Department of Biology, University of North Carolina at Greensboro, Greensboro, NC, United States of America.
Department of Agroecology, Aarhus University, Slagelse, Denmark.
PLoS One. 2018 Mar 29;13(3):e0195283. doi: 10.1371/journal.pone.0195283. eCollection 2018.
Deformed wing virus (DWV) is an important pathogen in a broad range of insects, including honey bees. Concordant with the spread of Varroa, DWV is present in the majority of honey bee colonies and can result in either low-level infections with asymptomatic bees that nonetheless exhibit increased colony loss under stress, or high-level infections with acute effects on bee health and viability. DWV can be transmitted vertically or horizontally and evidence suggests that horizontal transmission via Varroa is associated with acute symptomatic infections. Vertical transmission also occurs and is presumably important for the maintenance of DWV in honey bee populations. To further our understanding the vertical transmission of DWV through queens, we performed three experiments: we studied the quantitative effectiveness of vertical transmission, surveyed the prevalence of successful egg infection under commercial conditions, and distinguished among three possible mechanisms of transmission. We find that queen-infection level predicts the DWV titers in their eggs, although the transmission is not very efficient. Our quantitative assessment of DWV demonstrates that eggs in 1/3 of the colonies are infected with DWV and highly infected eggs are rare in newly-installed spring colonies. Additionally, our results indicate that DWV transmission occurs predominantly by virus adhering to the surface of eggs (transovum) rather than intracellularly. Our combined results suggest that the queens' DWV vectoring capacity in practice is not as high as its theoretical potential. Thus, DWV transmission by honey bee queens is part of the DWV epidemic with relevant practical implications, which should be further studied.
变形翅膀病毒（DWV）是一种广泛存在于昆虫中的重要病原体，包括蜜蜂。与瓦螨的传播相一致，DWV 存在于大多数蜜蜂群体中，可能导致无症状蜜蜂的低水平感染，尽管在压力下蜜蜂群体会有更高的损失，或者高水平感染会对蜜蜂健康和生存力产生急性影响。DWV 可以垂直或水平传播，有证据表明，通过瓦螨的水平传播与急性症状感染有关。垂直传播也会发生，并且可能对蜜蜂种群中 DWV 的维持很重要。为了进一步了解通过蜂王进行 DWV 的垂直传播，我们进行了三项实验：我们研究了垂直传播的定量效果，调查了商业条件下成功感染卵的流行率，并区分了三种可能的传播机制。我们发现，蜂王的感染水平可以预测其卵中的 DWV 滴度，尽管传播效率不是很高。我们对 DWV 的定量评估表明，在 1/3 的蜂群中，卵受到 DWV 的感染，而新安装的春季蜂群中高感染的卵很少。此外，我们的结果表明，DWV 传播主要是通过病毒附着在卵的表面（经卵）而不是细胞内进行的。我们的综合结果表明，蜂王在实践中的 DWV 传播能力不如其理论潜力那么高。因此，蜜蜂蜂王的 DWV 传播是 DWV 流行的一部分，具有相关的实际意义，应该进一步研究。
