The Animal Health Laboratory (AHL) at the University of Guelph offers quantitative PCR (qPCR) as part of its testing services. See https://www.uoguelph.ca/ahl/ahl-labnote-32-honey-bee-testing-ahl  I had a small sample of bees tested last August for EFB, DWV, Nosema ceranae, and SBV.  I would have included other pathogens in the testing, but it’s expensive.

The qPCR test results look this (using SBV as an example):

Specimen type – Bee pool
Result (Ct) – 34.69
Interpretation – POSITIVE
Quantification – 1.11E+05 copies/bee
Comments: Ct (threshold cycle) is the intersection between an amplification curve and a threshold line. It is a relative measure of the concentration of target in the PCR reaction.  A lower Ct value indicates a higher concentration of the target RNA/DNA in the sample.

What is a beekeeper supposed to do with test result data like this? Yep, the sample is positive for SBV.  But what does the quantification figure mean?  I have never seen clinical symptoms of SBV in my colonies.

What I learned in my discussions with the AHL and the provincial apiarist in Ontario is that they have not yet been able to associate qPCR values with clinical manifestations of disease.  They cannot say that you are likely to see SBV in a colony when a specific qPCR threshold (i.e., number of copies/bee) is reached. This begs the question re. the value of offering qPCR testing to beekeepers.  

The fact that qPCR appears to be very much a technology/methodology in development was recognized by the National Bee Diagnostic Centre in its 2016 report re. the Canadian National Honey Bee Health Survey. One of the testing limitations identified relates to qPCR: 

“ The use of PCR is an effective diagnostic technique, but is also very sensitive. Therefore, a positive detection using the technique does not conclusively diagnose an active or overt condition.  Specifically, PCR detection of EFB and the viral panel require further development, such as quantitative PCR, to more accurately associate positive detections with possible clinical symptoms in an apiary.” 

Do any of you know of any efforts to associate qPCR data with thresholds for clinical manifestations of honey bee diseases?  Any results from such efforts?

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