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Equine Herpesvirus-1(ehv-1)

On Dec.  23, 2015 the Pennsylvania Department of Agriculture (PDA) received laboratory confirmation that three horses euthanized over a two-day period due to acute, severe neurological impairment were infected with the neuropathogenic variant of EHV-1. 

These horses were at a private, pleasure-horse boarding facility in the Doylestown area of Bucks County (Mile View Farm.)  This facility has been and remains under a formal quarantine by PDA.

Animals on the premises are being monitored carefully for signs compatible with active EHV-1 infection.  Barn owners, management, staff and horse owners have been very proactive and are compliant with quarantine and biosecurity requirements. 

Private practitioners involved with this facility are also very involved and have been providing guidance to affected horse owners as well as their many other concerned clients.

PDA is responding to this situation, as it has for the past several years, based on a science-based protocol involving minimum quarantine of 21 days from the last significant clinical finding (e.g. fever) as well as the use of polymerase chain reaction (PCR) testing for EHV-1 when appropriate.  

Private veterinarians can help PDA by correcting any misinformation related to this issue, helping clients to avoid assigning blame for this situation that is simply a disease that can happen anywhere there are horses, and, as always, reminding their equestrian clients of some of the biosecurity practices they can utilize to mitigate risk.  The American Association of Equine Practitioners (AAEP) website has resource information available at

Veterinarians are also reminded to review their own biosecurity precautions so that, should they be called upon to see a patient that may have this highly contagious disease or a patient with an unrelated condition on an affected premises, they do not carry EHV-1 to other patients at that site or, even worse, to patients at other locations.  It is very important that the veterinary community set a good example for horse owners by maintaining sound sanitation and infection control practices.

The same advice applies to other professionals such as farriers, equine dentists, chiropractors, trainers, equine massage therapists and others who travel to equine facilities.

As a reminder, neuropathogenic EHV-1 is reportable to PDA on suspicion.  That means a veterinarian must report a suspected case to PDA right away even if they do not have confirmatory test results. PDA can then post a quarantine for the premises to ensure that no equine animals leave while test results are confirmed and all parties involved can immediately begin to focus efforts on reducing disease transmission.  The veterinarians involved with these initial cases reported this situation promptly, enabling PDA to respond much sooner than if we had waited for confirmatory laboratory results.

Also, although the veterinarians involved with these cases knew the appropriate samples to take, there is often confusion about what samples should be submitted for EHV diagnosis from a live animal.  Veterinarians, please make note of the supplies you would need to take the proper samples and obtain them now.  The time to find the right-sized blood tubes or the right swabs is NOT when you are looking at a neurologically-impaired horse.  Please refer to the submission guidelines for the laboratory where you will be sending the samples for their specific preferences, but whole blood in purple top (EDTA) tubes and polyester tip/plastic shaft nasal swabs in empty red top tubes are usually preferred for RRT-PCR testing for EHV-1.

Thank you for everyone’s continued vigilance in identifying cases of reportable diseases and assistance with the dissemination of clear, calm, factual information to the equestrian community.  Please go to the following link for up-to-date information regarding this outbreak: