The Spring Assessment of Nosema Spp. Infection in Honey Bee Colonies (Apis mellifera L.) - Sampling as an Important Aspect of a Reliable Diagnosis

The objective of the research was a comparative assessment of the infection levels of Nosema spp. in honey bees collected from different areas of the hive. A total of 588 honey bee colonies were sampled in spring (April-May) 2015 and 2016 through the simultaneous collection of dead worker bees from the bottom board of the hive and live bees from peripheral combs. A microscopic assay of composite samples of 60 bees was used for the detection and quantification of Nosema spp. spores. Consistent positive results of laboratory tests (detection of Nosema spp. spores in both live and dead bee samples) were achieved for 28% of colonies from surveyed group. In 36% of colonies both types of samples were Nosema-negative. Spores of Nosema spp. were detected solely in worker bees from the bottom board or exclusively in bees from nests in every 18% of sampled colonies. No differences were found between the share of colonies that had been identified as Nosema-infected on the basis of an analysis of only the live or dead bees (46% versus 46%). Laboratory examination of both types of bee samples can improve the reliability and accuracy of spore counting for the diagnosis of Nosema spp. infection in spring. The introduction of this sampling strategy in routine laboratory diagnostics can be considered as an alternative to the application of more sensitive PCR methods or sampling a higher number of live bees.