At my last inspection, I noticed that the brood pattern on several frames had become spotty. The colony is from a package started the second week of April, with a queen who previously had a good, though not wall-to-wall, laying pattern.
Looking closer, I saw that there were diseased brood in several cells, but not all looked alike.
Some brood, perhaps 15 cells on a frame, showed symptoms that match European Foulbrood. Uncapped larvae had turned into off-white "goop" on the lower wall of the cell. From a distance it looked as though the cell had been partly filled with carpenter's glue.
Larvae could be pulled out with tweezers more or less whole, but were wet and melty and easily torn with pressure. They smelled slightly sour, like yogurt.
A couple of brood, maybe two or three looked like prepupae, laying along the bottom wall of the cell, but with gray/dark mottled heads, like the larvae near the center of the photo above. I've also seen images that show larvae like this as evidence of sacbrood. I have not seen any completely "sac"ed larvae.
There was also evidently healthy young brood on the same frame, including immediately adjacent to melted larvae. I did not see much healthy older brood. I did not locate the queen. There were some eggs, but laid in patches rather than solidly filling in. 40% or more of the frame appeared to me to be empty.
Has anyone encountered symptoms like this? Can I provide further information? What can I do to help the colony recover? :'(