Re: EFB options
SP, I have not had EFB or AFB in more years than I can count, but dealt with both in the past. EFB is easily cleared with oxytetracycline. Fortunately, most bees will eliminate EFB on their own if given time. I treated EFB with Oxy about 30 years ago and requeened the colonies. There were no recurrences.
The $65000 question is where did it come from. EFB can be brought in with infected equipment. It is far more likely that a nearby beekeeper had a colony collapse with disease that your bees robbed out.
NW Alabama, 50 years, 20 colonies and growing, sideliner, treatment free since 2005, 14 frame square Dadant broodnest