I got this in the mail from our local county "Mosquito & Vector Control District" regarding West Nile Virus: "The first part of the surveillance program is chickens. Chickens do not get sick from the virus, but a simple blood test can tell us if an infected mosquito bit them. This makes them an ideal tool for learning if the virus is present. There are 206 chicken flocks located throughout California that are operated by local vector control districts or other public health agencies. In Contra Costa County, we have five chicken flocks, which are located in Hercules, Martinez, Oakley, Knightsen, and Walnut Creek. Blood tests from these chickens are done twice a month to help us learn if the virus is present." Very interesting!!!