Effect of stingless bee propolis on experimental infection of dwarf honeybee Apis florea with Nosema ceranae

Introduction: Propolis collected by stingless bees from various types of plants has been used as an antimicrobial agent. We assessed the effect of propolis produced by a stingless bee, Trigona apicalis on Apis florea experimentally infected with Nosema ceranae. Materials &Methods: Each Nosema free-bee was fed 2 µl of 50% (w/v) sucrose solution containing with Nosema spores at dosages of 40,000 spores/bee and 0 as negative control (CO). Treated bees were provided with 10%, 20%, 50% and in 0% propolis (w/v) in water, defined as 10P, 20P, 50P and 0P. We assessed the effects of propolis 14 days later (post inoculation). Results: All treated bees had significantly higher survival than untreated bees. However, survival was lower than that of uninfected control bees. Bees treated with 50P had the highest survival rate. No CO bees became infected over the course of the study. However, infection rates of bees in 0P, 10P, 20P and 50P were 75%±1.4, 72%±5.6, 69%±4.2 and 47%±1.4 respectively. Infection rates between 0P and 10P were not statistically different. However, infection rates of 20P and 50P bees were significantly lower from those of 0P and 10P bees. The infection ratios of 50P and 20P were 28.5±3.5 3 and 37.5±2.12 cells. The highest infection ratio was found in 0P which were 89±8.48 cells. In addition, propolis-treated bees had hypopharyngeal glands with significantly higher protein content than CO bees. Conclusion & Discussion: Thus, N. ceranae may reduce protein production of honeybee hypopharyngeal glands and thereby shorten bee life span. Overall, propolis treatment significantly reduced Nosema infection rate and bee mortality.