The effects of Nosema ceranae infection on honey bee health and Colony Collapse Disorder

The effects of Nosema ceranae infection on honey bee health and Colony Collapse Disorder

Summary

The objective of this research is to investigate the effects of Nosema ceranae infection on the behavioral development and physiology of honey bees (Apis mellifera). This disease is one of the factors implicated in the recent annual collapse of colonies in beekeeping operations throughout the U.S. The regulatory interaction between the yolk precursor protein, vitellogenin (Vg), and juvenile hormone (JH) is fundamental to the behavioral development of honey bees. N. ceranae is an obligate intracellular fungus that infects the midgut of adult bees. N. ceranae infection may disrupt Vg/JH endocrine signaling, leading to pathological and premature onset of foraging and a shortened life span. Results from this novel research will provide a foundation for future studies aiming to understand the pathological effects of N. ceranae in A. mellifera colonies, and will ultimately help North Central Region and U.S. beekeepers’ develop management techniques and sustainable means to control this emerging pathogen.

Objectives/Performance Targets

Objective 1. Determine how N. ceranae infection affects expression of Vg and JH in honey bees.
Objective 2. Determine the life span and identify the onset of foraging behavior in newly emerged worker bees infected with N. ceranae.

Accomplishments/Milestones

Objective 1. We compared honey bees infected with Nosema ceranae with uninfected bees. Bees were evaluated for spore load, levels of Vg and JH at 4, 8, 12, and 16 days after infection. Spore load in Nosema-infected bees increased to approximately 25 million spores/bee at 16 days after infection. Vg levels in uninfected bees showed a pattern typical of normal development with a steady increase that peaked at 8 days. Vg levels in Nosema-infected bees showed a distinctly different pattern where expression remained low through day 12. This finding supports our hypothesis that Nosema ceranae infection may be disrupting Vg/JH endocrine signaling. We are currently undergoing analysis of JH levels by radioimmunoassay and compare its profile to Vg levels.

Objective 2. We compared the onset of foraging behavior in honey bees infected with Nosema ceranae with uninfected bees. Bees were paint-marked by infection status and introduced into small colonies. Colonies were observed daily during starting at 5 days until 21 days after infection and returning marked foragers were collected for spore load and Vg/JH analysis. Findings from show that there were nearly twice as many bees from the Nosema-infected bees collected during foraging observations compared to uninfected controls. We are currently undergoing analysis of JH titer and Vg expression in collected bees.

Impacts and Contributions/Outcomes

The immediate goal of this research is to establish a correlation between the yolk precursor protein, vitellogenin (Vg), juvenile hormone (JH), and foraging onset and life span in honey bees infected with Nosema ceranae. This research will help beekeepers and researchers understand how this disease affects honey bee colonies. For the intermediate-term, this research will help develop new control strategies for this disease, including breeding honey bees for resistance to Nosema.

Ultimately, this research seeks to promote the health of honey bees, which directly benefits farmers in the NCR who produce fruits and vegetables or grow wildflowers for sale as seed or ornamentals.

Another long-term goal is to promote the vitality of the beekeeping industry in the NCR, which benefits beekeepers nationwide. Most commercial beekeeping operations in the NCR are migratory, meaning they transport their colonies from the NCR to other states for pollination services. In addition, many beekeepers in the NCR maintain “nursery stocks” to sell to other beekeepers. Therefore, promoting sustainable beekeeping in the NCR will enhance the quality of life for farmers, beekeepers, and society as a whole.