Abstract
The pathogenesis of varroasis has not been fully explained despite intensive research. Earlier studies suggested that parasitic infections caused by Varroa destructor mites were accompanied by immunosuppression in the host organism. The objective of this study was to analyse the influence of varroasis on one of the immune pathway in Apis mellifera measured by the expression of the prophenoloxidase (proPO) gene and the enzymatic activity of this gene’s product, phenoloxidase (EC 1.14.18.1). An evaluation was done of five developmental stages of honey bee workers and drones. The relative expression of proPO decreased in infected individuals. The only exceptions were worker prepupae (PP) and drone pupae with brown eyes and dark brown thorax (P5) where propo gene expression was 1.8-fold and 1.5-fold higher, respectively, than in the control. Phenoloxidase (PO) activity was 2.8-fold higher in infected pp workers and 2-fold higher in p5 drones in comparison with uninfected bees. Phenoloxidase activity was reduced in the remaining developmental stages of infected workers and drones. The relative expression of proPO was positively correlated with the relative PO activity in both workers (r = 0.988) and drones (r = 0.996). The results of the study indicate that V. destructor significantly influences the phenoloxidase-dependent immune pathway in honey bees.