LANSING, Mich. (AP) — State officials have designated parts of five Michigan counties as a “potential high risk area” for bovine tuberculosis.

The Department of Agriculture and Rural Development says it took the step after four free-ranging whitetail deer tested positive for the disease, which can be fatal for animals.

The deer were located in Iosco, Oscoda, Presque Isle and Roscommon counties.

The designation requires bovine TB testing for all cattle and bison herds within a 6.2-mile radius of where the TB-positive deer was found.

Officials say testing is needed to see if the disease has spread from local deer to cattle or bison.