Detection of a honeybee iflavirus with intermediate characteristics between kakugo virus and deformed wing virus

Iflavirus RNA was detected in honeybee colonies displaying unduly aggressive behavior and with no evidence of morphological alterations. Sequence analysis of the RNA-dependent RNA polymerase (RdRp) revealed that the iflavirus strain was more similar (> 99% aa) to Deformed Wing Virus (DWV), that has been associated with morphological alterations in bees, rather than to the newly-described Kakugo Virus (KV) (about 95% aa), that has been associated with increased aggressiveness. Therefore, the iflavirus strain detected in the Italian hives genetically resembled DWV but was apparently associated with a KV-like phenotype. RT-PCR detected the iflavirus RNA in the abdomen of the workers, and only in one case was the virus detected in the head. No viral RNA was detected in the drones, a pattern of virus distribution across the honeybee casts that is in apparent conflict with the higher rates of infestation of drones by the mite Varroa distructor. The identification of a virus with apparently intermediate features between DWV and KV open new perspectives on the patho-biological role of iflaviruses in honeybees.