March 14, 2006

 

USDA confirms positive result on mad cow test

 

 

US Department of Agriculture Chief Veterinary Medical Officer John Clifford said Monday (March 13) that a cow in Alabama tested positive for mad cow disease.

 

Clifford said a positive result was returned from a Western-blot confirmatory test conducted at the USDA's laboratories in Ames, Iowa, on samples from an animal that had tested "inconclusive" on a rapid screening test performed on Friday.

 

The cow had spent the past year at an Alabama farm, Clifford said.

 

"The samples were taken from a non-ambulatory (downer) animal on a farm in Alabama," Clifford said in a conference call with reporters. A local private veterinarian euthanised and sampled the animal and sent the samples for further testing, which was conducted at one of our contract diagnostic laboratories at the University of Georgia. The animal was buried on the farm and it did not enter the animal or human food chains.

 

The suspect animal is said to be a Santa Gertrudis breed beef cow of uncertain age but believed to be more than 10 years old based on inspection of its dentition, or teeth.

 

"This would indicate that this animal would have been born prior to the implementation of the 1997 feed ban imposed by Food and Drug Administration (FDA). Older animals are more likely to have been exposed to contaminated feed circulating before the FDA's 1997 ban on ruminant-to-ruminant feeding practices, which scientific research has indicated is the most likely route for BSE transmission," he said.

 

"We are now working with Alabama animal health officials to conduct an epidemiological investigation to gather any further information we can on the herd of origin of this animal. The animal had only resided on the most recent farm in Alabama for less than a year," Clifford said.

 

He said USDA will be working to locate animals from the cow's "birth cohort and any offspring". He said USDA will also work with the FDA "to determine any feed history that may be relevant to the investigation".

 

Clifford said experience worldwide has shown that it is highly unusual to find BSE in more than one animal in a herd or in an affected animal's offspring. He added that all animals of interest will be tested for BSE.

 

He explained that under USDA testing protocols, surveillance samples are sent to contract laboratories for screening tests. If a sample is found to be inconclusive on the screening test, it is then shipped to the USDA's National Veterinary Services Laboratories (NVSL) in Ames, Iowa, for an additional rapid test and two confirmatory tests - the immunohistochemistry (IHC) test, which is conducted by APHIS scientists, and the Western blot test, which is conducted by scientists with USDA's Agricultural Research Service.

 

USDA considers an animal positive for BSE if either of the two confirmatory tests returns a positive result, the department's release said.

 

"In this instance, the inconclusive result from the contract lab in Georgia was confirmed through a second rapid test at NVSL.