No abstract

This study was conducted to determine the prevalence and infection levels of the microsporidia fungi Nosema apis and/or Nosema ceranae in honey bee colonies of two Canadian provinces. Three surveys were conducted in the springs of 2008, 2010 and 2012 and PCR identification of Nosema species were performed in samples from 169 and 181 Ontario colonies and from 76 Alberta colonies that tested positive to Nosema spp. Infection levels of positive colonies were determined by microscopy and analyzed by Nosema spp. Results showed that N. ceranae was the dominant species in all three surveys (prevalence range of 41-91 vs. 4-34 % for N. apis), whereas mixed infections were less frequent than single infections (5-25 %). Infection levels of colonies parasitized by N. ceranae were three to five times higher than those of colonies parasitized by N. apis in the three surveys whereas mixed infections showed the highest spore counts. This is the first field study demonstrating significantly higher infection levels in colonies parasitized with either N. ceranae only or with both, N. ceranae and N. apis, than in colonies parasitized with N. apis only. Taken together, these results suggest that N. ceranae may be more virulent and better adapted than N. apis in cold climates such as Canadian environments.

Honey bee (Apis mellifera) grooming behavior is an important mechanism of resistance against the parasitic mite Varroa destructor. This research was conducted to study associations between grooming behavior and the expression of selected immune, neural, detoxification, developmental and health-related genes. Individual bees tested in a laboratory assay for various levels of grooming behavior in response to V. destructor were also analyzed for gene expression. Intense groomers (IG) were most efficient in that they needed significantly less time to start grooming and fewer grooming attempts to successfully remove mites from their bodies than did light groomers (LG). In addition, the relative abundance of the neurexin-1 mRNA, was significantly higher in IG than in LG, no groomers (NG) or control (bees without mite). The abundance of poly U binding factor kd 68 and cytochrome p450 mRNAs were significantly higher in IG than in control bees. The abundance of hymenoptaecin mRNA was significantly higher in IG than in NG, but it was not different from that of control bees. The abundance of vitellogenin mRNA was not changed by grooming activity. However, the abundance of blue cheese mRNA was significantly reduced in IG compared to LG or NG, but not to control bees. Efficient removal of mites by IG correlated with different gene expression patterns in bees. These results suggest that the level of grooming behavior may be related to the expression pattern of vital honey bee genes. Neurexin-1, in particular, might be useful as a bio-marker for behavioral traits in bees.