Characterization of Melissococcus plutonius strains in Michigan honey bees

View the project final report

Commodities

Practices

• Animal Production: animal protection and health, preventive practices
• Crop Production: pollination
• Education and Training: workshop

The health of honey bees is integral to sustainable crop production. European foulbrood (EFB) is a bacterial disease that severely affects the health of honey bees. For years, Michigan beekeepers have complained of high levels of this disease in their colonies. Our previous work shows that EFB is widespread in commercial colonies in Michigan, but many basic epidemiological questions regarding this pathogen remain unanswered. In 2019, in collaboration with the USDA ARS laboratory in Beltsville, MD, we were able to test samples from 78 honey bee colonies in Michigan managed by three commercial beekeepers. The purpose of this previous work was to validate a lateral flow test that can help diagnose EFB in the field. While we were able to confirm the sensitivity of the field test, there were multiple samples that showed a high bacterial load that tested negative by this device. Recent studies suggest that strain type may impact test results, but this has not been well studied, and nothing has yet been published on strain types in Michigan. Here we propose to use an established method for identifying strain types to identify the strains present in each of the 78 colonies. We hypothesize that the highly virulent atypical strain will be present in the false negatives, as there have been reports that this test may not be as sensitive in detecting these strains. We further hypothesize that multiple strains are circulating regionally and may be linked to travel. The results of this study will help us understand the impact strain type has on test results. Additionally it will give some basic information about what strain types are present among the sampled colonies. This is important as different strain types have been shown to have different levels of virulence for honey bees, and strain typing provides an important basis for future epidemiological study. Healthy honey bees are an important component of Michigan’s agriculture system, and understanding their diseases will benefit both beekeepers and the farmers that depend on them for pollination.

This project will have measurable impacts on multiple stakeholders.  Beekeepers will, for the first time, know what strains of M. plutonius are present in Michigan. The 38 strains that have so far been identified vary widely in their levels of virulence, with some causing no observable disease and others causing extremely high colony mortality. This makes understanding what strains are circulating important in formulating and prioritizing response and treatment protocols.

Veterinarians will also benefit from this project. Recent regulations have required veterinary oversight in order for beekeepers to treat their hives. Many veterinarians are not experienced in diagnosing EFB, making rapid tests that can be deployed in the field an important part of disease management. The results of this study will help veterinarians and beekeepers better understand the results of this test. If a false negative is suspected, the results of this research can help explain why, and inform when treatment is necessary.

Apiary inspectors will also have additional insight into possible causes for varying disease prevalence and severity between and within operations. It will also give them tools to better understand between apiary transmission and insights into transmission that might be associated with out of state travel. 

Finally, fruit and vegetable growers depend heavily on a healthy honey bee population for pollination services. Helping understand this disease is the first step to creating sustainable approaches to disease management that will positively impact honey bee health and increase the economic return of crops that depend on them for pollination.