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The Western honey bee Apis mellifera, which provides about 90% of commercial pollination, is under threat from diverse abiotic and biotic factors. The ectoparasitic mite Varroa destructor vectoring deformed wing virus (DWV) has been identified as the main biotic contributor to honey bee colony losses worldwide, while the role of the microsporidium Nosema ceranae is still controversially discussed. In an attempt to solve this controversy, we statistically analyzed a unique data set on honey bee colony health collected from a cohort of honey bee colonies over 15 years and comprising more than 3000 data sets on mite infestation levels, Nosema spp. infections, and winter losses. Multivariate statistical analysis confirms that V. destructor is the major cause of colony winter losses. Although N. ceranae infections are also statistically significantly correlated with colony losses, determination of the effect size reveals that N. ceranae infections are of no or low biological relevance.The analysis of a dataset collected over 15 years reveals no biological relevance of Nosema ceranae infections for colony losses; hence, N. ceranae is not considered a serious threat for honey bees in the background of Varroa destructor infestations. [ABSTRACT FROM AUTHOR]

Nosema ceranae is a ubiquitous microsporidian pathogen infecting the midgut of honey bees. The infection causes bee nosemosis, a disease associated with malnutrition, dysentery, and lethargic behavior, and results in considerable economic losses in apiculture. The use of a rapid, sensitive, and inexpensive DNA-based molecular detection method assists in the surveillance and eventual control of this pathogen. To this end, a loop-mediated isothermal amplification (LAMP) assay targeting the single-copy gene encoding the polar tube protein 3 (PTP3) has been developed. Genomic DNA of N. ceranae–infected forager bees sampled from distant geographic regions could be reliably amplified using the established LAMP assay. The N. ceranae-LAMP showed higher sensitivity than a classical reference PCR (98.6 vs 95.7%), when both approaches were applied to the detection of N. ceranae. LAMP detected a ten-fold lower infection rate than the reference PCR (1 pg vs 10 pg genomic DNA, respectively). In addition, we show highly specific and sensitive detection of N. ceranae from spore preparations in a direct LAMP format. No cross-reactions with genomic DNA and/or spores from N. apis, often co-infecting A. mellifera, or from N. bombi, infecting bumble bees, were observed. This low-cost and time-saving molecular detection method can be easily applied in simple laboratory settings, facilitating a rapid detection of N. ceranae in honey bees in epidemiological studies, surveillance and control, as well as evaluation of therapeutic measures against nosemosis. [ABSTRACT FROM AUTHOR]