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Ehv 1


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Dr. Jen led a discussion about EHV-1, explaining what the disease is and what to do about it.

Dr. Jen led a discussion about EHV-1, explaining what the disease is and what to do about it.

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  • 1. Update on Equine Herpes Virus-1
    Jenifer R Gold DVM ACVIM
    Mountain Horse Medical Center
    May 2011
  • 2. Update for Utah
    As of noon today
    4 quarantined facilities (Box Elder, Davis, Kane and Utah Counties)
    7 Confirmed cases on the quarantined facilities
    8 Suspect cases on the quarantined facilities
    2 cases euthanized due to recumbency/inability to rise
  • 3. Update for Outbreak in General
    Confirmed EHV-1 or equine herpes myeloencephalitis (EHM) have been reported in 9 states (AZ, CA, CO, ID, OR, TX, UT, WA)
    Arizona has 1 confirmed EHM and 1 euthanized.
    California has no new confirmed cases since 5/23/2011. So far they have 18 confirmed EHM cases. These cases came from Odgen UT (16) and Kern County Cutting Event (2), Bakersfield, CA. 1 case has been euthanized.
    Colorado has 9 confirmed cases of EHV-1. 2 of those horses were euthanized after showing severe neurological signs. 22 suspect cases. (not confirmed) 12 quarantine and hold orders in 8 counties (Bent, Boulder, Garfield, Gunnison, Larimer, Mesa, Morgan and Weld)
  • 4. Update for the Outbreak in General
    As of 5/26/2011 at 1 pm, Idaho has 5 horses on an EHV-affected facility already observing quarantine confirmed positive for EHV-1 in the past 24 hours. 2 of the horses attended the Ogden Cutting. 3 were stable mates at the same Idaho facility. Total of confirmed cases of EHV-1 in Idaho is 6. Three of the 6 have shown neurologic signs consistent with the neurological form of the disease. The other 3 have been febrile.
    New Mexico has 2 known positive cases, one has been euthanized , the other has been febrile with no other clinical signs.
    Oregon has 3 positive cases of EHV-1. None of the horses are showing clinical signs. 2 cases are in Clackamas and Umatilla County, the other is in Deschutes County.
  • 5. Update for the Outbreak in General
    Texas has 16 horses that were known to attend the cutting in Odgen UT. Only 1 horse so far has tested positive. The others are under quarantine.
    Washington State has 7 confirmed cases with no deaths. 3 of the cases are at WSU. Others are in Spokane, Thurston, Chelan and Asotin counties.
    Thus total number of horses with EHV-1 (fever, respiratory signs) or EHM (neurologic disease) =51 horses
    Total number of horses euthanized=8 horses
  • 6. What is Equine Herpes Virus?
    EHV-1 and EHV-4 are also known as Rhinopneumonitis
    EHV-1 causes respiratory disease, abortion and neurologic disease
    EHV-4 causes respiratory disease and infrequent abortions.
    Rarely (1 case) EHV-4 causes neurologic disease
  • 7. Respiratory Disease
    Clinical respiratory herpesvirus infections most commonly occur in young horses, usually weanlings and yearlings
    Widespread outbreaks can occur in stressful and overcrowded environments
    Older horses are important in the outbreak
    They become sub-clinically infected (no clinical signs) but shed virus!
  • 8. Respiratory Disease
    Clinical signs of respiratory disease
    Mild fever, coughing and nasal discharge
    Nasal discharge is typically clear
    Can progress to yellow thick purulent material
  • 9. Respiratory Disease
    Incubation period may be short as 2 days or as long as 10 days.
    Outcome is dictated by minimization of stress and lots of rest.
    Exercising horses frequently can develop prolonged hypersensitivity of the lower airways
    May cause a subtle decrease in performance
  • 10. EHV-1: Abortion
    There are usually no warning signs of abortion
    Can occur as early as 90 days
    Most cases occur between 7 and 9 months of gestation
    (Red bag abortion are common in horses infected with herpesvirus).
    In abortion storms over 50% of pregnant mares on the farm can have problems
    Red bag
    Aborted fetus
  • 11. Neurologic Disease
    Neurologic form of this disease can to be fatal and is the greatest cause for concern at boarding facilities, racetracks and horseshows.
