Effect of the Parasitic Mite Varroa Destructor on the Immune System of Africanized and European Honey Bees at the Molecular and Cellular Levels
Varroa destructor parasitism of honeybees includes cuticle penetration and injection of saliva possibly containing immune-suppressing effectors. To replicate these effects on adults and pupae of European and Africanized honey bees, parasitism was compared to wounding, injecting buffer and injecting V. destructor homogenate. For both developmental stages and genotypes, wounding and injecting buffer increased expression of the TOLL and Imd immune pathway genes, defensin-1 and hymenoptaecin, but decreased expression of pUf68 (JAK/STAT immune pathway) and vitellogenin (longevity marker). However, the expressions of all genes studied decreased with homogenate injection similar to parasitism. For adults, haemocyte concentration and prophenol oxidase expression showed similar responses demonstrating similar effects on cellular and molecular immunity. Differences between European and Africanized honey bees, were much less than those observed between developmental stages. These results indicate that various aspects of V. destructor parasitism have different effects on immune responses, but the overall effect is immune suppression.