The following excerpts bring home the fact that AFB spores can be present at high levels in colonies that do not show symptoms. In the effort to remove diseased material the bees actually spread the spores all over the hive equipment.
A common method to detect AFB is by visual inspection for clinical
symptoms manifested as punctured sealed brood, dead larvae
or larval remains (Shimanuki, 1997). In larger beekeeping
operations, visual inspections of all brood combs are cumbersome.
Light infections, with only a few diseased cells visible, may
easily remain undetected. Some honey bees express hygienic
behaviour and are able to clean out diseased and dead larvae
(Spivak & Reuter, 2001), and colonies can contain many P. l. larvae
spores on bees or in honey without showing clinical symptoms.
Lindström, A., & Fries, I. (2005). Sampling of adult bees for detection of American foulbrood (Paenibacillus larvae subsp. larvae) spores in honey bee (Apis mellifera) colonies. Journal of apicultural research, 44(2), 82-86.
We found little evidence of any beneficial effects of the
hygienic behaviour of brood removal on containing the
epidemic, especially since adult bees simultaneously also
act as vectors of the disease. We extend the discussion further
to larger eusocial societies exhibiting stronger social
immunity by showing this seems not to apply for American
foulbrood in honeybees as workers are removing diseased
brood but also vectoring the disease.
Stephan, J. G., de Miranda, J. R., & Forsgren, E. (2020). American foulbrood in a honeybee colony: spore-symptom relationship and feedbacks between disease and colony development. BMC ecology, 20(1), 1-14.
PLB
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