Ten Years of Deformed Wing Virus (DWV) in Hawaiian Honey Bees (Apis mellifera), the Dominant DWV-A Variant Is Potentially Being Replaced by Variants with a DWV-B Coding Sequence

Abstract

The combination of Deformed wing virus (DWV) and Varroa destructor is arguably one of the greatest threats currently facing western honey bees, Apis mellifera. Varroa’s association with DWV has decreased viral diversity and increased loads of DWV within honey bee populations. Nowhere has this been better studied than in Hawaii, where the arrival of Varroa progressively led to the dominance of the single master variant (DWV-A) on both mite-infested Hawaiian Islands of Oahu and Big Island. Now, exactly 10 years following the original study, we find that the DWV population has changed once again, with variants containing the RdRp coding sequence pertaining to the master variant B beginning to co-dominate alongside variants with the DWV-A RdRp sequence on the mite-infested islands of Oahu and Big Island. In speculation, based on other studies, it appears this could represent a stage in the journey towards the complete dominance of DWV-B, a variant that appears better adapted to be transmitted within honey bee colonies.

Epidemiology of a major honey bee pathogen, deformed wing virus: potential worldwide replacement of genotype A by genotype B

“…Understanding the dynamics of DWV genotypes within a population requires temporal sampling and DWV genotype-specific screening of that population at two or more time points. The published literature provides three cases: continental USA ( Ryabov et al, 2017 ), Hawaii ( Grindrod et al, 2021 ) and mainland United Kingdom ( Kevill et al, 2021 ). Here we complement these data with three new, independent, temporal datasets from mainland UK, Germany and northeast Italy.…”

“…DWV is also widespread among wild bee species and other flower-visiting insects ( Martin and Brettell, 2019 ; Nanetti et al, 2021 ), suggesting viral spillover from honey bees. Analogous to the worldwide spread of novel SARS-CoV-2 variants and their replacement of former variants in humans, evidence points to the worldwide spread of one DWV variant (genotype B) and its ongoing replacement of another, formerly prevalent DWV variant (genotype A) in the USA and UK ( Ryabov et al, 2017 ; Grindrod et al, 2021 ; Kevill et al, 2021 ), and potentially elsewhere ( Manley et al, 2019 ; see also Norton et al, 2021 ). Like SARS-Cov-2 and many other viruses, DWV represents a case of evolution in ecological time ( McMahon et al, 2018 ).…”

“…Since Ongus et al (2004) , DWV-B has been reported from a growing number of countries e.g. Israel ( Zioni et al, 2011 ), France ( Gauthier et al, 2011 ), and Germany ( Wilfert et al, 2016 ), and it appears to be increasing in prevalence on mainland USA ( Ryabov et al, 2017 ), Hawaii ( Grindrod et al, 2021 ) and the UK ( Kevill et al, 2021 ), potentially driving down DWV-A's prevalence. That DWV-A DWV-B recombinants have frequently been detected using ultradeep sequencing technologies ( Moore et al, 2011 ; Zioni et al, 2011 ; Wang et al, 2013 ; Ryabov et al, 2014 ; Dalmon et al, 2017 ; Barroso-Arévalo et al, 2019 ; Brettell et al, 2019 , 2020 ; Daughenbaugh et al, 2021 ) means that reporting of a genotype's prevalence on the basis of a small region of the viral genome, as often performed in qPCR-based studies, does not capture the full genetic diversity of a viral population and may obscure the role that recombination itself plays in competitive interactions among co-infecting viral genotypes.…”

Critical View on the Importance of Host Defense Strategies on Virus Distribution of Bee Viruses: What Can We Learn from SARS-CoV-2 Variants?

“…Either this variant has gone extinct, is replaced by or pushed back by other variants, or is only present in a very restricted geographical area [72]. The change in dominant variants of DWV is also documented in the UK and USA, where over the last 5 to 10 years the previously dominant DWV-A variant is being replaced by the DWV-B variant [73][74][75][76][77]. The underlying nature of this variant shift has not been fully clarified.…”

Varroa destructor from the Laboratory to the Field: Control, Biocontrol and IPM Perspectives—A Review

“…Varroa destructor spread also made an impact on the virus genetics and resulted in selection of virulent variants of DWV [ 87 , 88 , 89 ]. A particular DWV variant, namely DWV-B, infects the gut epithelium and salivary glands of the ecto-parasite [ 24 ], establishing it as a biological virus vector since it multiplies inside the vector [ 17 , 25 , 26 ].…”