The alarm was raised yesterday when deputy chief veterinarian Bob Biddle admitted that despite efforts by veterinary, customs and agriculture department staff, the authorities had failed to find 24 cattle and buffalo that may be harbouring the mad cow virus.

Lost somewhere in the national herd, the animals are among 400 cattle and buffalo imported from Britain, France, Switzerland, Bulgaria and Germany during the 1980s. Since then, fears surrounding the spread of bovine spongiform encephalopathy led the authorities to track down the animals.

None of the others have displayed any signs of having contracted or carrying the fatal disease. 

Biddle updated a Senate estimates committee hearing on the situation yesterday, stressing that there was actually little risk that the animals had or are carrying BSE. Nevertheless he said it was disappointing that they could not be found.