| Equine herpes virus |
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| State vet advises precautions with equine herpes virus-1 (rhino) |
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There have been 2 cases of Equine Herpes Virus-1 (EHV-1), a highly contagious respiratory virus that may cause mild neurological signs, reported in Oregon since mid-July. During this same time, five horses in Washington also exhibited clinical signs that were consistent with EHV-1. All these horses attended the same weekend show in Oregon on July 11th. These horses are not infected with the severe neurological or mutant strain of EHV-1 that was diagnosed in horses on the east coast and California this past year.
At this time, the office of the state veterinarian does not have any restrictions on horse movement in Oregon.
Even though EHV-1 is not a regulatory disease, and is not required to be reported, I am asking veterinarians and horse owners to call our office with confirmed cases (503-986-4680).
I am urging horse owners to take precautions. Veterinarians should work closely with their equine clients to develop plans that address the clients' ability to prevent EHV-1 in their horses. If a horse is suspected of having EHV-1, it should be isolated and equipment should not be shared.
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| EVH-1 informational links |
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The following are links for EHV-1 from the California Department of Food and Agriculture and UC Davis that will help readers become informed about this disease.
The full text of the California Department of Food and Agriculture may be accessed at:http://www.cdfa.ca.gov/ahfss/ah/equine_herpes_virus.htm
The full text of UC Davis Center for Equine Health disease information and links may be accessed at:http://www.vetmed.ucdavis.edu/ceh/topics.htm
Some of the points made on these Web sites are summarized below.
- At this time enforcement of strict biosecurity measures and hygiene practices are likely to be effective reducing the risk of acquiring infection.
- Stress and lack of previous exposure to the virus may make the horse more susceptible to becoming clinically ill.
- Regarding vaccination, UC Davis reports that recent research demonstrates that viral shedding is much reduced in horses with high circulating titers of virus-neutralizing (VN) antibody, as well as in horses that have been vaccinated recently with the Rhinomune MLV vaccine.
- Many times when horses are incubating the virus, fever in excess of 102 F may be the only observable sign of infection.
- Rapid separation and isolation of identified suspect cases and biosecurity are key elements for disease control. Horse-to-horse contact, contaminated hands, equipment, tack, feed, and aerosol transmission all play a role in its spread.
- As with all contagious diseases, if horses are commingled with strange horses, an unknown degree of inherent risk exists for exposure to EHV-1. Many factors may enhance or reduce the amount of risk. If the choice is made to commingle with a population that has the potential to harbor EHV-1 infected individuals, there is no foolproof way to completely eliminate the risk of exposure.
- Since EHV-1 is considered to be endemic within the horse population, random testing of normal horses for EHV-1 by PCR diagnostics can and likely will detect horses with nonreplicating (dead) viral DNA; latent, low-level, transient carriage of virus; or viral levels that are not sufficient to pose a significant risk for disease transmission.
- At this time the significance of a positive PCR in an asymptomatic horse is unknown, regardless of the test being employed or the laboratory performing the test. There is simply not sufficient information yet acquired to justify or recommend control measures or quarantine procedures for horses testing positive for EHV-1 in the absence of clinical signs of disease.
- If horses are exposed to new horses, especially in stressful competitive environments or following long distance travel, it is helpful to establish a disease-monitoring plan. Temperature monitoring (2 times per day) is a tool to be used for a differential diagnosis that could include EHV-1.
- The good news is that to date the overwhelming majority of horses recently known to have had exposure to incubating EHV-1 horses have not developed clinical disease.
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