Temporal study of Nosema spp. in a cold climate

Area of Science:

• Apiculture
• Microbiology
• Veterinary Entomology

Background:

• Nosema species are microsporidian parasites affecting honey bee health.
• Nosema ceranae has emerged globally, raising concerns about its impact on honey bee populations.
• Understanding the prevalence and dynamics of Nosema infections is crucial for apiculture management.

Purpose of the Study:

• To assess the prevalence and dynamics of Nosema apis and Nosema ceranae infections in Swedish honey bee colonies.
• To determine if Nosema ceranae is increasing and potentially replacing Nosema apis in Sweden.
• To provide data for informed beekeeping practices and disease management strategies.

Main Methods:

• Nationwide survey of 967 honey bee colonies across Sweden in 2007.
• Molecular analysis (DNA proportion) to identify and quantify Nosema species.
• Follow-up sampling of previously identified Nosema ceranae positive colonies in 2009 and 2011.

Main Results:

• Nosema apis was the dominant infection, found in 284 out of 319 positive samples.
• Only one pure Nosema ceranae infection was detected; mixed infections were rare.
• No significant increase in Nosema ceranae prevalence or proportion in mixed infections was observed between 2007 and 2011.

Conclusions:

• Nosema apis remains the primary microsporidian pathogen affecting honey bees in Sweden.
• Current data does not support a trend of Nosema ceranae displacing Nosema apis in the Swedish honey bee population.
• Continued monitoring is recommended to track potential shifts in Nosema species dynamics.