Email received August 10th 2011
Regarding today's article on your site, I have recently been looking at the prevalence of TB in badgers and cattle, and I have recorded what I found at .
I found Ref 8 on the above page interesting because I think it implies that half the infected cage-trapped badgers, which showed symptoms in a more thorough examination, had been missed in results of examinations reported in the RBCT report.
As you probably already know the full Krebs report at
looks at the prevalence in badgers from various road kill pre 1997. It also compares the prevalence in badgers measured in the live trial and the interim strategy. Such prevalences came out at 37.5% and 34.1% respectively.
The following is an extract taken from work reported by J.Gallagher and R.S. Clifton-Hadley.
Nolan (1991) identified an immuno-dominant component of M.bovis which was present in all isolates examined and absent from other mycobacteria. Using this she developed a blocking ELISA. This was later developed into an indirect ELISA using the highly specific 25 kDa antigen (Goodger et al., 1994). Field trials of this test showed a very high specificity of 94.3% but its sensitivity was low at 40.7%. However, the sensitivity was significantly higher, 62.3%, in animals found to have gross lesions.
Hence even if the ELISA test is performed on badgers which all have gross lesions, typically just over a third of these badgers will not be picked up by the ELISA test. I understand that this is a measure of the performance of the test developed in 1994. I do not know if there have been significant advances since then.
Badgers sanctuaries use the ELISA test prior to releasing badgers cubs back into the wild. According to their voluntary protocol they test the cubs three times over a sufficiently long time scale to improve the detection rate. The link below shows a copy of this protocol.