Lindström, A, 2006. Distribution and transmission of American foulbrood in honey bees.
Doctor's dissertation.
ISSN 1652-6880, ISBN 91-576-7071-4
The distribution of Paenibacillus larvae spores, the causative agent of American foulbrood
was studied on three different levels in the honey bee system; the apiary level, the colony
level and the individual honey bee level. The increased understanding of spore distribution
has been used to give recommendations regarding sampling of adult honey bees. The
vertical transmission of P. larvae spores through natural swarms has been described for the
first time and artificial swarming as a method for control of American foulbrood have been
evaluated.
The results demonstrated that there is no practical difference in spore load between supers
and brood chambers, and that the spore load in samples of adult honey bees on the different
levels correspond to the clinical disease status of the colony. The study on individual bees
showed that spores are unequally distributed among the bees and that as more bees get
contaminated each positive bee also contains more spores. This may present a problem
when sampling from colonies with low levels of clinical disease, although the study on
colony and apiary level showed no false negatives. A model for calculating the number of
bees that needs to be sampled to detect P. larvae in a composite sample of adult bees, given
certain detection levels and proportions of positive honey bees in the sample, was developed
The swarm study demonstrated vertical transmission of P. larvae spores. Furthermore, the
artificial swarm study showed that single and double shaking are equally effective treatment
methods, and that the original disease status is of little importance for the spore load
decrease