SEASONAL VARIATIONS OF FOUR HONEY BEE VIRUSES IN PUPAE, HIVE AND FORAGER BEES OF CARNIOLAN GRAY BEE (APIS MELLIFERA CARNICA)

The seasonal dynamic of four honey bee viruses in 18 honey bee colonies from six selected apiaries were studied using a specific reverse transcriptase-polymerase chain reaction (RT-PCR) method. In each investigated colony, pupae, hive and forager bees were sampled and tested for acute bee paralysis virus (ABPV), chronic bee paralysis virus (CBPV), deformed wing virus (DWV) and black queen cell virus (BQCV) once per month during a 14 month-period. In pupae samples, only BQCV and DWV were found in very low percentages, with no major differences throughout the investigating period. In hive bees ABPV, BQCV, CBPV and DWV were detected, but in lower percentages than in foraging bees where the number of all four viruses was the highest. The BQCV was discovered in 100% of foraging bees and in 94% of hive bees. For the other viruses, seasonal differences were observed in hive bees and foraging bees; however, the highest seasonal variations were detected for ABPV. This study suggests that horizontal transmission of ABPV, BQCV and DWV may occur through contacts between social groups in the direction from forager to hive bees.