RNAseq of Deformed Wing Virus and Other Honey Bee-Associated Viruses in Eight Insect Taxa with or without Varroa Infestation

Abstract

The global spread of a parasitic mite (Varroa destructor) has resulted in Deformed wing virus (DWV), a previously rare pathogen, now dominating the viromes in honey bees and contributing to large-scale honey bee colony losses. DWV can be found in diverse insect taxa and has been implicated in spilling over from honey bees into associated (“apiary”) and other (“non-apiary”) insects. Here we generated next generation sequence data from 127 insect samples belonging to diverse taxa collected from Hawaiian islands with and without Varroa to identify whether the mite has indirectly affected the viral landscapes of key insect taxa across bees, wasps, flies and ants. Our data showed that, while Varroa was associated with a dramatic increase in abundance of (predominantly recombinant) DWV in honey bees (and no other honey bee-associated RNA virus), this change was not seen in any other taxa sampled. Honey bees share their environment with other insect populations and exist as a homogenous group, frequently sharing common viruses, albeit at low levels. Our data suggest that the threat of Varroa to increase viral load in an apiary does not automatically translate to an increase in virus load in other insects living in the wider community.

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

“…as other studies using the same methodology have found a reduced DWV burden in resistant, not treated, managed populations in South Africa and Brazil [30]. [9], 2012 [29], 2012 * [17], 2015/16 [26] and 2019 (this study). 2012 and 2012 * could not be combined due to the different methodologies used.…”

“…Our results indicate a large proportion of RdRp sequences now contain those that match the DWV-B variant. This suggests that the Hawaiian Islands of Oahu and Big Island are transitioning from DWV-A to DWV-B dominance, mirroring that observed in the UK, USA, Europe, South Africa (Figure 2) [16,20,[28][29][30][31][32]. However, to confirm this would require future studies analyzing the full genome sequence of past and present samples from each island.…”

“…Intriguingly, the majority of change on Oahu appears to have occurred within the last three years, with samples from 2015 to 2016 consisting of mostly DWV-A (99% of reads) [ 26 ]. This is interesting because given the changing from DWV-A to DWV-B dominance overtime in other countries, one would expect the island which had hosted Varroa the longest, Oahu, to become dominated by DWV-B and to do so first.…”

“…In 2012, DWV-B was first detected in samples from Varroa -infested Hawaiian Islands [ 25 ] and again in 2016 [ 26 ]. Therefore, 10 years on from the original Hawaiian study that sampled 239 colonies detecting primarily DWV-A [ 9 ], we returned to resample three island populations.…”

Evaluating competition for forage plants between honey bees and wild bees in Denmark

“…We also do not specifically consider interactions between honey bees and other bees mediated via spread of shared pathogens or parasites. There is a net flow of diseases from honey bee apiaries into nearby populations of bumble bees, with possible negative spill-over to other wild bees [108][109][110][111][112]. Transmission of pathogens between species is thought to occur largely through shared flower use [113,114], thus, our analysis is likely to still identify wild bee species most at risk from being exposed to disease from honey bees [115], or the other direction, from wild bees to honey bees.…”