Abstract
The dynamics of viruses are critical to our understanding of disease pathogenesis. Using honey bee Deformed wing virus (DWV) as a model, we conducted field and laboratory studies to investigate the roles of abiotic and biotic stress factors as well as host health conditions in dynamics of virus replication in honey bees. The results showed that temperature decline could lead to not only significant decrease in the rate for pupae to emerge as adult bees, but also an increased severity of the virus infection in emerged bees, partly explaining the high levels of winter losses of managed honey bees, Apis mellifera, around the world. By experimentally exposing adult bees with variable levels of parasitic mite Varroa destructor, we showed that the severity of DWV infection was positively correlated with the density and time period of Varroa mite infestation, confirming the role of Varroa mites in virus transmission and activation in honey bees. Further, we showed that host conditions have a significant impact on the outcome of DWV infection as bees that originate from strong colonies resist DWV infection and replication significantly better than bee originating from weak colonies. The information obtained from this study has important implications for enhancing our understanding of host‑pathogen interactions and can be used to develop effective disease control strategies for honey bees.
Highlights
The European honey bee, Apis mellifera L. (Hymenoptera: Apidae), plays a vital role in agro-ecosystems by assisting in the pollination of one-third of the world’s food crops
While the vast majority of the Deformed wing virus (DWV) infected bees appeared to be asymptomatic, DWV infection was found in every apiary investigated and in every month of the year during the study
DWV is one of the most common and prevalent viruses found in honey bees
Summary
The European honey bee, Apis mellifera L. (Hymenoptera: Apidae), plays a vital role in agro-ecosystems by assisting in the pollination of one-third of the world’s food crops. A survey of microbes in CCD-affected honey bee colonies showed a higher incidence of viruses [4,5,6], raising serious concerns about risks of virus infections and resulting in an urgent need for effective control strategies against viral diseases to safeguard the health of honey bees. The severe symptoms of DWV infections are associated with infestations of the parasitic mite, Varroa destructor Both laboratory and field studies showed that the Varroa mite is an effective vector of DWV by acquiring the virus from infected bees and transmitting it horizontally to uninfected bees during feeding [24,25,26,27,28,29,30,31], and an activator of the virus by causing host immunosuppression and thereby fostering viral replication in bees [32]. Gene expression levels of vitellogenin (Vg), a precursor of egg yolk protein that is a plausible marker of general robustness and nutritional status of honey bees, were compared in bees from both strong and weak colonies to examine the correlation between the host health status and the virus titer in honey bees
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