May 2007

Leesburg Reopened
The Marion duPont Scott Equine Medical Center resumed full operations, including inpatient and emergency care, on Monday, April 2. Th e quarantine imposed by the Virginia State Veterinarian’s Offi ce on Feb. 20, was in response to the suspected infection of two horses with equine herpesvirus type-1 (EHV-1). Eighteen patients were held at the hospital during the restriction. Th ree of those hospitalized horses tested positive for EHV-1 – two of which have since tested negative for the disease and remain in the center’s Animal Biosafety Level 2 isolation unit and one of which was euthanized due to unrelated medical conditions. No horses died at the center from EHV-1.

According to Dr. Nat White, Jean Ellen Shehan Professor and Director of the Marion duPont Scott Equine Medical Center, the state veterinarian authorized the release from quarantine based on stringent criteria established by the hospital’s leadership including the isolation of groups of horses, the length of time for which the horses have shown no symptoms and a rigorous testing protocol.

“The center’s facilities have been thoroughly cleaned and disinfected to ensure the safety and well-being of our patients, and we are ready to once again provide the highest quality of care and service to the equine community,” said White.

Dr. Martin Furr, Adelaide C. Riggs Chair in Equine Medicine, noted that the university teaching hospital environment proved integral in containing this infection. “Because our faculty members conduct cutting-edge research into equine disease, we were prepared to handle this type of an outbreak,” said Furr. “Although additional research into the prevention and treatment of EHV-1 is needed, our experience has taught us that the immediate implementation of emergency management procedures is the best way to stop the spread of this type of contagion.”

According to Furr, new criterion have been added to the center’s biosecurity guidelines as a result of the infection including the mandatory use of hand disinfectants and restrictions on visitor access to hospital facilities.

“We know from conversations with our peers and other industry experts that our biosafety procedures are among the strictest,” said Furr. “Biosecurity guidelines are essentially living documents that are always being reevaluated and we decided to augment our existing protocols with these additional measures in order to further protect our patients.”

“We would like to thank the regulatory officials, university representatives, industry members and horse owners who worked closely with the center’s leadership throughout the quarantine,” said White. “We look forward to continued cooperation among these parties in pursuing the well-being of the horse and of the equine industry.”

Clients with questions concerning the reopening can visit equiery. com and click on the links for the Marion duPont Scott Equine Medical Center.

The Marion duPont Scott Equine Medical Center is a Leesburg, Va., based full-service equine hospital that is owned by Virginia Tech and operated as one of three campuses that comprise the Virginia- Maryland Regional College of Veterinary Medicine.

Herpes Query: Incubation Periods and Why Did Maryland & Virginia Responses Differ So? 
The mid-Atlantic herpes crises ended in March, but our readers questions still linger.

Q: Isn’t the incubation period for for EHV-1 (equine herpes) up to 17 days? If so, why did Maryland take hold orders off and release horses before the incubation period was over, whereas Virginia did not?
A: Maryland State Vet, Guy Hohenhaus, DVM, responds:
One must be careful when comparing the processes used by different states to manage similar, but not identical situations. States are sovereign entities, which have the right to manage most internal aff airs as they see their interests. Given that laws, regulations and authority vary between 2 states, and diff erent individuals make up the response management teams, it is no surprise that there would be some diff erences in approach. The real question you raise is to the reasonableness of the Maryland response to EHV-1.

The 17 day incubation time you cite is an extreme outside range, most being within a week or less and incubation to clinical disease. We are using test methodologies which detect current infection, not current disease or evidence of past disease. Th e time frames on this are thus much shorter. Only a fraction of infections lead to clinical disease, so using that yardstick could lead to missed or “silent” infections.

If an animal was exposed , there would be PCR evidence of that infection within a few days, but certainly within 7 days. We focused the testing and observation on the higher risk animals, those which had Leesburg exposure, rather than secondary contacts. If those animals had no evidence of the virus after 7 days away from Leesburg, there is a very high probability they were only exposed, but NOT infected. No infection=no EHV-1 disease; no EHV-1 disease =no transmission to others.

Thus, with a negative PCR 7+ days post Leesburg, we were very confi dent that a discharged EMC patient had not brought the virus home and the property could be released.

Additionally, if there was any evidence of fever, unexplained respiratory disease or neurologic disease on the property from the time the patient returned, that protocol cannot be employed, hence, 2 farms remained restricted longer.

Lastly, the best measure of success or failure is the absence or presence of new cases traced back to the original outbreak (outcomes). I would certainly expect that had our approach been overly “lenient,” that we would have seen some evidence of sick EHV-1 horses by well before the 17 day post discharge time frame. We do not. We continue to receive reports from veterinarians, but to date, none has yielded a case of EHV-1. Th e outcomes experience in VA has been quite similar, with only very limited disease spread beyond the EMC, as evidenced by very low rates of infection in discharged patients.

Our goal is the same as Virginia’s – to control this outbreak as quickly and eff ectively as possible, while minimizing the necessary negative impacts on the industry. We take our duty to protect the industry very seriously and that duty includes doing everything necessary, lawful and proper to respond. We also subscribe the Hippocratic notion of “First do no harm,” in that we have determined that for purposes of protecting Maryland horses, anything additional would be unnecessary, a burden on the industry and ultimately harmful.

Remember, our authority is limited to that which tends to control livestock diseases. That said, individuals, businesses and other entities are free to make their own choices about restricting activities. Please consult with our staff in advance to determine the best way to accomplish the goal, which is motivating the decision to restrict activities.