Halfway through the quarantine period following a case of the neurologic form of equine herpesvirus-1 (EHV-1) in the National Stud in Newmarket, England, no new cases have been discovered.

“We are still observing the guidelines set out in the code of practice, and the infection remains isolated to just that one filly,” said National Stud spokeswoman Amy Taylor.

A young maiden mare was imported from France on Jan. 20 for live cover at the stud, but began to show signs of illness after a week in the stud’s health isolation unit (where all imported horses are kept for two weeks following arrival). She had difficulty getting up from lying down and had problems urinating, the facility’s staff reported. Veterinarians sent samples for testing, and the stud immediately stopped all animal transport in and out of the stud on Jan. 28. Two days later, when laboratory testing showed positive results for EHV-1, public visits to the stud were suspended, as well. As the virus can spread via clothing and other materials, the stud is allowing only necessary workers, who are following strict biosecurity procedures including protective clothing and shoe disinfectants, to access the facility.

As the Thoroughbred breeding season opens, the infection is all the greater risk to the industry as it spreads quickly and can cause abortion, stud officials said