U-S-D-A officials said on Wednesday tests seemed to indicate a third case of Mad Cow disease in the U.S. Iowa State University Extension Veterinarian Nolan Hartwig does not think the discovery signals a big undiscovered number of cases. He says they’ve been testing for quite a long time and did 200-thousand samples this year. So only finding this third one “tells us if it’s endemic across this country, it’s certainly at extremely low levels” according to Hartwig. The animal, which died giving birth, was reportedly 12 years old. “If we had to have a case,” Hartwig says, “it’s good that it’s a very old cow.” It can mean the exposure when it was young before current safety measures were in place. There also hasn’t been time to examine where the cow came from, if it was related to the first two, or got the brain-wasting ailment through herd contact, at a sale barn or through other sources of exposure. There are barriers in place that Hartwig says seem to work to halt the disease. He says the list includes not feeding byproducts from the rendering industry to cattle or other ruminants, not importing animals from countries where the disease is known to infect herds like the United Kingdom, and throwing away “specified risk materials” — that means the brain and nerve tissue from cattle that are slaughtered at over 30 months of age. The great fear is that the brain-wasting ailment will hit people who eat meat from the animals, but Hartwig says we don’t really need to worry. There’ve been about 150 cases of “variant” Creutzfeldt-Jakov disease, thought to be the human version of B-S-E, but not a single case in the U.S. Doctor Hartwig says “the great unknown” is if Mad Cow disease is relatively new, if its level has always been low, or if it’s been imported relatively recently to this country.