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Everything, everywhere, all at once - Surveillance and molecular epidemiology reveal Melissococcus plutonius is
Peter D Fowler1, Upasana Dhakal2, Jeff H Chang2
1Comparative Medicine and Integrative Biology, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, United States of America.
Abstract:
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 2021 and 2022 we conducted a two-year cross-sectional surveillance study among Michigan beekeepers to establish baseline pathogen and disease prevalence. We combined this surveillance with molecular epidemiology to investigate genetic diversity, and transmission dynamics of Melissococcus plutonius, the causative agent of EFB, in US honey bee colonies. PCR screening detected M. plutonius in all 15 migratory and stationary beekeeping operations and in 6 of 14 hobby beekeeping operations. Infection and disease were found to be seasonal, with prevalence of both peaking in June when over half the colonies were infected, and over 20% had clinical EFB. 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.
Insights
European foulbrood (EFB) is a widespread honey bee disease in the US. Surveillance revealed high pathogen prevalence and genetic diversity of Melissococcus plutonius, indicating frequent transmission and reinfection.
Area of Science:
- Veterinary Entomology
- Apiculture Science
- Microbial Pathogenesis
Background:
- European foulbrood (EFB) significantly impacts honey bee colony health and honey production.
- Limited data on EFB prevalence in the US hinders effective disease management strategies.
Purpose of the Study:
- Establish baseline prevalence of EFB and its causative agent, Melissococcus plutonius, in US honey bee colonies.
- Investigate the genetic diversity and transmission dynamics of M. plutonius within US apiaries.
Main Methods:
- Conducted a two-year cross-sectional surveillance study in Michigan beekeeping operations.
- Utilized Polymerase Chain Reaction (PCR) screening for M. plutonius detection.
- Performed whole-genome single nucleotide polymorphism (SNP) analysis to assess genetic diversity and transmission.
Main Results:
- M. plutonius was detected in all surveyed migratory and stationary beekeeping operations.
- Infection and clinical EFB prevalence peaked in June, affecting over half and 20% of colonies, respectively.
- High genetic diversity of M. plutonius was observed within hives, with multiple genotypes present and varying yearly.
Conclusions:
- The study highlights the pervasive presence and seasonal nature of EFB in US honey bee colonies.
- Wide genetic diversity and year-to-year genotype variation suggest high transmission and reinfection rates.
- Collected data are crucial for monitoring mitigation strategies and emphasize the need for further epidemiological research.
