Thank you for your reply Randy.
One can see the utility of qPCR in the study by Dolezal, et al (2016), “Honey Bee Viruses in Wild Bees: Viral Prevalence, Loads, and Experimental Inoculation.” PLOS ONE. November 10. However, for practical beekeeping purposes, the problem remains one of determining the threshold qPCR values at which point one can expect a clinical manifestation of disease, subject, possibly, to management intervention. Randy, you provide some threshold information re. DWV and paralytic viruses of which we appear to have neither at the moment.
Re. our testing of three samples of pooled bees from three apiaries in August 2017 by the Animal Health Laboratory (AHL) at the University of Guelph (Fn1), the AHL provided qPCR values for SBV and Nosema ceranae as well as DWV (we limited our testing to four pathogens ). All samples tested negative for EFB. I provided an example of a qPCR value for SBV previously. For Nosema ceranae, qPCR values ranged from “MDL copies/bee” (Fn2) to 2.21E+09 copies/bee to 6.87E+09 copies/bee.
I discussed the qPCR values re. Nosema ceranae with the provincial apiarist of Ontario. He is working with the AHL on the threshold issue. We all know that traditionally the threshold for treatment of Nosema, at least N. apis, has been based on a count of 1 million spores per bee (Fn3). The problem is that we often have clinical symptoms of nosema disease with spore counts well below 1 million, but on the other hand, no clinical symptoms with counts far above. For that reason the provincial apiarist and others in Ontario have been interested in developing qPCR approaches that would more accurately flag potential health problems in a colony, and trigger management solutions. As noted previously, we do not yet have the data to establish threshold values (or range of values?) for most if not all pathogens at which point one could expect symptoms. Re. the threshold data you provide, Randy, can I find that in the published literature?
Hopefully I haven’t garbled this summary.
Practically speaking, then, we have a qPCR value of 6.87E+09 copies/bee for Nosema ceranae without clinical manifestation. Should we be worried? Should the colonies with this qPCR value be treated? I haven’t got a clue.
Fn1. The three main labs that provide diagnostic services re. honey bees in Canada are the National Bee Diagnostic Centre in Beaverlodge, Alberta, the Animal Health Laboratory at the University of Guelph, and I believe the Centre de recherche en sciences animales de Deschambault in Quebec. I need to spend some time looking at what’s going on in Quebec, one of our other Canadian “solitudes”. The trouble with this solitude thing is that our Quebecois colleagues can be doing all kinds of interesting things often in parallel with Anglophone researchers but we pay little attention to them (or are tardy in so doing) because they publish in French.
At a glance I note the following of interest:
http://www.mapaq.gouv.qc.ca/SiteCollectionDocuments/Recherche_Innovation/Apiculture/807110.pdf
You can see some interesting qPCR related research in this study by Jabaji (2011), but no threshold qPCR values for clinical symptoms of N. ceranae are provided. Not a research purpose.
http://www.mapaq.gouv.qc.ca/SiteCollectionDocuments/Recherche_Innovation/Apiculture/807181.pdf
Fn2. MDL=”Sample has a crossing threshold (Cp) value of cycle 40 or greater. This sample is positive, but pathogen levels are too low for accurate quantification.”
Fn3. E.g., “When monitoring shows the N. apis intensity of infection has reached the economic threshold of 1 million spores per bee, treatment using chemical control should commence.” (S.F. Pernal and H. Clay [eds.]. 2013. Honey Bee Diseases and Pests. Beaverlodge, Alberta: Canadian Association of Professional Apiculturists. 3rd edition). Is this spore count methodology used with N. ceranae as well as N. apis?
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