The US Department of Agriculture has said a suspected BSE sample has been sent to the UK for further testing after two separate tests gave different results.

The USDA said that since its enhanced surveillance program for BSE began in June 2004, more than 375,000 animals from the targeted cattle population have been tested for BSE using a rapid test. Three of these animals tested inconclusive and were subsequently subjected to immunohistochemistry, or IHC, testing. All three inconclusive samples tested negative using IHC.

However, last week, the USDA's Office of the Inspector General (OIG), which has been partnering with the Animal and Plant Health Inspection Service, the Food Safety and Inspection Service, and the Agricultural Research Service by impartially reviewing BSE-related activities and making recommendations for improvement, recommended that all three of these samples be subjected to a second test, the OIE-recognised SAF immunoblot test, often referred to as the Western blot test. Of the three samples, two were negative, but the third came back reactive.

"Because of the conflicting results on the IHC and Western blot tests, a sample from this animal will be sent to the OIE-recognised reference laboratory for BSE in Weybridge, England. USDA will also be conducting further testing, which will take several days to complete," said the USDA's Dr John Clifford.

The sample was from a non-ambulatory (downer) animal and as such was banned from the food supply. It was processed at a facility that handles only animals unsuitable for human consumption, and the carcass was incinerated.

"After we receive additional test results on this animal, we will determine what further steps need to be taken and what changes, if any, are warranted in our surveillance program," Clifford added.