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

John M K Roberts,Denis L Anderson,Peter A Durr

doi:10.1038/s41598-017-07290-w

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.

Highlights

Increased awareness of the importance of pollination for functional ecosystems and global food security has seen a surge in research into pollinator health and population declines[1, 2]
The expansion of V. destructor has significantly increased colony stress and elevated the importance of viruses in colony losses[11, 13, 17, 18]. This has led to increased understanding of the role of pathogenic viruses within colonies and identified deformed wing virus (DWV) as a major co-pathogen involved in colony losses in association with V. destructor[17, 18, 20,21,22]
In Region 2, Lake Sinai virus 1 (LSV1) and sacbrood virus (SBV) had equal highest prevalence in March 2014, while LSV1 was the most common virus in Region 1 and the only virus detected in Region 4, no viruses were found in 3 KUN samples that formed part of Region 4

Summary

Introduction

Increased awareness of the importance of pollination for functional ecosystems and global food security has seen a surge in research into pollinator health and population declines[1, 2]. The emergence of V. destructor has significantly altered the viral landscape in honeybee populations globally by increasing virus transmission and causing selection of more virulent virus strains[13,14,15,16]. The combination of V. destructor and viruses is considered the major cause of global colony losses[11, 13, 17, 18], but uncovering the importance of viruses alone remains a significant challenge due to the ubiquitous presence of V. destructor. DWV was only discovered following the spread of V. destructor, it is thought to exist naturally at low prevalence in all honeybee populations[14, 23] This hypothesis was recently tested following the arrival of V. destructor in Hawaii[14] and New Zealand[24], www.nature.com/scientificreports/. NGS technology has been applied in multiple insect systems for virus discovery[33,34,35,36,37,38] and presents a valuable tool for characterising the viral landscape of Australian honeybees

Methods

Results

Conclusion