    Most horses experience respiratory signs of disease for one to two weeks prior to the development of neurologic signs.
  • 12. Neurological Disease
    ~10% of horses get the neurologic form of herpes
    Stress (shipping or surgery) may trigger the onset of neurologic signs
    The virus will attack the spinal cord and brain stem.
  • 13. Neurological Disease
    The clinical signs commonly seen are:
    Hind-end weakness
    Urinary/fecal incontinence
  • 14. Latently infected carrier horse
    Pregnant mares
    Recruitment of
    New Hosts
    Into Cycle
    Infection of young horses
    Neurologic disease
  • 15. How is Herpesvirus Transmitted?
    Transmission occurs via respiratory route with infective droplets obtained from coughing and snorting horses.
    Shedding of the virus in nasal secretions can occur for 14 days.
    Contaminated hands and equipment (fomites) can spread the virus.
    Infection can be obtained from aborted fetuses, fluids and tissues.
    Mares that abort transmit infection via the respiratory route
  • 16. Transmission
    In perfect conditions the virus can last in the environment for 35 days.
    Typically however it last several weeks
    All horses have the potential to be carriers of the virus regardless of whether they have clinical signs
  • 17. Diagnosis
    Detection of virus from nasal swab or blood by viral isolation
    Polymerase chain reaction (PCR) tests can look for the virus in nasal secretions or whole blood buffy coat or placental and fetal tissue.
    Demonstration of a relative drop in lymphocytes and neutrophils (white blood cells) on a complete blood count (CBC)
    Demonstration of rising titers in serum collected two to four weeks apart
  • 18. Treatment
    Because EHV-1 is a virus, antibiotics do not work
    Supportive treatment: Guided by the severity and range of clinical signs.
    Vitamin E
  • 19. Treatment
    In most cases, horses that do not become recumbent have a good prognosis
    However, recovery may take weeks to months
    Horses that become recumbent and are unable to stand have a poor to guarded prognosis
  • 20. Vaccination
    Vaccinations for the respiratory form of EHV may not prevent the disease
    Will decrease the frequency, and severity of clinical signs
    Will decrease the shedding numbers of virus to other horses
  • 21. Vaccination
    The American Association of Equine Practitioners AAEP recommends the following vaccination schedule for EHV-1 and EHV-4 in the prevention of respiratory disease
    Foals/weanlings: First dose 4-6 months of age
    Second dose 5-7 months of age
    Third dose 6-8 months of age
    Later at 3 month intervals
  • 22. Vaccination
    Every 3-4 months
    Horses in training
    Every 3-4 months
  • 23. Vaccination
    All broodmares at the beginning of 3rd 5th, 7th and 9th month of pregnancy
    Currently there are 2 vaccinations labeled for the protection of abortion which are killed vaccines containing EHV-1
    Currently there is 1 vaccine that is a modified live virus vaccine
  • 24. Vaccination
    No vaccination currently available that is labeled to protect against the neurological form of equine herpes
    Preliminary work suggests the modified live virus vaccine may decrease clinical signs, but has not been totally confirmed
    The MLV has been shown to decrease viral shedding and potentially clinical signs…
  • 25. Controlling an Outbreak
    Isolate all new arrivals to the farm for 28 days
    If farms are quarantined, must remain in quarantine for 28 days.NO horse coming or going!
    Disinfect all areas of the barns and transport vehicles with either bleach (one part bleach to 10 pars water) or phenolic based disinfectants
    Take rectal temperatures daily and isolate any horse with a fever
  • 26. Controlling an Outbreak
    Disinfect all diagnostic tools such as endoscopes, after they are used on each horse
    Keep mares that abort in isolated areas away from the rest of broodmares
  • 27. Controlling an outbreak
    If horses are transported during an outbreak
    Call ahead and confirm requirements
    Some states require: Coggins, Health Certificate and proof of vaccination seven to 90 days prior to travel
    Both Wyoming and Colorado right now require a health certificate less than 72 hours old
  • 28. Questions????