, who operates a dairy just outside the Novato city limits with her husband, said a cow testing positive for mad cow disease in California's Central Valley is no cause for concern.
Although the latest discovery of bovine spongiform encephalopathy in a Hanford, Calif., cow was the fourth time it was found in the United States, no humans were at risk, Grossi said. Mad cow diseases cannot be transmitted through milk.
"U.S. farmers and ranchers have done a fantastic job controlling this disease," said Grossi, who writes a popular blog about her life at the dairy.
In 2011, there were only 29 worldwide cases of BSE, a dramatic decline and 99 percent reduction since the peak in 1992 of 37,311 cases.
Officials at the U.S. Department of Agriculture told the AP the infected cow, discovered at a Central California rendering plant, was not bound for the food supply and is not indicative of a larger problem.
"There really is no cause for alarm here with regard to this animal," John Clifford, chief veterinary officer for the department, told the AP.
Clifford later issued a statement on behalf of the USDA, saying in part, "USDA remains confident in the health of the national herd and the safety of beef and dairy products."
The California cow did not acquire the disease from tainted feed, the USDA says, and veterinary experts told the AP a random brain mutation was the likely culprit. In the 1990s, a new law prohibited any feed with animal byproducts to be fed to cattle.
The United States tests about 40,000 cows per year for mad cow disease, a lower percentage of the herd than in other countries. Japan, for example, tests every cow destined for human consumption and has found more than 30 cases of the disease since 2001.
Reuters reports the Chicago live cattle futures market fell as news of the infected cow spread Tuesday, but rebounded after federal officials said the food supply was safe.
The disease was last seen in the U.S. in 2006 and is caused by misfolded proteins in a cow's brain.
A fatal human version of BSE, Creutzfeldt-Jakob disease, can spread to people who consume diseased meat. In February, a Marin woman died and a second resident got sick with a rare degenerative brain disorder occasionally associated with mad-cow disease, according to this story in the San Francisco Chronicle. Neither case was infectious and there was no public health threat.
The Huffington Post reported Tuesday that the discovery of mad cow is unwelcome news for an industry already struggling with weakened demand over record high beef prices stemming from a perfect storm of drought and foreign demand, along with public outrage over "pink slime."
Dairy farmers of Marin, does this new report of mad cow disease concern you? Consumers, will it make you think twice about drinking milk or eating beef? Tell us in the comments.
— Novato Patch's Brent Ainsworth and several other Patch editors contributed to this report.