From The Australian, 9 March 2002 BETTER FOOT & MOUTH TEST WILL BOOST DEFENSE
By Sophie Morris
"John Crowther from the Animal Production and Health Division of the
Vienna-based IAEA said the three commercial test kits now available were limited in their usefulness because they did not differentiate between vaccinated and infected animals.....The three serum tests could not distinguish between the antibody contained in the vaccine and the antibody produced by the virus.
"If there is an outbreak you are going to want to screen for the disease, and if Australia did decide to vaccinate, it is important to have a test to show that after vaccination the cattle are disease free," Dr Crowther said.
He said the scientists, from 15 countries, would set criteria for a test that could be used around the world to establish a country's status as free from FMD. This would also help countries recovering after an outbreak to prove their exports were clean.
"We are wanting to develop a test which would allow you to do lots of samples fairly quickly and cheaply," he said. ."
.............................Alicia Eykyn writes:
I wrote to John Crowther and asked him if this was truly his position or whether in the light of what he said both to us personally and on the platform at the Lyons Symposium he was being mis-quoted. This is, in summary, his reply:
'I hope the following is helpful. Please feel free to use data on anyone who bullshits. I know that people want a perfect test that unequivocally decides that an animal is absolutely free from any contact with FMD.The very nature of the agent means that this is impossible.However, we can, using the assays for NS move towards ensuring that the risk of spreading disease is greatly reduced, which in turn may lead to a re interpretation of acceptable risks for the "release" of serologically free animals which hitherto would be slaughtered.Is that vague enough to be mis interpreted by anyone (Yes). One great use of all the assays (meaning NS
antibody tests) is to re-write the epidemiology of FMD with respect to detecting areas where, in the face of vaccination, we have replication events".
A few points.
1. In principle and practice , all the commercially oriented assays measure antibodies against the NS proteins of FMD, therefore all can discriminate between vaccinated and infected livestock. All tests insist that the basis of testing is at the herd level where the prevalence of anti NS antibodies is assessed in a number of animals to indicate infection.
2. There are differences in the extent of validation of all the assays in terms of what sera have been looked at, which labs have looked at tests(world wide) how many sera have been assessed. The purpose of my involvement is to extend the process of validation and increase the validation to allow a better estimate of the actual usefulness of all the assays.
3. All the assays UBI, Bommeli, PANAFTOSA and all the research based reagent sets measuring NS antibodies, have similar sensitivities, but there are differences according to diagnostic performance. Some are better for measuring pig antibodies, some better at bovine etc. The exact systems used(antigen used, conjugates used) affect the ability of the tests to measure the large spectrum of antibodies produced in all species at various times after infection. Again this is to be examined in my exercises, merely to measure the exact performance so that tests might be assessed appropriately exploited by end users.
4. UBI have been with my CRP (coordinated Research Programme) from the beginning in spirit as well as practically, giving kits in the first exercises. They are now responding to the needs of the users in terms of including secondary intermediate controls, re tuning the sensitivities etc,in fact are fully committed (at cost) to producing worthwhile kits in as complete a package and at the lowest cost possible. The company I believe is important in ensuring that kits in fact will be available at all in the future, despite the fact that veterinary kits are notoriously non profit entities. I would add that I have appreciated the commercial input from all forms but it is a very difficult area rationalising what people conceive as profit against national use. We must sort this out, since commercial expertise at distribution is the main criterion for sustainable possibilities in kit supply.
5. The new tests being referred to with developments in Vienna and Australia are to be competitive ELISAs. This is because the present tests are Indirect ELISAs and may have greater problems picking up all antibodies from all species in the world. This maybe the reason for the sound bite reference to me saying that the present tests were generally no good. It remains to be seen whether we can provide masses of reagents which show superior properties to the present tests However, such reagents will have to be commercialised anyway to allow their sustainable distribution.
6. The new ruling by the OIE that such NS tests have to be used with others to verify FMD disease freedom rather pre-empts validation exercises needed.