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American foulbrood in a honeybee colony: spore-symptom relationship and feedbacks between disease and colony development

Stephan, Jörg and Rodrigues De Miranda, Joachim and Forsgren, Eva (2020). American foulbrood in a honeybee colony: spore-symptom relationship and feedbacks between disease and colony development. BMC Ecology. 20 , 1-14
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Abstract

Background: The most severe bacterial disease of honeybees is American foulbrood (AFB. The epidemiology of AFB is driven by the extreme spore resilience, the difficulty of bees to remove these spores, and the considerable incidence of undetected spore-producing colonies. The honeybee collective defence mechanisms and their feedback on colony development, which involves a division of labour at multiple levels of colony organization, are difficult to model. To better predict disease outbreaks we need to understand the feedback between colony development and disease progression within the colony. We therefore developed Bayesian models with data from forty AFB-diseased colonies monitored over an entire foraging season to (i) investigate the relationship between spore production and symptoms, (ii) disentangle the feedback loops between AFB epidemiology and natural colony development, and (iii) discuss whether larger insect societies promote or limit within-colony disease transmission.
Results: Rather than identifying a fixed spore count threshold for clinical symptoms, we estimated the probabili-ties around the relationship between spore counts and symptoms, taking into account modulators such as brood amount/number of bees and time post infection. We identified a decrease over time in the bees-to-brood ratio related to disease development, which should ultimately induce colony collapse. Lastly, two contrasting theories pre-dict that larger colonies could promote either higher (classical epidemiological SIR-model) or lower (increasing spatial nest segregation and more effective pathogen removal) disease prevalence.
Conclusions: AFB followed the predictions of the SIR-model, partly because disease prevalence and brood removal are decoupled, with worker bees acting more as disease vectors, infecting new brood, than as agents of social immu-nity, by removing infected brood. We therefore established a direct link between disease prevalence and social group size for a eusocial insect. We furthermore provide a probabilistic description of the relationship between AFB spore counts and symptoms, and how disease development and colony strength over a season modulate this relationship. These results help to better understand disease development within honeybee colonies, provide important estimates for further epidemiological modelling, and gained important insights into the optimal sampling strategy for practical beekeeping and honeybee research.

Authors/Creators:Stephan, Jörg and Rodrigues De Miranda, Joachim and Forsgren, Eva
Title:American foulbrood in a honeybee colony: spore-symptom relationship and feedbacks between disease and colony development
Year of publishing :2020
Volume:20
Page range:1-14
Number of Pages:14
Publisher:BMC
ISSN:1472-6785
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Ecology
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Agricultural Science
Keywords:Apis mellifera, Paenibacillus larvae, Group size, Enzootic disease, Host–pathogen dynamics, Social immunity, MCMC, Detection, SIR-model, Diagnosis, Host density
URN:NBN:urn:nbn:se:slu:epsilon-p-104877
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-104877
Additional ID:
Type of IDID
DOI10.1186/s12898-020-00283-w
ID Code:16777
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Swedish Species Information Centre
(NL, NJ) > Dept. of Ecology
(S) > Dept. of Ecology
Deposited By: SLUpub Connector
Deposited On:31 Mar 2020 11:34
Metadata Last Modified:31 Mar 2020 11:34

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