Absence of deformed wing virus and Varroa destructor in Australia provides unique perspectives on honeybee viral landscapes and colony losses

Abstract

Honeybee (Apis mellifera) health is threatened globally by the complex interaction of multiple stressors, including the parasitic mite Varroa destructor and a number of pathogenic viruses. Australia provides a unique opportunity to study this pathogenic viral landscape in the absence of V. destructor. We analysed 1,240A. mellifera colonies across Australia by reverse transcription-polymerase chain reaction (RT-PCR) and next-generation sequencing (NGS). Five viruses were prevalent: black queen cell virus (BQCV), sacbrood virus (SBV), Israeli acute paralysis virus (IAPV) and the Lake Sinai viruses (LSV1 and LSV2), of which the latter three were detected for the first time in Australia. We also showed several viruses were absent in our sampling, including deformed wing virus (DWV) and slow bee paralysis virus (SBPV). Our findings highlight that viruses can be highly prevalent in A. mellifera populations independently of V. destructor. Placing these results in an international context, our results support the hypothesis that the co-pathogenic interaction of V. destructor and DWV is a key driver of increased colony losses, but additional stressors such as pesticides, poor nutrition, etc. may enable more severe and frequent colony losses to occur.

Accumulation and Competition Amongst Deformed Wing Virus Genotypes in Naïve Australian Honeybees Provides Insight Into the Increasing Global Prevalence of Genotype B

“…We collected approximately 650 white-eyed pupae per colony, from capped brood cells of three unrelated A. mellifera colonies kept at the University of Sydney's apiary. These colonies are naïve to both V. destructor and DWV, neither of which are established in Australia (Roberts et al, 2017). Pupae that showed signs of melanization or damage from uncapping were excluded from the assay prior to injection.…”

“…V. destructor parasitism is particularly destructive to A. mellifera (hereafter simply honeybees), and is associated with significant colony losses. Australia is currently the only major beekeeping country to remain free from V. destructor (Oldroyd, 1999;Roberts et al, 2017).…”

“…DWV is a single-stranded positive sense RNA virus belonging to the Iflaviridae family. Prior to the spread of V. destructor, DWV was rarely detected whereas now the virus is found in virtually all honeybee populations worldwide, excluding Australia (Roberts et al, 2017). In some Varroa-free honeybee populations, DWV has been shown to have low prevalence and accumulate to very low levels (Martin et al, 2012;Ryabov et al, 2014;Shutler et al, 2014;McMahon et al, 2016).…”

De novoassembly, characterization, functional annotation and expression patterns of the black tiger shrimp (Penaeus monodon) transcriptome

“…As essentially all DWV-like genome sequence reads in this study originated from the stomach of a single individual shrimp, they were potentially derived from a virus-infected honeybee or mite-infested honeybee ingesting by this shrimp. While honeybees infested with Varroa mites have been detected recently in North Queensland not far from where the shrimp was collected 72 , DWV itself has not been detected in a comprehensive recent study 73 .The present study therefore represents the first detection of a DWV-like genome in Australia, although the origin remains unknown. This reinforces both the strength of the technology in detecting unknown pathogens and also the potential difficulty in interpretation of transcriptome results.…”

Identification of new viruses specific to the honey bee mite Varroa destructor

“…destructor is by far the most important in many cases (Roberts et al 2017). The damage caused by the mite is a result of the combined effect of direct feeding on the fat body of immature and adult bees (Ramsey et al 2019) and the transmission of an extensive set of viruses that infect and debilitate them (McMenamin and Genersch 2015).…”