A novel strain of virus discovered in China specific to the parasitic mite Varroa destructor poses a potential threat to honey bees

Authors: CHEN, GONG WEN - Zhejiang University; WANG, SHUAI - Zhejiang University; JIA, SHUO - Zhejiang University; FENG, YE - Zhejiang University; HU, FU LIANG - Zhejiang University; Chen, Yanping - Judy; ZHENG, HUO QING - Zhejiang University

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2021
Publication Date: 4/15/2021
Citation: Chen, G., Wang, S., Jia, S., Feng, Y., Hu, F., Chen, Y., Zheng, H. 2021. A novel strain of virus discovered in China specific to the parasitic mite Varroa destructor poses a potential threat to honey bees. Viruses. 13(4):679. https://doi.org/10.3390/v13040679.
DOI: https://doi.org/10.3390/v13040679

Interpretive Summary: The parasitic Varroa mite is one of the most serious pests of honey bees worldwide because it not only feeds directly on honey bees but also serves as a vector for transmitting viruses among honey bees. Using advanced molecular technologies, we discovered a novel China strain of the virus, called Varroa destructor virus-2, which is specific to Varroa mites. The epidemiological investigation showed that the virus was highly prevalent among Varroa mite populations and was not identified in honey bees. Further bioassays showed that the virus could actually cause infection and replicate in honey bees under laboratory conditions, suggesting the possibility of the virus being transmitted to the honey bees during Varroa infestations and posing a potential threat to the health of honey bees. The information gained from this study should be of interest to researchers, graduate students, beekeepers and policymakers worldwide.

Technical Abstract: The ectoparasitic mite, Varroa destructor, feeds directly honey bees and serves as a vector for transmitting viruses among honey bees. The Varroa mite causes relatively little damage to its natural host, the Eastern honey bee (Apis cerana) but it is the most devastating pest for the Western honey bee (A. mellifera). Using Illumina HiSeq sequencing technology, we conducted a metatranscriptome analysis of the microbial community associated with Varroa mites. This study led to the identification of a novel Chinese strain of Varroa destructor virus -2 (VDV-2-China), which is a member of the Iflaviridae family and was previously reported to be specific to Varroa mites. A further epidemiological investigation showed that the virus was highly prevalent among Varroa populations and was not identified in any of the adult workers from both A. mellifera and A. cerana colonies distributed in six provinces in China, clearly indicating that the strain is predominantly a Varroa-adapted virus. While A. mellifera worker pupae exposed to a low level of Varroa mites tested negative for VDV-2-China, VDV-2-China was detected in 12.5% of the A. mellifera worker pupae that were parasitized by more than ten Varroa mites, bringing into play the possibility of a new scenario where VDV-2 could be transmitted to the honey bees during heavy Varroa infestations. Bioassay for the VDV-2-China infectivity showed that A. cerana was not a permissive host for VDV-2-China, yet A. mellifera could be a biological host that supports VDV-2-China's replication. The different replication dynamics of the virus between the two host species reflect their variation in terms of susceptibility to the virus infection, posing a potential threat to the health of the Western honey bee. The information gained from this study should be of interest to the researchers, graduate students, beekeepers and policymakers worldwide.