01/30/2017 3:20PM

Nasal-swab tests come back mostly negative for EHV-1


Four of five nasal-swab samples taken from horses currently isolated at Fair Grounds because of the equine herpesvirus returned negative results from a lab in Kentucky after testing positive for the wild strain of EHV-1 at a Louisiana lab.

The five positives for EHV-1 were called by a lab at Louisiana State University that has been used for tests throughout the EHV-1 event at Fair Grounds that led to a general quarantine of the backstretch by the state’s Department of Agriculture. Another portion of samples taken at the same time from the five horses was sent to a lab at the University of Kentucky, which confirmed one positive but returned four negative results.

Horsemen and veterinarians have questioned the efficacy of nasal-swab testing for the wild strain of EHV-1 since mass testing of asymptomatic horses began in early January at Fair Grounds. When all the horses in barn 14 were nasal-swabbed, 19 positive tests were called.

“I think a lot of people started questioning it then,” said trainer Michelle Lovell, who is based in barn 14 and trains one of the horses whose sample tested negative at the Kentucky lab after a positive was called in Louisiana. “It shocked everybody.”

Samples from the five horses have been sent to a laboratory at Iowa State University for another round of testing.

Two horses in barn 14, one of whom had to be euthanized, contracted the more serious neuropathogenic strain of EHV-1 in late December. That outbreak quickly was contained, but horses throughout the backstretch began testing positive for wild-type EHV-1 after horsemen began reporting any horse with a fever to regulatory officials.

The Department of Agriculture briefly instituted a protocol of testing every horse – even healthy animals – in barns that had recorded an EHV-1 wild-type positive, which led to nearly 40 horses being isolated on the Fair Grounds property. The full-barn testing protocol was withdrawn after a few days following protestations from veterinarians and horsemen that nasal-swab tests were unsuited for use on healthy horses.

However, horses already placed in isolation must twice test negative for EHV-1 before they can rejoin the general population, and it was from this group that the divergence in lab results was discovered over the weekend.

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