The use of molecular biology and epidemiological techniques in managing and studying European foulbrood in honey bees

Abstract

European foulbrood (EFB) is a major bacterial disease infecting honey bees internationally, caused by the gram positive bacteria Melissococcus plutonius. This study aimed to gain more understanding of the spread of this disease in the UK using molecular and epidemiological methods. There is a multi-locus sequence typing (MLST) scheme that uses four genes to identify sequence types. Assigning a sequence type allows spread to be assessed. In the UK 72% of cases are made up of three sequence types spread across the country. More clarity within these sequence groups would allow outbreak clusters to be identified and managed. A cost-effective whole genome sequencing method was developed, and a single nucleotide polymorphism (SNP) analysis was performed on a selection of samples from naturally infected larval samples from England and Wales. This analysis showed clear outbreak clusters within the sequence types, that were geographically linked. From the same sequencing data, virulence and antimicrobial resistance genes were found. Some bacterial species act as secondary invaders following infection of M. plutonius. Whole genome sequencing data found genes from some of these species. One particular bacteria of interest found in some samples was Paenibacillus alvei a common secondary invader of M. plutonius. A survey was carried out in two areas with high cases of European Foulbrood, Somerset and Cambridgeshire, to assess what the beekeepers’ opinions were on why the disease was spreading. Structural equation modelling was used to investigate causes of disease spread. Overall, this study produced whole genome sequencing data that gave clarity to outbreaks, gave more genomic insight and used beekeeper’s opinions to assess the risks causing European foulbrood to spread.