Five American bisons at Vienna’s Schönbrunn Zoo have died due to a suspected infection from a sheep herpes virus, as confirmed by the zoo on Wednesday in a Facebook post. Following careful consideration, the zoo also decided to euthanize the sole remaining bison calf to prevent further suffering and transmission. The zoo now no longer has any bisons. “We deeply regret the loss of these magnificent animals,” stated the zoo in its announcement.

Preliminary pathology results point to an illness likely caused by a sheep virus. The zoo explained that Ouessant sheep from the petting area might be potential carriers of the virus, although it poses no risk to humans. Keeping the lone bison calf alone was deemed inhumane and legally impractical, and transferring it to another location wasn’t an option due to the potential risk of infection.

Zoo experts are now focused on preventing further outbreaks. In the coming days, the Ouessant sheep from the petting zoo will be transferred to other facilities to mitigate infection risks. The zoo highlighted that any sheep herd can carry the sheep herpes virus, which remains harmless to the sheep but can be deadly to bisons and other cattle species. “By relocating the sheep, we aim to reduce the risk of additional infections,” the zoo emphasized.