The feed stores in my area won't have a clue about blackhead, and I'd bet the same is true for the extension offices. Sure, call the feed store, extension offices, but then call an avian pathologist in your State and ask them if what they think.
Think about this... how many of you send *all* dead chicks, chickens, poults, turkeys, etc off for necropsy or do them yourselves? Then think about your neighbors, what do they do with theirs? How can agency possibly know what diseases are in what parts of your town, county or State?
-Kathy
The small feed store in my area did know what it was and was able to tell me that there had been no reports of it around, same with the extension office. Yes, for sure do your due diligence but I have been hatching and raising my birds together for over a year with absolutely no issues with blackhead...
Also, when one of my Turkey Hens contracted Cocci last year I did call an avian vet and asked about Blackhead (I didn't know what was wrong with her) and was told the same thing I had been told from the feed store and extension office.