IF FOOT and mouth disease does spread to continental Europe, the chances are
that animals will have caught it from imported livestock, not from virus-laden
wind blowing in from Britain.
Researchers are reasonably confident that the clouds of virus have been too
dilute to spread the disease to mainland Europe. 鈥淲e could not totally exclude
the risk of airborne spread to Europe, but it鈥檚 very very low,鈥� says Alex
Donaldson, head of the Institute for Animal Health in Surrey.
Together with teams at Britain鈥檚 Meteorological Office in Berkshire and at
the Danish Meteorological Institute in Copenhagen, the Institute for Animal
Health has adapted models for plotting nuclear fallout to predict the spread of
foot and mouth. The researchers have spent decades refining this modelling
system, called VPM-Rimpuff.
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They are currently concentrating on the outbreaks at pig farms, which
generate the most airborne virus. 鈥淧igs release anything from 40 million to 400
million infectious virus units per day,鈥� says Donaldson. 鈥淚t only takes 10
viruses to infect a cow.鈥�
The key factors affecting spread include temperature and relative humidity.
Cold, damp winter conditions favour the virus. To find out where it could get
to, the meteorologists are focusing on wind plumes from the three British pig
farms, in Northumberland and Essex, which have had outbreaks.
鈥淭here was plume dispersion south from Northumberland and also eastwards
towards Denmark, Holland and Belgium,鈥� says Donaldson. Preliminary analyses
suggest the plumes from the Essex pig farms were initially highly concentrated,
but dissipated as they drifted out over the North Sea. 鈥淲e think the
concentration was below the threshold to infect cattle [in Europe],鈥� says
Donaldson.
Other British pig farms might also be infected, Donaldson says, but the
researchers are hoping the three pig outbreaks will prove to be the only ones.
This would allow the investigators concentrate on detecting and managing the
cases spread by movement of animals.