USDA, Agricultural Research Service, Bee Research Lab, Beltsville, MD, USA.
Sci Rep. 2019 Aug 27;9(1):12445. doi: 10.1038/s41598-019-47447-3.
Honey bees, the primary managed insect pollinator, suffer considerable losses due to Deformed wing virus (DWV), an RNA virus vectored by the mite Varroa destructor. Mite vectoring has resulted in the emergence of virulent DWV variants. The basis for such changes in DWV is poorly understood. Most importantly, it remains unclear whether replication of DWV occurs in the mite. In this study, we exposed Varroa mites to DWV type A via feeding on artificially infected honey bees. A significant, 357-fold increase in DWV load was observed in these mites after 2 days. However, after 8 additional days of passage on honey bee pupae with low viral loads, the DWV load dropped by 29-fold. This decrease significantly reduced the mites' ability to transmit DWV to honey bees. Notably, negative-strand DWV RNA, which could indicate viral replication, was detected only in mites collected from pupae with high DWV levels but not in the passaged mites. We also found that Varroa mites contain honey bee mRNAs, consistent with the acquisition of honey bee cells which would additionally contain DWV replication complexes with negative-strand DWV RNA. We propose that transmission of DWV type A by Varroa mites occurs in a non-propagative manner.
蜜蜂是主要的管理昆虫传粉媒介，但由于变形翅膀病毒（DWV）而遭受大量损失，DWV 是一种由螨 Varroa destructor 传播的 RNA 病毒。螨的传播导致了毒力 DWV 变体的出现。DWV 发生这种变化的基础还知之甚少。最重要的是，目前尚不清楚 DWV 是否在螨体内复制。在这项研究中，我们通过让螨以受感染的蜜蜂为食来使 Varroa 螨接触 DWV 型 A。在 2 天后，这些螨中的 DWV 载量显著增加了 357 倍。然而，在携带低病毒载量的蜜蜂蛹上再通过 8 天的传递后，DWV 载量下降了 29 倍。这种减少显著降低了螨将 DWV 传播给蜜蜂的能力。值得注意的是，仅在来自高 DWV 水平蛹的螨中检测到可能表示病毒复制的负链 DWV RNA，而在传代的螨中则没有检测到。我们还发现 Varroa 螨中含有蜜蜂 mRNA，这与螨获取了蜜蜂细胞一致，而蜜蜂细胞中还含有含有负链 DWV RNA 的 DWV 复制复合物。我们提出，Varroa 螨传播 DWV 型 A 的方式是非增殖性的。
