Thursday, June 14, 2012

We like this...

Searching for something else can sometimes turn up solid gold. And a search today has done just that.
PCR (Polymerase Chain Reaction) has been around for decades now, and  the most logical use of it with bTB would be to identify infected badger setts as opposed to those used by groups relatively clean and healthy. Ex WLU staff tell us that much of the resistance to culling badgers across wide areas using mathematical models could be negated if more confidence could be given to the disease status of the badgers themselves.

So it is with our apologies that we have to say, we missed this one, submitted for publication in August 2011, and published November 14th 2011 as a validated, peer reviewed piece in PlosOne. It is attributed to Travis E.R et al (2011) and entitled;

"An inter-laboratory validation of a real time PCR assay to measure host excretion of bacterial pathogens, particularly of mycobacterium bovis".

The Abstract from the paper :
Advances in the diagnosis of Mycobacterium bovis infection in wildlife hosts may benefit the development of sustainable approaches to the management of bovine tuberculosis in cattle. In the present study, three laboratories from two different countries participated in a validation trial to evaluate the reliability and reproducibility of a real time PCR assay in the detection and quantification of M. bovis from environmental samples.
The sample panels consisted of negative badger faeces spiked with a dilution series of M. bovis BCG Pasteur and of field samples of faeces from badgers of unknown infection status taken from badger latrines in areas with high and low incidence of bovine TB (bTB) in cattle. Samples were tested with a previously optimised methodology. The experimental design involved rigorous testing which highlighted a number of potential pitfalls in the analysis of environmental samples using real time PCR. Despite minor variation between operators and laboratories, the validation study demonstrated good concordance between the three laboratories: on the spiked panels, the test showed high levels of agreement in terms of positive/negative detection, with high specificity (100%)and high sensitivity (97%) at levels of 105 cells g21 and above.
Quantitative analysis of the data revealed low variability in recovery of BCG cells between laboratories and operators. On the field samples, the test showed high reproducibility both in terms of positive/negative detection and in the number of cells detected, despite low numbers of samples identified as positive by any laboratory. Use of a parallel PCR inhibition control assay revealed negligible PCR-interfering chemicals coextracted with the DNA.
This is the first example of a multi-laboratory validation of a real time PCR assay for the detection of mycobacteria in environmental samples. Field studies are now required to determine how best to apply the assay for population-level bTB surveillance in wildlife.
So, what are we waiting for? The field trial could be done at Badger Heaven  Woodchester Park, where not only is the disease status of every social group known and has been logged for decades, but no doubt individual badgers have Christian names too. This is from where some of  the 300 field samples mentioned in this study were matched to epidemiological information already held. Will someone please contact Brian May, the RSPCA, Jack Reedy and Secret World. In no particular order of course, but perhaps include Jim Paice too - as his department co-funded this project, he may be interested. Or not.

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