Validation of diagnostic methods for European Foulbrood on commercial honey bee colonies in the United States

Authors: MILBRATH, MEGHAN - Michigan State University; FOWLER, PETER - Michigan State University; Abban, Samuel; Lopez, Dawn; Evans, Jay

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2021
Publication Date: 11/1/2021
Citation: Milbrath, M., Fowler, P., Abban, S.K., Boncristiani, D.L., Evans, J.D. 2021. Validation of diagnostic methods for European Foulbrood on commercial honey bee colonies in the United States. Journal of Insect Science. 21(6):6. https://doi.org/10.1093/jisesa/ieab075.
DOI: https://doi.org/10.1093/jisesa/ieab075

Interpretive Summary: European foulbrood is an increasingly important disease in honey bee colonies. Outbreaks of this disease are estimated to cost beekeepers from $300-$500 per colony. It is, therefore, very important to accurately diagnose outbreaks and seek management solutions. In this study, we analyzed samples from commercial beekeepers facing an outbreak of European foulbrood. Using standard microscopic analyses, a commercial lateral-flow device, and a genetic assay, we show that all three provide an accurate estimate of the presence of this disease. Where they differ could reflect novel variants of this important pathogen. This work sets the stage for more genetic analyses of this disease, an ongoing focus of ARS laboratories. Accurate diagnostics allow accurate treatment while preventing expensive colony losses and lost productive of pollinating honey bee colonies.

Technical Abstract: The western honey bee (Apis mellifera Linnaeus [Hymenoptera: Apidae) is susceptible to multiple pathogens. One of the most serious bacterial pathogens of honey bees is Melissococcus plutonius, the cause of the disease European foulbrood. European foulbrood disease is highly variable, with diverse outcomes at both the individual and colony levels, and it is often difficult to diagnose through visual inspection alone. Common lab diagnostic techniques include microscopic examination and molecular detection through PCR. In 2009, a lateral flow device was developed to allow for field diagnosis of European foulbrood. At the time it was developed and validated it was thought that M. plutonius was genetically homogenous. However, we have subsequently learned that this bacterium exists as multiple strains, including some strains that are classified as 'atypical´ for which the lateral flow device is potentially less effective. These devices are becoming more commonly used in the United States, though they have never been validated using strains from North America. It is essential to validate this device in multiple locations as different strains of M. plutonius circulate in different geographical regions. In this study we validate the field use of the lateral flow device compared to microscopic examination and PCR on larval samples from commercial honey bee colonies in the United States with visual signs of infection. We find high concurrence between the three diagnostic techniques, and that all three methods are highly sensitive for diagnosing European foulbrood.