Fighting foot-and-mouth disease.

LONDON – According to a group of British scientists, the rapid, preemptive slaughtering of livestock that may be infected with foot-and-mouth disease is the best way to slow the epidemic.

“Ring culling,” the preemptive slaughter of all animals on farms bordering infection sites, dramatically reduces the spread of disease, scientists at London’s Imperial College School of Medicine reported last week.

Aggressive ring culling would help prevent the epidemic from spreading beyond the 45,000 farms within the areas currently classified as affected, the researchers said, using data provided by Britain’s Ministry of Agriculture, Fisheries and Food.

If it isn’t stopped, foot-and-mouth disease will ultimately threaten farms throughout Great Britain, they said.

Only option.

“Extensive culling is sadly the only option for controlling the current British epidemic, and it is essential that the control measures now in place are maintained during the long decay phase of the epidemic (several months) to ensure eradication,” the researchers wrote in the April 13 issue of Science.

Primary conclusions presented include:

* The faster that animals are slaughtered following the report of a suspected infection, the bigger the reduction of the epidemic.

* Even when infected animals are slaughtered within 24 hours after symptoms appear, some 30 percent of all U.K. farms will be affected by over the months-long course of the epidemic – unless preemptive ring culling is also implemented.

* An even more aggressive approach – slaughtering sick animals within 24 hours, followed by ring culling over a 1-mile area within 48 hours – would protect many more farms.

First reported in Great Britain in February this year, foot-and-mouth disease infects cloven-footed mammals including cattle, sheep, goats, and pigs. Adult animals may survive foot-and-mouth disease with permanently reduced weight or milk yield, but the disease can kill the young.

Logistical difficulties in processing large numbers of animals, and significant delays between reporting cases and culling of farms, are hindering efforts to fight foot-and-mouth disease, the authors note.

By 3 April, some 631,000 animals had been slaughtered, compared with 440,000 during the last foot-and-mouth disease epidemic, in 1967.

The latest outbreak, now believed to be approaching its peak, is expected to continue through the summer, scientists said.