A few links I found to help (and seem reliable).
Michigan Department of Natural Resources:
http://www.michigan.gov/dnr/0,4570,7-153-10370_12150_12220-26481--,00.html
Kansas State University Agricultural Experiment Station and Cooperative Extension Service...
Deerman, is it possible to treat new birds for blackhead just in case and be able to run them with peafowl? I've heard with Metronidozale?
If you were able to treat for it with any new birds joining the flock, would this solve the issue of running them together (such as peafowl with guineas...