Hard drought conditions coupled with water source, gnats/midges that carry the disease.

Many folks call it blue tongue which is prevelant in sheep. However it is not with whitetail. EHD is what is killing deer andhas many of the same symptoms as blue tongue. Cattle are innoculated for EHD. Some old farmers call it the circling disease also.

I've found both does and bucks dead because of the disease. Any deer healthy, sick, young or old can be effected.

It really sucks as some of the deer you'll watch on a fairly regular basis prior to EHD may not be around for the season.

All you can do is hope for the best.