Doomed drones? Using passage experiments and mathematical modelling to determine Deformed wing virus population dynamics in male honeybees

Abstract

Varroa destructor is an ectoparasitic mite of honeybees which vectors a range of pathogenic viruses, the most notable being Deformed wing virus (DWV). Mites parasitise bees during pupal development and male honeybees, drones, have a longer development cycle than female workers (24 versus 21 days), allow for more progeny mites to develop per foundress (1.6–2.5 compared to 0.7–1.45). How this longer exposure time influences evolution of the transmitted virus population is unknown. Using uniquely tagged viruses recovered from cDNA we investigated the replication, competition and morbidity of DWV genotypes in drones. Assays examining virus replication and morbidity revealed drones are highly susceptible to both predominant genotypes of DWV. In virus passage studies using an equimolar inocula of major DNA genotypes and their recombinants, the recombinant form dominated but did not reach 100% of the virus population within 10 passages. Using an in-silico model of the virus–mite–bee system we examined bottlenecks during virus acquisition by the mite and subsequent injection of viruses into the host, which may play a significant role in shaping virus diversity. This study furthers our understanding of the variables influencing DWV diversity changes and provides insight into areas of future research in the mite–virus–bee system.

Shift in virus composition in honeybees ( Apis mellifera ) following worldwide invasion by the parasitic mite and virus vector Varroa destructor

“…Experimental injection of BQCV in honeybee pupae, mimicking varroa-mediated transmission, suggests that BQCV may be too virulent to develop an epidemically stable and successful virus-vector relationship with varroa at the colony and inter-colony levels [ 82 , 83 ]. Other factors, such as infection dose delivered by the mite, may be important to determine the nature of the association between the vector and the virus [ 84 ]. The apparent rise in prevalence and load of BQCV in presence of varroa mites might well be due to the suppressed immune response of bees as a consequence of varroa parasitism or infection by other viruses such as DWV [ 38 , 85 ].…”

Co-Occurrence of Wing Deformity and Impaired Mobility of Alates with Deformed Wing Virus in Solenopsis invicta Buren (Hymenoptera: Formicidae)

“…We are not aware of any sex-link between this virus and any other insect including ants. With regard to honey bees, a recent study by [33] (and the references therein) reported that emerging drones exhibited overt developmental deformities similar to those seen in the worker brood when injected with DWV as white-eyed pupae. They also reported that a percentage of drones without any outward deformities carried very high titer levels equivalent to drones with outward deformities.…”