The reemergence of mad cow disease, discovered in a California dairy cow, could have major implications for the state’s meat industry, even though officials have said that the human food supply is unaffected.

Bovine spongiform encephalopathy hasn’t been found in U.S. since 2006 and was discovered in only three instances before then. But the disease has dealt a crippling blow to the industry in the past, especially when foreign countries refused to import American beef when mad cow was first uncovered in 2003.

The U.S. Department of Agriculturetests about 40,000 cows a year in its effort to catch the disease.

In California, private and public ranching takes up about 38 million acres, according to the California Cattlemen’s Assn. There are about 620,000 beef cows on 11,800 California ranches. The state also hosts 1.84 million dairy cows, according to information compiled by the California Beef Council.