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On-site DNA Detection of Trypanosomatid Parasites and Nosema ceranae Through Alkaline Lysis Coupled to RPA/CRISPR/Cas12a System
Published on: July 18, 2025
Individual Variability of Nosema ceranae Infections in Apis mellifera Colonies
Grace E Mulholland1, Brenna E Traver2, Nels G Johnson3
1Department of Entomology, Virginia Tech, 324 Price Hall, Blacksburg, VA 24061, USA. gracem@vt.edu.
Abstract:
Since 2006, beekeepers have reported increased losses of Apis mellifera colonies, and one factor that has been potentially implicated in these losses is the microsporidian Nosema ceranae. Since N. ceranae is a fairly recently discovered parasite, there is little knowledge of the variation in infection levels among individual workers within a colony. In this study we examined the levels of infection in individual bees from five colonies over three seasons using both spore counting and quantitative real-time PCR. The results show considerable intra-colony variation in infection intensity among individual workers with a higher percentage of low-level infections detected by PCR than by spore counting. Colonies generally had the highest percentage of infected bees in early summer (June) and the lowest levels in the fall (September). Nosema apis was detected in only 16/705 bees (2.3%) and always as a low-level co-infection with N. ceranae. The results also indicate that intra-colony variation in infection levels could influence the accuracy of Nosema diagnosis.
Insights
Individual honey bee (Apis mellifera) colonies show significant variation in Nosema ceranae parasite levels. This variation, especially low-level Nosema infections, impacts disease diagnosis accuracy and colony health management.
Area of Science:
- Veterinary Entomology
- Apiculture Science
- Microbial Ecology
Background:
- Honey bee colony losses have increased since 2006.
- The microsporidian Nosema ceranae is a suspected factor in these losses.
- Limited understanding exists regarding Nosema ceranae infection variability within individual honey bee colonies.
Purpose of the Study:
- To investigate the variation in Nosema ceranae infection levels among individual Apis mellifera workers.
- To compare infection detection methods (spore counting vs. quantitative PCR).
- To analyze seasonal trends in Nosema infection intensity within colonies.
Main Methods:
- Examined infection levels in individual bees from five colonies over three seasons.
- Utilized both traditional spore counting and quantitative real-time PCR for detection.
- Assessed the prevalence and intensity of Nosema ceranae and Nosema apis infections.
Main Results:
- Demonstrated considerable intra-colony variation in Nosema ceranae infection intensity.
- Quantitative PCR detected a higher percentage of low-level infections compared to spore counting.
- Infection prevalence peaked in early summer (June) and was lowest in fall (September).
- Nosema apis co-infections were rare (2.3%) and low-level.
Conclusions:
- Intra-colony variation in Nosema infection levels significantly affects diagnostic accuracy.
- Understanding this variation is crucial for effective Apis mellifera colony management and health monitoring.
- Quantitative PCR offers improved sensitivity for detecting low-level Nosema infections.
