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 DEFRA's argument for not including reference to the Smart Cycler RT-PCR technology in their most recent foot and mouth Contingency Plan would appear to be:

March 6 2004 ~ Row rumbles on over Brown's FMD diagnostic kit

    "Three years on from the world’s biggest foot-and-mouth outbreak, there is still no reliable rapid on-farm diagnostic test." writes Fordyce Maxwell in Saturday's Scotsman
      ".. Anne Lambourn, a Brown supporter and anti-slaughter as a way of controlling any future outbreak, told The Scotsman: "Defra seem entrenched in a medieval attitude to disease control and incapable of taking advantage of new technologies." .....Pirbright scientists take a different view of Brown’s claims that his Smart Cycler was "a beautiful piece of kit, simple and not costly". Three Pirbright scientists carried out an evaluation of the Cycler. Their findings in the Veterinary Record in summer 2002 were that it could not detect weakly positive samples and that further work was needed before it could be used for diagnosis in the field. .." Read Scotsman article in full
    The "three Pirbright scientists'" findings in the Veterinary Record were only partially reported by DEFRA (see below)
    For DEFRA to imply that the paper by Hearps, Zhang and Alexandersen in 2002 gives them a good reason not to include any mention of the technology in the Contingency plan rather takes one's breath away. "
In June 2003, the Institute of Animal Health’s Report on the Science of Vaccination was published and this provided an update with regard to rapid diagnostic tests. You can view this report at http://www.defra.gov.uk/footandmouth/pdf/fmdreview.pdf

The “Smart Cycler” was evaluated by Hearps, Zhang and Alexandersen in 2002 and was found unable to detect weakly positive samples.
Further work is required before such tests could be used for diagnosis in the field as a matter of course.
Defra is continuing to fund research into RT-PCR tests including development and validation of automated, high throughput testing.

It is interesting to hear that or DEFRA "is continuing to fund research into RT-PCR tests including development and validation of automated, high throughput testing." Further details would be helpful. But for DEFRA to imply that the paper by  Hearps, Zhang and Alexandersen in 2002 gives them a good reason not to include any mention of the technology in the Contingency plan takes one's breath away. 

DEFRA is perhaps not aware that when Hearps, A., Zhang, Z., and Alexandersen, S. wrote that article  in the Vet Record they clearly accepted that   ".. the ability of the machine to detect viral RNA is greatly affected by the PCR reagents used for the assay. When it was used with PCR beads it was unable to detect weakly positive samples, but when TaqMan core reagents were used for the assay, its sensitivity was significantly increased."

 Roger Breeze's tactful letter  back in 2001  to the Royal Society Inquiry  http://www.royalsoc.ac.uk/inquiry/388.pdf   referred to the Vet Record article and its use of "reagents". 

I have no idea what those reagents were because the paper does not describe them. But I can be sure that these reagents were not those developed by USDA-ARS and Tetracore because Cepheid does not have this proprietary information.

I hope there has been no confusion in Britain between the Cepheid mystery test and the real time PCR test developed at Plum Island.

I did consider writing to the Veterinary Record at the time to clarify this but decided this was not worthwhile since Donaldson's letter was largely anecdotal and Cepheid clearly had no capability in FMD detection, so it was hard to believe anyone would take his comments seriously

.....Much reference continues to be made to the relative sensitivities of cell culture and RT-PCR and to the need for spurious comparisons with lab-based PCR instruments

In our assay, RT-PCR is more sensitive than cell culture. When it is possible to do cell culture on the farm - or use fragile lab-based PCR devices in vehicles - we can have a direct head to head challenge of technologies, but until then, the ARS RT-PCR for FMD is the new standard for on-site diagnosis of FMD. We are pursuing the appropriate licensing of this test by US regulatory authorities and approval by OIE.

 

 The fact that 80% of US State Laboratories  (according to a Cepheid installer quoted in warmwell on Feb 20)  now use the Smart Cycler should perhaps give  DEFRA   pause for thought.   It is interesting that , although DEFRA is keen to mention ( out of context) the phrase "unable to detect weakly positive samples" no mention is made of another abstract, also quoted in the FMDreview ( http://www.defra.gov.uk/footandmouth/pdf/fmdreview.pdf )

 

Callahan JD, Brown F, Osorio FA, Sur JH, Kramer E, Long GW, Lubroth J, Ellis SJ, Shoulars KS, Gaffney KL, Rock DL, Nelson WM. 2002. Use of a portable real-time reverse transcriptase-polymerase chain reaction assay for rapid detection of foot-and-mouth disease virus. J Am Vet Med Assoc. 220(11):1636-42. Abstract: OBJECTIVE: To evaluate a portable real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay designed to detect all 7 viral serotypes of foot-and-mouth disease virus (FMDV). DESIGN: Laboratory and animal studies. STUDY POPULATION: Viruses grown in tissue culture and animals experimentally infected with FMDV. PROCEDURE: 1 steer, pig, and sheep were infected with serotype O FMDV. Twenty-four hours later, animals were placed in separate rooms that contained 4 FMDV-free, healthy animals of the same species. Oral and nasal swab specimens, oropharyngeal specimens obtained with a probang, and blood samples were obtained at frequent intervals, and animals were observed for fever and clinical signs of foot-a nd-mouth disease (FMD). Samples from animals and tissue cultures were assayed for infectious virus and viral RNA. RESULTS: The assay detected viral RNA representing all 7 FMDV serotypes grown in tissue culture but did not amplify a panel of selected viruses that included those that cause vesicular diseases similar to FMD; thus, the assay had a specificity of 100%, depending on the panel selected. The assay also met or exceeded sensitivity

 

 

 

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