Ryabov Eugene V, Posada-Florez Francisco, Rogers Curtis, Lamas Zachary S, Evans Jay D, Chen Yanping, Cook Steven C
United States Department of Agriculture - Agricultural Research Service, Bee Research Laboratory, Beltsville, MD, United States.
Department of Entomology, University of Maryland, College Park, MD, United States.
Front Insect Sci. 2022 Sep 23;2:931352. doi: 10.3389/finsc.2022.931352. eCollection 2022.
The ectoparasitic mite, and the viruses it vectors, including types A and B of Deformed wing virus (DWV), pose a major threat to honey bees, . Analysis of 256 mites collected from the same set of field colonies on five occasions from May to October 2021 showed that less than a half of them, 39.8% (95% confidence interval (CI): 34.0 - 46.0%), were able to induce a high (overt) level DWV infection with more than 10 viral genomes per bee in the pupa after 6 days of feeding, with both DWV-A and DWV-B being vectored at similar rates. To investigate the effect of the phoretic (or dispersal) stage on adult bees on the mites' ability to vector DWV, the mites from two collection events were divided into two groups, one of which was tested immediately for their infectiveness, and the other was kept with adult worker bees in cages for 12 days prior to testing their infectiveness. We found that while 39.2% (95% CI: 30.0 - 49.1%) of the immediately tested mites induced overt-level infections, 12-day passage on adult bees significantly increased the infectiousness to 89.8% (95% CI: 79.2 - 95.6%). It is likely that Varroa mites that survive brood interruptions in field colonies are increasingly infectious. The mite lifespan was affected by the DWV type it transmitted to pupae. The mites, which induced high DWV-B but not DWV-A infection had an average lifespan of 15.5 days (95% CI: 11.8 - 19.2 days), which was significantly shorter than those of the mites which induced high DWV-A but not DWV-B infection, with an average lifespan of 24.3 days (95% CI: 20.2 - 28.5), or the mites which did not induce high levels of DWV-A or DWV-B, with an average survival of 21.2 days (95% CI: 19.0 - 23.5 days). The mites which transmitted high levels of both DWV-A and DWV-B had an intermediate average survival of 20.5 days (95% CI: 15.1 - 25.9 days). The negative impact of DWV-B on mite survival could be a consequence of the ability of DWV-B, but not DWV-A to replicate in Varroa.
外寄生螨及其传播的病毒，包括变形翅病毒（DWV）的A、B型，对蜜蜂构成了重大威胁。对2021年5月至10月期间从同一组野外蜂群中五次采集的256只螨虫进行分析，结果显示，其中不到一半（39.8%，95%置信区间（CI）：34.0 - 46.0%）在喂食6天后，能够在蛹期使每只蜜蜂体内的病毒基因组超过10个，从而引发高水平（显性）的DWV感染，DWV - A和DWV - B的传播率相似。为了研究成年蜜蜂的携播（或扩散）阶段对螨虫传播DWV能力的影响，将两次采集的螨虫分为两组，一组立即检测其感染性，另一组与成年工蜂在笼中饲养12天，然后再检测其感染性。我们发现，立即检测的螨虫中有39.2%（95% CI：30.0 - 49.1%）引发了显性水平的感染，而在成年蜜蜂上经过12天的传播后，感染性显著增加至89.8%（95% CI：79.2 - 95.6%）。野外蜂群中在育雏中断后存活下来的瓦螨可能传染性越来越强。螨虫的寿命受其传播给蛹的DWV类型影响。引发高水平DWV - B但未引发DWV - A感染的螨虫平均寿命为15.5天（95% CI：11.8 - 19.2天），这明显短于引发高水平DWV - A但未引发DWV - B感染的螨虫，其平均寿命为24.3天（95% CI：20.2 - 28.5天），也短于未引发高水平DWV - A或DWV - B感染的螨虫，其平均存活时间为21.2天（95% CI：19.0 - 23.5天）。同时传播高水平DWV - A和DWV - B的螨虫平均存活时间为中间值，即20.5天（95% CI：15.1 - 25.9天）。DWV - B对螨虫存活的负面影响可能是由于DWV - B而非DWV - A能够在瓦螨体内复制。
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