Moku virus detection in honey bees, Belgium, 2018

The threat of honey bee RNA viruses to yellow-legged hornets: Insights from cross-species transmission events

Viral diseases are a significant challenge in beekeeping, and recent studies have unveiled a potential link between these diseases and the yellow-legged hornets (Vespa velutina), notorious predators of honey bees. However, it remains unclear whether virus diseases are commonly shared between honey bees and hornets or are merely sporadic cross-species transmission events. To address this knowledge gap, we conducted a study utilizing hornet-keeping practices in Yunnan, Southwest China. Our findings demonstrate that deformed wing virus (DWV-A) and Israeli acute paralysis virus (IAPV) can be transmitted from honey bees to yellow-legged hornets. We detected virus replication in various hornet stages, including pupae with IAPV infections, indicating the similarities between infected hornet and honey bee stages. Furthermore, we observed signs and infection intensities of DWV-A and IAPV comparable to those in honey bees. While different polymorphisms were found in the virus isolates from yellow-legged hornets, the sequences remain similar to honey bee counterparts. While our findings suggest that DWV-A and IAPV behave like common diseases, we observed a natural elimination of the viruses in hornet colonies, with minimal alterations in viral sequences. Consequently, these events appear to be cross-species transmission from honey bees, with yellow-legged hornets acting as potential incidental hosts. Further investigations of virus monitoring in hornets promise valuable insights into the disease ecology of bee-infecting viruses.

Viral load, not food availability or temperature, predicts colony longevity in an invasive eusocial wasp with plastic life history

Social insect colonies exhibit a variety of life history strategies, from the annual, semelparous colonies of temperate bees and wasps to the long-lived colonies of many ants and honeybees. Species introduced to novel habitats may exhibit plasticity in life history strategies as a result of the introduction, but the factors governing these changes often remain obscure. Vespula pensylvanica, a yellowjacket wasp, exhibits such plasticity in colony longevity. Multi-year (perennial) colonies are relatively common in introduced populations in Hawaii, while source populations in the western United States are typically on an annual cycle. Here, we use experiments and observational data to examine how diet, disease, nest thermal environment, and nest location influence colony longevity in a population with both annual and perennial colonies. Counter to our predictions, experimental feeding and warming did not increase colony survival in the winter in the introduced range. However, Moku Virus load and wasp colony density predicted colony survival in one year, suggesting a potential role for disease in modulating colony phenology. We also found that local V. pensylvanica colony density was positively correlated with Moku Virus loads, and that Arsenophonus sp. bacterial loads in V. pensylvanica colonies were positively associated with proximity to feral honeybee (Apis mellifera) hives, suggesting potential transmission routes for these poorly understood symbionts. The factors influencing colony longevity in this population are likely multiple and interactive. More important than food availability, we propose winter precipitation as a critical factor that may explain temporal and spatial variation in colony longevity in these invasive wasps.