University of Kentucky animal disease experts have determined that ducks found dead at a lake in Nicholasville were killed by botulism.

The university's Livestock Disease Diagnostic Center in Lexington says the botulism is the type that occurs naturally when air temperatures rise and water and oxygen levels drop in ponds.

Nicholasville-Jessamine County Parks and Recreation Department Director Duane McCuddy told the Lexington Herald-Leader that eight birds died at Lake Mingo Park over the weekend. The university center examined three of the ducks, and McCuddy says blood drawn from one sick bird has been sent to a Wisconsin lab.

The botulin bacteria causes paralysis by attacking the nervous systems of birds and poses no threat to humans.