Do some of my bees have CBPV? Today I watched 5 bees at the entrance to Hive D. They were on the ground below the landing board. They weren't moving much. Two or three of them were considerably darker than I'd expect.
Could it be the weather? Perhaps these bees were just chilled. Am I a Bee Hypochondriac? Certainly I have no idea whether this hive has this disease.
I took a moment to read the CBPV factsheet from Beebase. The virus is often present in the European honey bee at low levels. Stress causes the expression of the virus, usually in 'the peak of spring and summer'. I don't think that today is the peak of anything. There is a litter of decaying bee corpses outside Hive D. The hive was notable for its' prolific production of brood at the expense of stores. I hefted the hive and it feels ok for stores. What, if anything, could be causing this stress? Could they be too cramped?
There are more questions than answers. I shall revisit the bees and try to take pictures. I'll take an extra super and put that on. If they're too cramped then extra space could ease the problem.