An inter-laboratory comparison of molecular methods for the identification of Nosema species in honeybee samples
To evaluate the performance of the molecular methods used by national reference laboratories (NRLs) for the identification of Nosema species in bee samples, an inter-laboratory comparison (ILC) was organised in 2015. A total of 20 EU NRLs and 1 non-European NRL participated in this ILC. The specificity of the methods was tested on various Nosema species: Nosema apis, Nosema ceranae and Nosema bombi. The test panel of samples provided to the laboratories contained 17 suspensions of crushed abdomens from naturally and artificially infected honeybees and bumblebees. In addition, data on the routine methods used by the participating laboratories were collected in an online survey, covering all the steps involved in DNA extraction and PCR. Our analysis showed that the 21 NRLs use 21 different protocols, each presenting variations from the DNA extraction step to the PCR step. The results of this ILC indicate that 48% of the participating laboratories returned the expected results. Considering the 21 different methods used, 57% of participating laboratories provided satisfactory results with regard to sensitivity, and 72% with regard to specificity. The results of this ILC clearly highlight the need for improved harmonisation of molecular Nosema identification methods.