[Spur9]

If a colony is exposed, what is the shortest possible time before recognizable symptoms occur?

Online test with correct answer stated of 12.5 days. Assuming 12.5 days is accurate, anyone care to explain the logic behind this?

 

[AR Beekeeper]

AFB kills the larva in the prepupa stage or when the larva first becomes a pupa. The prepupa stage is days 9-11 from the egg laid, the pupa is on day 12. The cell is caped before the larva becomes the prepupa, so the bees must find the dead prepupa/pupa and begin to chew off the capping before the beekeeper can see the dead brood. This usually happens on day 12.

 

[Spur9]

Thx for the reply. I was thinking that the infected larvae would show signs prior to capping and so the time would be shorter than 12 days.

 

[AR Beekeeper]

If my memory is correct, AFB, Sacbrood, and Chalkbrood all die after the cell is sealed and the larva straightens out in the cell. The beekeeper doesn't see anything wrong with the dead larva until the bees detect the dead larva and uncap it. It's the same situation with dead pupa, the bees have detected varroa reproducing in the cell, or the pupa has died from some virus and the bees uncap and remove it.

 

[squarepeg]

the 12.5 days answer seems to suggest that older larvae fed with afb and then capped say within a few days afterward don't succumb to the disease?

 

[AR Beekeeper]

I would think that 12.5 days was the average of the ages in the study, or studies, that the test makers used in their program.

It is very hard to infect larvae older than 48 hours with AFB, in most trials the larvae never develop the disease after that age. I have read about studies in which 1/3rd of the colonies fed spores would never develop the disease. EFB is considered to be more infectious than AFB.

 

[Spur9]

the 12.5 days answer seems to suggest that older larvae fed with afb and then capped say within a few days afterward don't succumb to the disease?

Everything thing that I have read about AFB points to larva between 12 hours to 36 hours susceptible to the bacteria. I guess larvae 2+ days from egg hatching are safe.