Milbrath, M. O. | Search bioRxiv

bioRxiv2025

Everything, everywhere, all at once - Surveillance and molecular epidemiology reveal Melissococcus plutonius is endemic among Michigan, US beekeeping operations of all sizes and present in some honey bee colonies year-round

European foulbrood (EFB) is a severe bacterial disease of honey bee brood often leading to significant declines in colony health and honey production. The dearth of data on this disease in the United States (US) complicates response efforts. In this study, we combine surveillance and molecular epidemiology to investigate prevalence, diversity, and transmission dynamics of Melissococcus plutonius, the causative agent of EFB, in US honey bee colonies. Rates of infection and disease were found to be seasonal, with prevalence peaking in June when over half the colonies screened were infected. Whole genome, single nucleotide polymorphism analysis revealed wide genetic diversity even within a single hive. Operations often had multiple genotypes present which varied from year to year, consistent with high rates of transmission and reinfection. Prevalence and whole genome data provided here will be critical in tracking the efficacy of mitigation efforts and underscore the necessity of additional epidemiological investigations.

genomics↗

bioRxiv2024

Sacbrood viruses and select Lake Sinai virus variants dominated Apis mellifera colonies symptomatic for European foulbrood

European foulbrood (EFB) is a prevalent disease of the European honey bee (Apis mellifera) in the US, which can lead to colony decline and collapse. The bacterial components of EFB are well studied, but the diversity of viral infections within infected colonies has not been explored. Here we use meta-transcriptomics sequencing of 12 honey bee hives, symptomatic (+) and asymptomatic (-) for EFB to explore viral infection associated with the disease. We identified 41 viral genomes, belonging to two families, with a predominant occurrence of 34 genomes observed in colonies with severe EFB. This is in contrast to fewer, and a complete absence of Dicistroviridae genomes, recovered from healthy colonies (7 genomes). Identified viruses included multiple lineages previously reported in honey bees, namely Lake Sinai virus, Deformed wing virus, Sacbrood virus, Black queen cell virus, and Israeli acute paralysis virus. We observed specific Lake Sinai virus clades associated exclusively with EFB+ or EFB-colonies, in addition to EFB-afflicted colonies that exhibited an increase in relative abundance of sacbrood viruses. Multivariant analyses highlighted that a combination of site and EFB disease status influenced RNA virome composition, while EFB status alone didnt significantly impact it, presenting a challenge for comparisons between colonies kept in different yards. These findings contribute to the understanding of viral dynamics in honey bee colonies compromised by EFB and underscore the need for future investigations to consider viral composition when investigating EFB. ImportanceThis study on the viromes of honey bee colonies affected by European foulbrood (EFB) sheds light on the dynamics of viral populations in bee colonies in the context of a prevalent bacterial brood disease. The identification of distinct Lake Sinai virus and Sacbrood virus clades associated with colonies with severe EFB suggests a potential connection between viral composition and disease status, emphasizing the need for further investigation into the role of viruses during EFB infection. The observed increase in sacbrood viruses during EFB infection implies a possible viral dysbiosis, with potential implications for honey bee brood health. These findings contribute valuable insights for apicultural practices, offering a foundation for future research aimed at understanding and mitigating the impact of bacterial and viral infection in commercial honey bee operations and the management of EFB.

molecular biology↗