Science - November 3, 2011

Messy procedure adds to unease about foot & mouth outbreak

The CVI in Lelystad bungled things a bit during the Foot & Mouth crisis in the village of Kootwijkerbroek, new research suggests.

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The discovery of foot & mouth disease in Kootwijkerbroek led to the culling of 60,000 animals. The affected farmers have already been contesting that decision for ten years. Now state secretary Bleker has had experts investigate how the Central Veterinary Institute (CVI) came to the conclusion at the end of March 2001 that foot & mouth disease had broken out.
In their study, two foreign foot & mouth experts scrutinize the laboratory tests and procedures used at the time. With interesting results. To prove the presence of foot & mouth, two positive tests are required: both the virus itself and the antigen to it should be identified. After a long (and messy: see box) run-up, both tests turned out positive on 28 March 2001. This was reported to the ministry by fax. Culling started the same day.
But a second test four days later (on 1 April), using the same sample, turned out differently. The test on the antigen now gave a negative result. This was never reported. According to the CVI, staff thought that two samples had been ‘accidentally' interchanged. But the experts are not convinced of this. They think the negative test result was ‘probably valid', but no further tests were carried out because the researchers doubted the accuracy of the test.

Negligent
‘Lamentable', is how C. Westeneng, chair of the foundation for the foot & mouth research in Kootwijkerbroek, describes the revelations in the experts' report. ‘Ten years later it turns out that the second test was negative. Something else comes to light all the time.' But from a legal angle, this revelation is not relevant, according to Westeneng. ‘What counts is what happened on 28 March. That is when the decision was made that there was foot & mouth disease. But this does put the issue in a different light of course. Whether the experts' conclusion is right, it is too soon for me to say. But our doubts have only grown since 2001.'
As it happens, the contested fax to the ministry does not even mention the positive antigen test of 28 March. It should have done so, say the experts. Without the antigen test, the evidence of foot & mouth is not conclusive. The experts see two possibilities: either the CVI was ‘negligent' or the fax with the conclusion was sent before the result of the antigen test was known. In either case, the identification of an outbreak of foot & mouth was not valid.
But the experts do not go this far. They believe the ministry's written statement that it had always viewed the two tests as one whole. Moreover, they say, tests on other samples after 28 March justify the decision to declare an outbreak of foot & mouth ‘with hindsight'. The CVI has issued a written statement saying it is ‘pleased' with the conclusions of the experts. According to director A. Bianchi, the study confirms that foot & mouth was rightly identified at the time. The fact that procedures were not always followed was due to the need for haste, he says.

Messy research
The experts' study gives us a peek behind the scenes at CVI in 2001. To demonstrate the presence of the virus, the samples were initially grafted on to cell cultures from pig's kidney. But the virus did not grow well on this, so a switch was made to lamb's kidney cells, which the CVI had in stock. What they did not have was enough glass test tubes. A switch to plastic test tubes failed: the lamb's kidney cells did not stick well to the plastic. So it was decided to purchase fresh material: a lamb from a foot & mouth-free part of the country. This animal's kidney cells did prove suited to plastic test tubes - although nobody checked whether the lamb really was free of the virus.
At last, on 27 March 2001, a week after the arrival of the first samples, the operation succeeded. Result: foot & mouth. In their report, the experts describe this sequence of events as ‘telling information.'
 

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