WOOSTER — As Ohio hunters prowl the woods this week to make the most of deer-hunting season, animal-disease authorities are targeting an illness hidden in the brains of deer.

Chronic wasting disease, a fatal neurological condition that affects deer and elk, has not been found in Ohio. However, its recent appearance in the Midwest has prompted state authorities to test and monitor Ohio’s deer.

The Ohio Department of Agriculture’s Animal Disease Diagnostics Laboratory will analyze brain tissue from 500 white-tailed deer killed by Ohio hunters in 26 counties — most of them in the southeastern Ohio, where the largest number of deer are hunted.

“It’s probably a matter of time before we find chronic wasting disease in Ohio,” said Srinand Sreevatsan, a scientist with the Ohio Agricultural Research and Development Center in Wooster. “However, it’s unlikely that the disease will be found this hunting season because the animals being killed are very young, and CWD takes at least 18 months to develop.”

CWD-infected deer and elk have excessive salivation, trouble swallowing, difficulty judging distance, lack of coordination and drooping ears. The disease is fatal. It is not known exactly how the disease is transmitted.

“Transmission seems to be more horizontal than vertical,” Sreevatsan explained. “That means the disease is spread by direct or indirect contact between animals: through saliva, urine, blood and other bodily fluids. There isn’t much evidence to believe that the disease is passed on during birth.”

Unlike mad cow disease, CWD has not been found to infect humans. However, the World Health Organization recommends people should not eat any part of a deer or elk showing symptoms of the disease.

CWD was first detected in 1967 in northeast Colorado. As of December 2002, it has been diagnosed in deer and elk in 11 states and the Canadian provinces of Alberta and Saskatchewan. Wildlife experts suspect deer and elk farming may be responsible for spreading CWD.

For more than 30 years, CWD was restricted to areas west of the Mississippi River. But this year, it turned up in Wisconsin’s wild deer herd, prompting officials there to begin an effort to kill 25,000 animals in the southwestern part of that state. Last month, the threat moved even closer to Ohio, when a deer with CWD was killed in northern Illinois.

Ohio has a wild herd of 575,000 white-tailed deer. Another 6,000-plus animals live in captivity on the state’s 515 deer farms, most of which are in Holmes, Wayne, Stark, Tuscarawas and Geauga counties.