A treating vet in Virginia still isn’t sure what made three of his clients’ horses sick this spring while generating widespread concern on an Internet message board as “Whisper Syndrome” (for background information, see www.TheHorse.com/ViewArticle.aspx?id=5588). Antibody titer results searching for a definitive diagnosis or rule-out on the bacterial disease listeriosis came back inconclusive in May. But Thach Winslow, DVM, of Blacksburg, Va., says listeriosis cannot be ruled out in the cases.

Winslow explained, “The results are circumstantial…they were certainly not conclusive that Listeria is involved, but there was certainly enough evidence there to keep it on the suspicious list.

“There probably will never be a true diagnosis on those horses,” he added. “Similar cases in the future should probably be considered Listeria as a differential to rule out, hopefully by brain culture.”

It was suggested on the message board that the horses might have become sick from eating round hay bales. Winslow stresses that the bales were only suspect and his recommendations for feeding them haven’t changed–select high quality bales, store them inside, and offer them free choice to horses. For more information, see www.TheHorse.com/ViewArticle.aspx?id=5815