Transmission of deformed wing virus between Varroa destructor foundresses, mite offspring and infested honey bees

Abstract

Background Varroa destructor is the major ectoparasite of the western honey bee (Apis mellifera). Through both its parasitic life-cycle and its role as a vector of viral pathogens, it can cause major damage to honey bee colonies. The deformed wing virus (DWV) is the most common virus transmitted by this ectoparasite, and the mite is correlated to increased viral prevalence and viral loads in infested colonies. DWV variants A and B (DWV-A and DWV-B, respectively) are the two major DWV variants, and they differ both in their virulence and transmission dynamics. Methods We studied the transmission of DWV between bees, parasitic mites and their offspring by quantifying DWV loads in bees and mites collected in in vitro and in situ environments. In vitro, we artificially transmitted DWV-A to mites and quantified both DWV-A and DWV-B in mites and bees. In situ, we measured the natural presence of DWV-B in bees, mites and mites’ offspring. Results Bee and mite viral loads were correlated, and mites carrying both variants were associated with higher mortality of the infected host. Mite infestation increased the DWV-B loads and decreased the DWV-A loads in our laboratory conditions. In situ, viral quantification in the mite offspring showed that, after an initially non-infected egg stage, the DWV-B loads were more closely correlated with the foundress (mother) mites than with the bee hosts. Conclusions The association between mites and DWV-B was highlighted in this study. The parasitic history of a mite directly impacts its DWV infection potential during the rest of its life-cycle (in terms of variant and viral loads). Regarding the mite’s progeny, we hypothesize that the route of contamination is likely through the feeding site rather than by vertical transmission, although further studies are needed to confirm this hypothesis. Graphical Abstract

Shift in virus composition in honeybees ( Apis mellifera ) following worldwide invasion by the parasitic mite and virus vector Varroa destructor

“…This confirms similar findings from local field surveys in Hawaii [17,52] and the Channel Islands [68], where varroa-free colonies were also still present at the time of sampling. Experimental work has demonstrated that the new route of transmission provided by the mite-the direct injection of the virus into honeybee pupae instead of oral transmission in adults, coupled with an immune-suppressive effect of the mite [38]-has promoted very high viral loads and the rapid spread of the disease [69][70][71][72][73]. In the two regions where we surveyed for DWV-B, Canada and the British Isles, this emerging DWV variant was still only rarely detected, relative to DWV-A, when these samples were collected in 2010-2013.…”

Prevalence and genome features of lake sinai virus isolated from Apis mellifera in the Republic of Korea

“…These mites have been implicated as a vector in the transmission of various viruses in honeybees, such as Israeli acute paralysis virus, deformed wing virus, Kashmir bee virus, V . destructor virus-1, black queen cell virus, and LSV [ 4 , 15 , 35 , 41 – 43 ]. This study showed the presence of LSV2 and LSV3 in V .…”

Seasonal Variability in the Prevalence of DWV Strains in Individual Colonies of European Honeybees in Hawaii

“…However, in our study, results clearly showed how a colony can test positive for a single DWV strain only to reverse to a different one in the next sampling period and colonies frequently tested positive for both strains during our study indicating simultaneous infections. The sequential changes and reversal in strain dominance in DWV we observed may be due to a few factors, including the genetic differences between A and B strains in Hawaii, coupled with the multiple routes of virus acquisition by bees within the hive, including food resources, vertical, horizontal, and finally, varroa mite replication and transmission [13,25,31].…”