Risk factors associated with the abundance of Nosema spp. in apiaries located in temperate and subtropical conditions after honey harvest

Abstract

Nosema apis and Nosema ceranae are obligate parasites that develop within the honey bee gut reducing the life of theirhost. The role that they have in colony losses is not clear, and it remains to be elucidated how the geographical andseasonal variations influence pathogenicity of nosema. The aim of this study was to identify risk factors associated withthe abundance of Nosema spp. spores in apiaries located in temperate and subtropical regions after honey harvest. Atotal of 361 colonies distributed in five eco-regions of Argentina were examined to evaluate the abundance of Nosemaspp. spores. Regions differed with regard to temperature, precipitation, and vegetation landscape. The abundance ofNosema spp. spores was significantly higher in temperate than in subtropical regions. A south-north gradient of Nosemaspp. spore abundance was found, with the highest spore counts observed in South Santa Fe, continuously descendingtowards the northern regions of higher temperature. The observed gradient may be related to weather conditionsand/or availability of floral resources in each eco-region. Also, colonies with >3% of Varroa destructor infestation showedthe highest abundance of Nosema spp. spores. N. ceranae, N. apis, and co-infection were identified in 37.77, 26.66, and35.55% of the studied colonies, respectively.