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

Abstract

The most prevalent viral pathogen of honeybees is Deformed Wing Virus (DWV) and its two most widely studied and common master-variants are DWV-A and DWV-B. The prevalence of DWV variants in the UK and in the US is changing, with the prevalence of the DWV-A strain declining and DWV-B increasing over time. In 2012, only DWV-A was detected on the Hawaiian Islands of Oahu. In this study we focused on a colony-level survey of DWV strains in a single apiary and examined the prevalence of DWV variants over the course of two years. In 2018 and 2019, a total of 16 colonies underwent viral testing in January, May, and September. Of those 16 colonies, four were monitored in both 2018 and 2019. Individual colonies showed variability of DWV master variants throughout the sampling period. DWV-A was consistently detected; however, the detection of DWV-B was variable across time in individual colonies. Ultimately, this study demonstrated a seasonal variation in both viral prevalence and load for DWV-B, providing a perspective on the dynamic nature of DWV master variants emerging in Hawaii.

Selection and Multiplexing of Reverse Transcription–Quantitative PCR Tests Targeting Relevant Honeybee Viral Pathogens

“…The primers and probe systems previously described for the detection of honeybee viral pathogens ABPV, BQCV, DWVA, DWVB, CPBV and SBV [25,26,29,[31][32][33][34][35][36][37][38][39] were tested for their specificity and inclusivity by BLASTN (https://blast.ncbi.nlm.nih.gov/Blast.cgi, accessed on 27 April 2024) against 500 database entries. Those matching the highest number of sequences of the target virus were selected for use in one-step RT-qPCR tests with TaqMan probes.…”

“…Among these most common viruses, DWVB and CBPV have shown increasing prevalence in many geographical areas [ 9 , 21 , 22 , 23 , 24 , 25 ]. In particular, the relative representation of DWVB in thousands of RNAseq libraries for A. mellifera , Bombus terrestris and V. destructor increased after 2014 in the US and became dominant in Europe [ 24 ].…”

“…On the contrary, Norton et al [ 27 ] found evidence that the DWVB variant caused a lower mortality in honeybee pupae than DWVA and that it accumulated to higher levels. This might explain the increasing DWVB prevalence over DWVA reported in different countries [ 21 , 22 , 23 , 24 , 25 ]. Moreover, Kevill et al [ 23 ] reported that DWVA is transmitted by V. destructor , while DWVB is not.…”

“…The RT-qPCR-based methods available for the detection of ABPV, BQCV, CBPV, DWVA, DWVB and SBV are singleplex tests that use Sybr Green [ 25 , 26 , 29 , 31 , 32 , 34 , 35 , 36 , 37 , 38 ] or fluorescent-probe-based detection [ 33 , 39 , 40 , 41 , 42 ], but only two of these have been validated [ 6 , 40 ].…”

“…Most tests have already been applied in ecological studies and diagnostic screenings [ 4 , 9 , 25 , 43 , 44 , 45 , 46 , 47 , 48 ].…”