Comparison of within hive sampling and seasonal activity of Nosema ceranae in honey bee colonies

Nosema ceranae is a microsporidian parasite of the European honey bee, Apis mellifera, that is found worldwide and in multiple Apis spp.; however, little is known about the effects of N. ceranae on A. mellifera. Previous studies using spore counts suggest that there is no longer a seasonal cycle for N. ceranae and that it is found year round with little variation in infection intensity among months. Our goal was to determine whether infection levels differ in bees collected from different areas of the hive and if there may be seasonal differences in N. ceranae infections. A multiplex species-specific real-time PCR assay was used for the detection and quantification of N. ceranae. Colonies were sampled monthly from September 2009–2010 by collecting workers from honey supers, the fringe of the brood nest, and the brood nest. We found that all bees sampled were infected with N. ceranae and that there was no significant difference in infection levels among the different groups of bees sampled (P = 0.74). However, significant differences in colony infection levels were found at different times of the year (P < 0.01) with the highest levels in April–June and lower levels in the fall and winter. While our study was only performed for one year, it sheds light on the fact that there may be a seasonality to N. ceranae infections. Being able to predict future N. ceranae infections can be used to better advise beekeepers on N. ceranae management.

Nosema ceranae levels observed throughout the 13 months of sampling. On the y-axis is the N. ceranae infection level and month is on the x-axis. Lower case letters indicate significant differences between samples from warmer months and upper case letters indicate significant differences between samples sampled from the colder months.Figure optionsDownload as PowerPoint slideHighlights
► Nosema ceranae was detected in all 13 months of sampling at varying levels.
► Nosema apis was only detected at low levels in January.
► N. ceranae levels did not differ between bees sampled in different parts of the hive.
► Significant differences in colony infection levels were observed through time.
► Significantly higher levels of N. ceranae were seen April–June.