A strain of avian flu has been found at a third commercial turkey farm in southern Indiana, state officials said Thursday.

The H5N1 strain of the virus now circulating spreads easily from wild bird droppings and can be carried into commercial flocks on the feet of workers or on equipment, which is why high-level biosecurity protocol has been activated across the country in commercial operations.

State Board of Animal Health spokeswoman Denise Derrer said Monday the last positive bird flu case was Jan. 16 in Dubois County, Indiana's top turkey-producing county.

Indiana's state veterinarian says a recent bird flu outbreak is a reminder of the importance of all buyers and sellers of poultry to follow state record-keeping rules.

Ten southern Indiana commercial turkey farms have tested positive for a strain of bird flu, prompting a response from state and federal authorities.

The National Institutes of Health's funding will allow comparative pathobiology professor Suresh Mittal to continue working on that vaccine.