US ‘rediscovers’ its second mad cow

17:03 13 June 2005
NewScientist.com news service

The US has found its second case of mad cow disease in a cow suspected, but cleared, of having BSE in November 2004. Although meat from the cow did not enter the food chain, the finding calls into question the accuracy of the country’s BSE surveillance programme. The cow might also be the first case born in the US.

The first US case was in a cow imported from Canada in 2003. In 2004 the country started testing “high-risk” cattle - those that show neurological symptoms, are found dead or are “downers” (unable to stand).

Since then it has tested 375,000 cattle. None were declared positive. In contrast, Canada has tested 30,000 cattle and found three positives. The rate at which the tests uncover positive cattle depends on the sample size, stresses Marcus Doherr of the University of Bern in Switzerland, who helped develop Swiss BSE surveillance.