Accumulation and Competition Amongst Deformed Wing Virus Genotypes in Naive Australian Honeybees Provides Insight Into the Increasing Global Prevalence of Genotype B
Accumulation and Competition Amongst Deformed Wing Virus Genotypes in Naive Australian Honeybees Provides Insight Into the Increasing Global Prevalence of Genotype B
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DOI：
10.3389/fmicb.2020.00620
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发表时间：
2020-04-09
影响因子：
5.2
通讯作者：
Beekman, Madeleine
中科院分区：
文献类型：
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作者：
Norton, Amanda M.;Remnant, Emily J.;Beekman, Madeleine
蜂群死亡通常归因于外寄生螨瓦螨和由螨传播的变形翅病毒 (DWV)。在存在 V. destructor 的情况下，两种主要基因型（DWV-A 和 DWV-B）均与菌落损失相关。研究表明，DWV-B 是英国和欧洲最流行的基因型。最近，DWV-B 在美国的患病率有所增加。 DWV-B 的患病率不断增加，而 DWV-A 的患病率却不断上升，这表明基因型之间存在竞争。竞争可能是由于基因型之间毒力的差异、适应性的差异（例如复制率）或多种因素的组合造成的。在这项研究中，我们调查了 DWV 基因型在首次接触 V. destructor 和 DWV 的澳大利亚蜜蜂中的积累率是否有所不同，以及病毒载量是否与蜜蜂蛹的死亡率相关。我们用 DWV-A、DWV-B 和从耐受破坏弧菌的蜂群中分离出的重组菌株单独或共同感染蛹。我们监测了整个化蛹期间的病毒积累，直至注射后 192 小时。我们发现积累方面存在显着差异，其中 DWV-A 积累的负载量明显低于 DWV-B 和 DWV 重组体。我们还发现了竞争的证据，其中 DWV-B 负载在 DWV-A 存在的情况下显着减少，但仍然累积到总体最高负载。与之前的研究相比，我们发现注射 DWV-A 和 DWV-B 的蛹之间的毒力存在显着差异。与 DWV-B (0.4% +/- 0.33 SE) 和 DWV 重组 (2.2% +/- 0.83 SE) 注射相关的平均死亡率显着低于 DWV-A (11% +/- 1.2 SE) 观察到的平均死亡率。我们的结果表明，与 DWV-A 相比，感染 DWV-B 的蛹发育成成虫的比例更高。总体而言，我们的数据表明，蛹的低死亡率和 DWV-B 积累到相对于 DWV-A 更高负载的能力，即使在共同感染期间，可能有利于破坏弧菌的媒介传播，因此可能是全球 DWV-B 流行率不断上升的因素。
Honeybee colony deaths are often attributed to the ectoparasitic mite Varroa destructor and deformed wing virus (DWV), vectored by the mite. In the presence of V. destructor both main genotypes (DWV-A and DWV-B) have been correlated with colony loss. Studies show that DWV-B is the most prevalent genotype in the United Kingdom and Europe. More recently DWV-B has increased in prevalence in the United States. The increasing prevalence of DWV-B at the expense of DWV-A suggests that competition exists between the genotypes. Competition may be due to disparities in virulence between genotypes, differences in fitness, such as rate of replication, or a combination of factors. In this study we investigated if DWV genotypes differ in their rate of accumulation in Australian honeybees naive to both V. destructor and DWV, and if viral load was associated with mortality in honeybee pupae. We singly and co-infected pupae with DWV-A, DWV-B, and a recombinant strain isolated from a V. destructor tolerant bee population. We monitored viral accumulation throughout pupation, up to 192 h post-injection. We found significant differences in accumulation, where DWV-A accumulated to significantly lower loads than DWV-B and the DWV-recombinant. We also found evidence of competition, where DWV-B loads were significantly reduced in the presence of DWV-A, but still accumulated to the highest loads overall. In contrast to previous studies, we found significant differences in virulence between pupae injected with DWV-A and DWV-B. The average mortality associated with DWV-B (0.4% +/- 0.33 SE) and DWV-recombinant (2.2% +/- 0.83 SE) injection were significantly less than observed for DWV-A (11% +/- 1.2 SE). Our results suggest that a higher proportion of DWV-B infected pupae will emerge into adults, compared to DWV-A. Overall, our data suggest that low mortality in pupae and the ability of DWV-B to accumulate to higher loads relative to DWV-A even during co-infection may favor vector transmission by V. destructor, and may thus be contributing factors to the increasing prevalence of DWV-B globally.