Atlas tracks foot and mouth

NEW ZEALAND - Scientists have mapped out the likely course that foot-and-mouth disease would take if an outbreak were to occur in Canterbury. T. Cronshaw reports.
calendar icon 10 November 2006
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An atlas by the National Institute for Water and Atmospheric Research (Niwa) tracks the risk of major saleyards being in the path of aerial plumes of the disease originating from piggeries in high-risk weather conditions.

Aerial spreading of the disease is most likely to happen in Canterbury in autumn and winter, when an inversion layer traps warmer air over a cooler land mass.

Using computer models, a team of five scientists plotted the potential course of the viral plumes. Weather records were analysed to predict conditions favouring the airborne spread of the disease in the three-month national study commissioned by Biosecurity New Zealand.

While airborne dispersal is uncommon, it is difficult to control and can have far-reaching consequences when the right weather conditions coincide.

Niwa mesoscale meteorologist Dr Richard Turner said the climatological-risk atlas would help Biosecurity New Zealand in its preparation to respond to an outbreak of the disease.

Scientists had assessed the weather conditions that would spread plumes of high levels of the virus emitted by animals, he said. "The best conditions for the aerial spread of viral plumes are similar to what produces an air-pollution event in Christchurch."

Risk maps have been produced for the five main pig-growing regions of Waikato, South Auckland, Taranaki, Manawatu and Canterbury. Piggeries were targeted because pigs are the biggest emitters of airborne plumes.

Nationally, airborne plumes are most likely to be spread on fine, clear nights, when winds are light and the humidity is more than 55 per cent.

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