
Equine Infectious Anemia
“Swamp Fever” Horses are the only known natural host! No treatment available to eliminate EIA from an
infected horse Horses surviving EIA can
relapse and/or pass it on to other horses Lifetime Quarantine Euthanasia
2006: Appeared in Ireland
EIA
Clinical Signs Sudden onset of high
fever of 104º - 108º Severe depression Depressed appetite Weight Loss Weak/incoordination Jaundice Ventral edema Rapid destruction of red blood cells
EIA – Ventral Edema
EIA – Symptoms
EIA
Subacute form is most common Similar symptoms to acute, but not as
severe Death not as common
Chronic EIA: Horses are unthrifty and lack stamina May have acute or subacute attacks
EIA – Method of transmission
Blood from infected horses
Blood-sucking flies, mosquitoes
Needles Surgical
instruments Dental floats Bridle Bits
EIA - Diagnosis
COGGINS TEST Dr. Leroy Coggins of Cornell University Only 10 cc of blood is needed for the test Results can be available in 48 hours Most states require a negative Coggins test for
transported horses Most shows require negative Coggins test for
participants Some states require negative Coggins for sales
West Nile Virus
Vector-borne virus first in this hemisphere in 1999
Humans, horses, and birds are incidental hosts
Many horses infected with WNV do not become ill
Approximately 33% dieZoonotic Diseases!
WNV
Control: Mosquito Control! Eliminate standing water Mosquitoes can breed in as little as an inch
of water Vaccination –95% control rate WNV Antibody for horses already infected
(from Novartis Animal Vaccines, Inc.)
September 24, 2004
November 1, 2005
September 19, 2006
November 27, 2007
September 16, 2008
Equine Viral Artereitis
Acute upper respiratory infection caused by a herpes virus
Similar to influenza and rhino Fever (102-106º) Nasal discharge All age groups susceptible Can cause abortion (approximately
50%) Edema of the limbs Increased respiratory rate Skin rash
EVA
Most common in Saddlebreds and Standardbreds
Most animals recover without treatment Vet may prescribe antibiotics to prevent
secondary infection Transmission:
Inhalation of droplets from infected horses STD!!!
Rabies
Neruotropic Rhabdovirus Saliva of infected animal horse Travels up the NERVES to the brain Reproduces in the brain Sheds virus through the salivary glands BLOOD TEST WON’T DIAGNOSE
DISEASE!!! Saliva test?
Zoonotic Diseases!
Rabies
Symptoms: Neurological disorder, choking, weakness,
staggering, unprovoked excitement Behavioral changes are most common May take 2-6 weeks or even 3 months to show
symptoms after infection
NO EFFECTIVE TREATMENT!! Prevention = annual vaccination Problem in horses in the Mid-Atlantic
Raccoon strain is predominant here