Department of Entomology, National Chung-Hsing University, Taichung 402, Taiwan.
Department of Biotechnology and Animal Science, National Ilan University, Yilan 260, Taiwan.
J Invertebr Pathol. 2021 Nov;186:107687. doi: 10.1016/j.jip.2021.107687. Epub 2021 Oct 30.
Recent outbreaks of sacbrood virus (SBV) have caused serious epizootic disease in Apis cerana populations across Asia including Taiwan. Earlier phylogenetic analyses showed that cross-infection of AcSBV and AmSBV in both A. cerana and A. mellifera seems common, raising a concern of cross-infection intensifying the risk of disease resurgence in A. cerana. In this study, we analyzed the dynamics of cross-infection in three different types of apiaries (A. mellifera-only, A. cerana-only and two species co-cultured apiaries) over one year in Taiwan. Using novel, genotype-specific primer sets, we showed that SBV infection status varies across apiaries: AmSBV-AM and AcSBV-AC were the major genotype in the A. mellifera-only and the A. cerana-only apiaries, respectively, while AmSBV-AC and AcSBV-AC were the dominant genotypes in the co-cultured apiaries. Interestingly, co-cultured apiaries were among the only apiary type that harbored all variants and dual infections (i.e., AC and AM genotype co-infection in a single sample), indicating the interactions between hosts may form a conduit for cross-infection. The cross-infection between the two honey bee species appears to occur in a regular cycle with temporal fluctuation of AmSBV-AC and AcSBV-AC prevalence synchronized to each other in the co-cultured apiaries. Artificial infection of AcSBV in A. mellifera workers showed the suppression of viral replication, suggesting the potential of A. mellifera serving as a AcSBV reservoir that may contribute to virus spillover. Furthermore, the survival rate of A. cerana larvae was significantly reduced after artificial infections of both SBVs, indicating fitness costs of cross-infection on A. cerana and thus a high risk of disease resurgence in co-cultured apiaries. Our field and laboratory data provide baseline information that facilitates understanding of the risk of SBV cross-infection, and highlights the urgent need of SBV monitoring in co-cultured apiaries.
近年来，亚洲各地（包括台湾）的中华蜜蜂种群爆发了严重的 sacbrood 病毒（SBV）疫病。早期的系统进化分析表明，AcSBV 和 AmSBV 在中华蜜蜂和西方蜜蜂中交叉感染似乎很常见，这引起了人们的关注，即交叉感染可能会加剧中华蜜蜂疫病复发的风险。在这项研究中，我们在台湾的一年时间内，分析了三种不同类型的蜂场（仅西方蜜蜂、仅中华蜜蜂和两种蜜蜂混养蜂场）中的交叉感染动态。使用新型、基因型特异性引物集，我们表明 SBV 感染状况在蜂场之间存在差异：AmSBV-AM 和 AcSBV-AC 是仅西方蜜蜂和仅中华蜜蜂蜂场的主要基因型，而 AmSBV-AC 和 AcSBV-AC 是混养蜂场的主要基因型。有趣的是，混养蜂场是唯一一种存在所有变体和双重感染的蜂场类型（即单个样本中同时存在 AC 和 AM 基因型感染），这表明宿主之间的相互作用可能形成了交叉感染的途径。两种蜜蜂之间的交叉感染似乎呈周期性发生，AmSBV-AC 和 AcSBV-AC 的流行率在混养蜂场中相互同步波动。在西方蜜蜂工蜂中人工感染 AcSBV 后，病毒复制受到抑制，这表明西方蜜蜂可能成为 AcSBV 的储主，这可能导致病毒溢出。此外，人工感染两种 SBV 后，中华蜜蜂幼虫的存活率显著降低，这表明交叉感染对中华蜜蜂的适应性造成了成本，因此混养蜂场的疫病复发风险很高。我们的现场和实验室数据提供了基线信息，有助于理解 SBV 交叉感染的风险，并强调了在混养蜂场中进行 SBV 监测的迫切需要。
