KAILUA-KONA >> A mysterious disease affecting wild horses in Waipio Valley on the Big Island has prompted an investigation by Hawaii agencies and veterinarians.

The disease makes the animals unable to walk, resulting in a number of wild horse deaths, West Hawaii Today reported Monday.

The condition appears to be neurological, said veterinarian Tim Richards, a Hawaii County councilman. Symptoms first show through an abnormal gait as the horse’s muscles begin to atrophy, usually starting with the hind limbs.

Veterinarian Kelleyerin Clabaugh said she first heard about the outbreak nearly a month ago. No symptoms have appeared in the area’s domestic horse population, she said.

Clabaugh started the investigation, conducting blood tests on two of the horses. She ruled out a viral brain inflammation and a number of other contagious diseases.

The cause could be correlated with something the horses are eating, she said.

“It most likely looks like a disease caused by mold spore toxins,” Clabaugh said. “That is not a diagnosis, but it is a high suspicion.”

A necropsy on a recently deceased horse was conducted last week by Richards and a team from the Hawaii Department of Agriculture. The team is led by Jason Moniz, veterinary program manager for the department’s Animal Disease Control Branch.

“These horses that have been affected have been in one area and nothing has spread to any of the domestic horses down there, so we’re kind of leaning toward something these animals are consuming,” Moniz said. “There are multiple species of plants down there that have toxic principles.”

Samples from the horse were sent to labs for testing. Moniz expects results in about three weeks.