The health of honey bees, which play a pivotal role in agriculture and ecosystems, is increasingly jeopardized by viral infections, particularly those caused by the deformed wing virus (DWV). Recent findings indicate a significant shift as genotype B of DWV and its related recombinant viruses have become the dominant strains among honey bee colonies throughout Europe.
Previously regarded as less severe, DWV has transformed from being considered merely a stressor to one of the leading causes of winter mortalities among honey bee populations. The primary vector for this virus, the Varroa destructor mite, was first introduced to Europe around the mid-20th century; since then, it has facilitated the rampant spread of DWV among honey bees. The pathogenicity of DWV has escalated, posing severe risks to colony survival.
A comprehensive study conducted across 15 European countries between 2010 and 2017 highlighted the increasing prevalence of DWV-B over the historical strain, DWV-A. The research team utilized real-time PCR methods and RNA sequencing technology to quantify and analyze the distribution of these viral genotypes among individual bees and samples collected from colonies.
The findings revealed DWV-B not only outnumbering DWV-A significantly but also exhibiting higher viral loads, particularly under conditions infected by the Varroa mite. "We found DWV-B was detected more frequently and at higher loads than DWV-A across many European countries," stated the authors of the article, affirming the grave implication of the shift.
One of the study's pivotal moments was the identification of recombinants, hybrids formed through co-infections, which emerged prominently from the interactions of DWV-A and DWV-B. The analysis indicated these recombinant viruses were clustered around specific genomic areas, potentially heightening their virulence. The authors also remarked, "Recombination appears not random but clustered at defined genomic locations, which may affect the virulence of these viruses."
While DWV-B is now the most prevalent strain, DWV-A has not disappeared completely; it is sometimes detected at low levels, particularly in certain regions. For example, it still showed higher viral loads in colonies located in Moldova and Romania, leading researchers to suggest, "The prevalence of DWV-A was still common; it suggests we are observing a transitional phase." This complex interaction points to both strains adapting to their shared host under varied environmental pressures.
Overall, researchers concluded the urgent need for beekeeping communities to monitor these changes closely and adapt management practices accordingly. The increasing virulence of DWV-B poses significant challenges, particularly as bee populations around the globe face other stressors such as habitat loss and pesticide exposure. With both DWV and Varroa contributing to reduced colony stability, continuous investment and research are imperative for the preservation of honey bee health.
Understanding the genetic dynamics of DWV is central to future efforts aimed at mitigating its impact on both wild and domesticated honey bees. Continued surveillance and research are necessary to understand how these viruses function, replicate, and influence bee health moving forward.