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. 2012 Nov 1;3(4):1143-55.
doi: 10.3390/insects3041143.

Individual Variability of Nosema Ceranae Infections in Apis Mellifera Colonies

Free PMC article

Individual Variability of Nosema Ceranae Infections in Apis Mellifera Colonies

Grace E Mulholland et al. Insects. .
Free PMC article


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.

Keywords: Apis mellifera; Nosema apis; Nosema ceranae; real-time PCR; spore count; variability.


Figure 1
Figure 1
Variation in the mean number of N. ceranae DNA copies (in a standardized 50 ng sample/bee) and spore counts for the same individual bees. The line represents a cut-off point, 10 copies, at which we can reliably detect N. ceranae levels. Black bars represent the mean N. ceranae DNA copies from each bee sample while the gray bars represent the mean spore counts for the same bee. (a) Data from colony 3 in the spring (b) Data from colony 1 in the summer (c) Data from colony 3 in the fall.

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