The Veterinary Record, October 27, 2001
Sir, - Professor David King's article entitled "The use of vaccination in the current FMD outbreak", published on the DEFRA website and summarised in the Veterinary Record (September 29th, p370) has prompted us to respond, as there are a number of inaccuracies in his statements.
Contrary to Professor King's assertions that vaccination does not completely remove the virus, mass vaccination, as practised in continental Europe before1991, effectively eliminated foot and mouth disease (FMD) from the animal population (Salt 1997, Kitching 1998,). The most recent oil-based FMD vaccines are of high efficacy, and, with high levels of immunity any virus struggles to find a suitable host and eventually dies out (Anderson and May 1991).
Tests are now available to distinguish between vaccinated-immune and recovered-immune animals and also to identify animals that are harbouring the virus (Sorensen and others 1998). Non Structural Protein (NSP) ELISAS for antibodies to viral polyprotein 3ABC can distinguish between vaccinated animals and animals that have subsequently become infected with over 90 per cent sensitivity and specificity and have been validated on experimental and field sera in South America (Mackay 1998). A commercially available NSP test is intended to be available this autumn for cattle and pigs for use on a herd basis (Intervet website, www.intervet.com). This is the basis for 'vaccination to live'; a Dutch initiative which is currently being actively pursued in Europe.
The 'long tail' of this disease was not as predicted by Professor King. Indeed, in his statement of April 11th he referred to epidemiological models which indicated that the policy of 24 hour culling of infected premises and 48 hour culling of contiguous holdings would effectively deal with the outbreak by early June. Instead, from early May, a steady state was induced in which for four months, despite the most rigorous and extensive culling programme, there was no real decline in the number of outbreaks (in spite of the greatly reduced numbers of susceptible hosts) and so no true tail. This is in marked contrast to the 1967/68 epidemic, in which a short- lived disease tail preceded its disappearance.
Ring and suppressive vaccination as an adjunct to culling has been tried and tested in FMD outbreaks throughout the world (Salt 1997) and suppressive vaccination was used successfully in the recent Dutch outbreak. EU legislation currently requires the slaughter of animals vaccinated to control the disease, in order to regain disease-free status in the shortest possible time. If EU policy were to be changed following recommendations of the Scientific Committee on Emergency Vaccination in recognition of a post-vaccination surveillance system as discussed above, then FMD-free status could be rapidly regained by vaccinated herds/flocks without the need for culling. All arguments against vaccination would then disappear.
Finally, we cannot understand why the recommendations of the 1968 Committee of Inquiry into the 1967/68 FMD outbreak in the UK have been so shamefully ignored. Final recommendation number IV "We recommend that contingency plans for the application of ring vaccination should be kept in constant readiness"
Susan Haywood , Firs Farm, Keld, Richmond, N.Yorks. DL11 6LS
Sarah Binns, Staple Court House, Staple Cross, Hockworthy, Wellington, Somerset TA21 0NH
Sheila Crispin, Henley House, Swans Lane, Draycott, Cheddar, Somerset BS27 3SS
Paul Roger ,Victoria cottage, Reeth, Richmond, N. yorks. DL11 6SZ
Verner Wheelock, Binns Lane Farm, Binns Lane,Glusburn, Keighley, W.Yorks. BD20 8JJ
ANDERSON, R.M. and MAY, R.M. (1991) Infectious Diseases of Humans. Oxford, OUP, p.88.
KITCHING, P. (1998 ) A recent History of FMD. Journal of Comparative Pathology 118, 89-108
MACKAY, J. (1998) Differentiating infection from vaccination in foot-and-mouth disease. Proceedings of the Final Meeting of Concerted Action CT93 0909. Veterinary Quarterly 20 (Suppl 2), S1-S40.
SALT, J. (1997) Vaccination against FMD. Veterinary Vaccinology, Eds. PASTORET P.P., BLANCOU, J., VANNIER, P. and VERSCHUEREN, C., Amsterdam, Elsevier, pp 641-649
SORENSON, K.J., MADSEN, K.G., MADSEN, E.S., SALT, J.S., NQINDI, J., and MACKAY, D.J. (1998) Differentiation of infection from vaccination in foot and mouth disease by the detection of antibodies to the non-structural proteins 3D, 3AB and 3ABC in ELISA using antigens expressed in baculovirus. Archives of Virology, 148 (8), 1461 -76