The use of propolis for preventing and treating Nosema ceranae infection in western honey bee (Apis mellifera Linnaeus, 1787) workers

Abstract

The health of western honey bees (Apis mellifera L.) is constantly affected by Nosema ceranae, a microsporidian threat to colonies worldwide. We extracted propolis, a natural product exhibiting antimicrobial properties, from honey bee hives, fed it to worker bees before or after infection with N. ceranae, and determined its ability to protect bees from and treat them after infection. Protection from N. ceranae was tested using newly emerged bees that were group fed (50 bees/group) 50% propolis extract for 2, 4 and 8 d prior to infection with 1 × 105 spores per bee. Treatment of N. ceranae was tested on newly emerged bees that were individually force-fed with 2 µL of 50% (w/v) sucrose solution containing 1 × 105 spores per bee and then treated with 50% propolis in 50% sucrose solution (v/v) at 0, 2, 4 and 8 d post infection (p.i.). Positive (sugar water + N. ceranae), negative (sugar water only), and solvent (ethanol + sugar water) controls were included in both studies. Propolis fed to honey bees for 4 or 8 d before infection was associated with significantly reduced mortality, infectivity, and N. ceranae infection rates compared to the positive controls. Moreover, providing propolis to infected honey bees at d 0, 2, and 4 p.i. significantly reduced bee mortality, infection, and infectivity rates compared to the positive controls and bees treated 8 d p.i. Therefore, propolis extracted from honey bee hives may be a promising alternative approach to antibiotics for protecting colonies from Nosema disease.