Five horses in Reddington, Ind., are dead after contracting botulism, according to an alert from the International Society for Infectious Diseases (ISID). The alert indicates the botulism toxin was ingested via an "unknown food source," likely the hay the horses consumed.

The ISID alert also noted that five additional horses residing at the same facility consumed the same hay as the deceased animals; those horses are currently being treated for botulism. The report indicates the sick horses received a botulism antitoxin and had not consumed as much potentially contaminated hay as the five animals that died. As of March 19, the report said, all were still alive.

It was not reported if any of the affected horses were vaccinated against botulism.

Botulism is a fatal neurologic disease of horses caused by toxins produced by the anaerobic, spore-forming, soil-dwelling bacterium Clostridium botulinum