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Updated: May 10, 2026
Preparation of Virus-Enriched Inoculum for Oral Infection of Honey Bees Apis mellifera
Published on: August 26, 2020
Exploring the interactions between Nosema ceranae infection and the honey bee gut microbiome
Edmund Lau1, Jessica Maccaro2, Quinn S McFrederick3
1School of Biological Sciences, Department of Ecology, Behavior, and Evolution, University of California San Diego, La Jolla, CA, 92093, USA.
Abstract:
Managed colonies of the European honey bee, Apis mellifera, have faced considerable losses in recent years. A widespread contributing factor is a microsporidian pathogen, Nosema ceranae, which occurs worldwide, is increasingly resistant to antibiotic treatment, and can alter the host's immune response and nutritional uptake. These obligate gut pathogens share their environment with a natural honey bee microbiome whose composition can affect pathogen resistance. We tested the effect of N. ceranae infection on this microbiome by feeding 5 day-old adult bees that had natural, fully developed microbiomes with live N. ceranae spores (40,000 per bee) or a sham inoculation, sterile 2.0 M sucrose solution. We caged and reared these bees in a controlled lab environment and tracked their mortality over 12 d, after which we dissected them, measured their infection levels (gut spore counts), and analyzed their microbiomes. Bees fed live spores had two-fold higher mortality by 12 d and 36.5-fold more spores per bee than controls. There were also strong colony effects on infection levels, and 9% of spore-inoculated bees had no spore counts at all (defined as fed-spores-but-not-infected). Nosema ceranae infection had significant but subtle effects on the gut microbiomes of experimentally infected bees, bees with different infection levels, and fed-spores-but-not-infected vs. bees with gut spores. Specific bacteria, including Gilliamella ASVs, were positively associated with infection, indicating that multiple strains of core gut microbes either facilitate or resist N. ceranae infection. Future studies on the interactions between bacterial, pathogen, and host genotypes would be illuminating.
Insights
European honey bee (Apis mellifera) losses are linked to Nosema ceranae infection. This pathogen alters the bee microbiome, impacting resistance. Specific gut bacteria may influence infection severity.
Area of Science:
- Apiculture
- Insect Pathology
- Microbiome Research
Background:
- Managed honey bee colonies face significant losses, with Nosema ceranae identified as a major contributing factor.
- Nosema ceranae is a global microsporidian pathogen resistant to antibiotics, affecting bee immunity and nutrition.
- The honey bee gut microbiome plays a crucial role in pathogen resistance.
Purpose of the Study:
- To investigate the impact of Nosema ceranae infection on the honey bee gut microbiome.
- To understand how N. ceranae infection influences bee mortality and pathogen load.
- To identify specific microbial associations with N. ceranae infection.
Main Methods:
- Adult European honey bees (Apis mellifera) with established microbiomes were experimentally infected with N. ceranae spores.
- Control groups received sham inoculations.
- Mortality was tracked over 12 days, followed by dissection to measure gut spore counts and analyze microbiome composition.
Main Results:
- Bees infected with N. ceranae exhibited a two-fold increase in mortality and a 36.5-fold higher spore count compared to controls.
- N. ceranae infection caused significant, though subtle, alterations in the gut microbiome.
- Specific bacteria, such as Gilliamella ASVs, were positively associated with N. ceranae infection levels.
Conclusions:
- Nosema ceranae infection significantly impacts honey bee mortality and gut microbiome composition.
- The composition of the honey bee gut microbiome can influence N. ceranae infection dynamics.
- Interactions between specific gut bacteria, the pathogen, and host genetics warrant further investigation for bee health management.
