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Foot-and-mouth infectious for less time - raising hopes for binning culls

By Martin Leggett - 05 May 2011 18:0:0 GMT

The shocking slaughter and waste of a 'cull-first think-later' policy, for dealing with foot-and-mouth - see on an unprecedented scale in the UK's 2001 livestock outbreakf - has been driven home by powerful new research published in tomorrow's Science. It shows that the foot-and-mouth disease virus (FMDV) is infectious for a much shorter period than previously assumed - raising serious doubts over policies of mass culling.

The finding also opens the door to much less onerous strategies for dealing with new outbreaks. A quick-footed isolation strategy for infected cattle could be a likely way to stop a FMDV infection in its tracks. But this research goes much further - raising the prospect of changing the way health practitioners deal with a number of viral infections, including human flu-pandemics.

FMDV is an unpleasant, but rarely fatal, infection for cattle, sheep and other livestock. Most animals get well in a few days - but they can suffer from weight loss and lameness after recovery. But for farmers, its rapid spread can render the livestock of a whole farm economically valueless -  so many countries, including the UK, opt for a severe culling policy, at the first sign of symptoms.

But that controversial and heart-rending destruction is based on an assumption that the virus can be spread even when there are no actual symptoms present. In this ground-breaking research, scientists from the UK's Pirbright Laboratory tracked infected cows, in close proximity with healthy animals, to see exactly how symptoms and infectiousness were linked. What they found was that the disease's spread was limited to a 1.7 day slot, half a day after the symptoms first became obvious. That is a much smaller time-frame than previously assumed.

Co-author of the study, Mark Woolhouse from the University of Edinburgh, said ''We now know that there is a window where, if affected cattle are detected and removed from the herd promptly, there may be no need for preemptive culling in the immediate area of an infected farm.'' Given that the 2001 UK outbreak led to the slaughter of 10 million sheep and cattle, this has major implications for farm animal welfare, as well as farmers livelihoods.

It may also be necessary to look more closely at strategies for dealing with other diseases. Models for those may also be based on incorrect assumptions about the length of time animals - or people - are infectious. ''We urgently need to evaluate other infections,'' said Woolhouse.

The study also highlights the importance of weighing government policies with proper scientific evidence, rather than skimping on research, in a false drive to cut costs. Woolhouse said ''People have used short-cuts before and we can end up with misleading information. This new research tells me that we can't afford to take those short-cuts. This is the kind of work we need to be doing to learn how to manage infectious diseases in the future.''