|LI, WENFENG - Zhejiang University|
|SU, SONGKUN - Fujian Agricultural & Forestry University|
|Chen, Yanping - Judy|
Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2017
Publication Date: N/A
Interpretive Summary: Nosema disease has often been linked to honey bee colony losses worldwide. We conducted studies to compare Nosema infections in different developmental stages of adult workers and their respective immune responses under field conditions. The studies showed that Nosema spore loads varied among different stages of adult workers within the same colonies. While no Nosema infection was detected in emergent bees and nurses had a medium spore load, the foragers had the highest level of Nosema spore load and highest level of immune responses, suggesting that Nosema infection in the honey bee host depends upon the age of adult workers. This research adds important information to the Nosema disease prevention and management and will be of interest to the beekeeping community at large.
Technical Abstract: Nosema ceranae, a microsporidia parasite originally found in Asian honey bees, Apis cerana, causes widespread infection in adult workers of European honey bees, Apis mellifera, and has often been linked to honey bee colony losses worldwide. Previous investigations of the host immune response to N. ceranae infection were based on experimental inoculation of honey bee samples. However, little is known about the immune responses of honey bees that are naturally infected by N. ceranae. Here we compared natural infections of N. ceranae in three developmental stages of adult bees (newly emerged bees, nurses, and foragers) and their respective immune responses. Our studies showed that the Nosema spore load and infection prevalence varied among the different types of adult workers, and both of them increased as honey bees aged: No infection was detected in emergent bees, nurses had a medium spore load and prevalence, while foragers were with the highest Nosema infection level and prevalence. Quantification of the gene expression of antimicrobial peptides and microbial recognition proteins of Toll and Imd immune pathways confirmed the involvement of the Toll pathway in response to Nosema infection, and showed that there was a positive correlation between the Nosema spore load and levels of immune responses in infected bees. Our results provide clear evidence that N. ceranae infection can induce immune responses in infected bees under natural conditions, and provides a quantitative estimate of disease development as bees age. The information gained from this study will be relevant to the predictive modeling of honey bee disease dynamics for Nosema disease prevention and management.