DES MOINES, Iowa—Officials announced Monday that they have identified bird flu in a commercial flock of 50,000 turkeys in northwest Iowa, the state’s second case of a virus that has been identified in multiple U.S. states. Iowa agriculture officials and the U.S. Department of Agriculture confirmed the case in Buena Vista County, about 100 miles north of the case identified March 1 in a backyard flock of 42 ducks and chickens in Pottawattamie County. Gov. Kim Reynolds signed a disaster proclamation for Buena Vista County to allow state resources to help with disposal of the affected flock and disinfection of the farm. Officials didn’t immediately disclose the number of birds involved. The emergency declaration also provides resources for tracking, monitoring and the rapid detection of bird flu. The turkeys have been killed and disposed of on the farm. A 6.2-mile control area has been established to limit traffic in and …