Abstract
P>Two microsporidia species have been shown to infect Apis mellifera, Nosema apis and Nosema ceranae. This work present evidence that N. ceranae infection significantly suppresses the honey bee immune response, although this effect was not observed following infection with N. apis. Immune suppression would also increase susceptibility to other bee pathogens and senescence. Despite the importance of both Nosema species in honey bee health, there is no information about their effect on the bees' immune system and present results can explain the different virulence between both microsporida infecting honeybees.