I am not sure what EHD is? I have heard of CWD and Blue Tongue. I have heard north central missouri has had issues with CWD and that blue tongue has been found in all parts of Missouri and really bad in Illinois. If I had deer missing for a period of time I would check all the water sources in the area as this is typically where the deer with blue tongue are being found. If these searches turn up empty, the other answer is this time of year deer start to disappear from areas and show up in others due to pre rut activity and searching for does and new food sources.