The Comparison of Honeybee Viral Loads for Six Honeybee Viruses (ABPV, BQCV, CBPV, DWV, LSV3 and SBV) in Healthy and Clinically Affected Honeybees with TaqMan Quantitative Real-Time RT-PCR Assays.

Laura Šimenc,Ivan Toplak,Tanja Knific

doi:10.3390/v13071340

Abstract

The viral loads of acute bee paralysis virus (ABPV), black queen cell virus (BQCV), chronic bee paralysis virus (CBPV), deformed wing virus (DWV), Lake Sinai virus 3 (LSV3), and sacbrood bee virus (SBV) were determined in samples with the use of quantitative TaqMan real-time reverse transcription and polymerase chain reaction (RT-qPCR). A total of 108 samples of healthy adult honeybees from four differently located apiaries and samples of honeybees showing different clinical signs of viral infections from 89 apiaries were collected throughout Slovenia. The aim of this study was to discover correlations between viral loads and clinical signs in adult honeybees and confirm previously set threshold viral load levels between healthy and clinically affected honeybees. Within this study, two new RT-qPCR assays for quantification of LSV3 and SBV were developed. Statistically significant differences in viral loads of positive samples were identified between healthy and clinically affected honeybees for ABPV, CBPV, DWV, and SBV, while for BQCV and LSV3, no statistical differences were observed between both groups. Despite high detected LSV3 prevalence and viral loads around 6.00 log10 viral copies/bee, this lineage probably has a limited impact on the health status of honeybee colonies. The determined viral loads between 3.94 log10 and 13.17 log10 in positive samples for six viruses, collected over 10 consecutive months, including winter, present additional information of high viral load variations in healthy honeybee colonies.

Highlights

Viruses are important pathogens of honeybees (Apis mellifera) frequently detected in commercial and hobby beekeeping apiaries, while different viruses can infect other wild pollinators, such as bumblebees, for which the pathogenicity of viral infections is still not fully understood [1,2,3,4]
Most honeybee viral infections might be present in subclinical form, in the combination of several factors, such as insufficient feeding of honeybee colonies, high varroa mite (Varroa destructor) infestations, or the presence of bacterial infections, the honeybee viruses can significantly contribute to honeybee losses [7]
One hundred and eight honeybee samples were collected from healthy honeybee colonies during 10 months of consecutive sampling

Summary

Introduction

Viruses are important pathogens of honeybees (Apis mellifera) frequently detected in commercial and hobby beekeeping apiaries, while different viruses can infect other wild pollinators, such as bumblebees, for which the pathogenicity of viral infections is still not fully understood [1,2,3,4]. More than 30 honeybee viruses have been identified and described using different molecular methods, including next-generation sequencing (NGS) [5,6]. Most honeybee viral infections might be present in subclinical form, in the combination of several factors, such as insufficient feeding of honeybee colonies, high varroa mite (Varroa destructor) infestations, or the presence of bacterial infections, the honeybee viruses can significantly contribute to honeybee losses [7].

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