Effects of larval Nosema ceranae infection on adult honey bee (Apis mellifera) morphology and physiology

Nosema ceranae is an important honey bee pathogen that has been implicated in CCD. Until recently, it was thought to be exclusively a disease of adult bees, but recent findings indicate that it can also infect larvae. Thus, little is known about the effects of larval Nosema infection. Vitellogenin (Vg) is a key protein necessary for egg-laying, production of brood food, proper immune function, and promotion of longevity through the reduction of oxidative stress. In worker bees, Vg increases in bees of nursing age, at approximately 7 days of age. We therefore investigated the effects of larval Nosema infection on hemolymph Vg and total protein concentration. Larvae infected by a high dose of Nosema ceranae spores developed into adults with 2 fold higher Vg titers. However, they also had 1.3 fold lower total hemolymph protein titers. Thus, Nosema infection resulted in a corresponding 1.7 fold increase in percentage Vg compared to control. Infected bees also had 1.1 fold fewer barbs than did control bees and, we found an inverse relationship between Vg and the number of barbs per lancet. Overall, adult infected bees were not significantly different from controls. Our results indicate that larval N. ceranae infection has a greater impact than does adult infection on adult honey bees. Overall, Nosema ceranae accelerates aging and causes infected bees to resemble older workers or queens