My thought on the topic goes like this... EHD is a viral disease with at least 7 known strains. Viral diseases currently don't have any sort of cure for one strain, let alone 7. Immunity from the current strain of EHD most deer contract in the midwest will take upwards of 100 years to happen, which sucks because none of us will be around to see that! So, with no cure to actually help once the EHD virus has entered a deer ... The only thing plausible I see at this point is preventing the midge from actually biting the deer - whether that be through an ingredient in the feed that gives a deers coat some kind of insect repellent type odor or feature that repelled insects/midges, or through the roller system that Sligh1 discussed. I would think surely there has got to be some sort of formula safe for deer to intake that would prevent insects from biting them... I don't know. I'm not well versed in that department.