U study: Farming may have aided Minnesota bird flu outbreak

Farmers who actively tilled fields near turkey barns in the early days of Minnesota's avian influenza outbreak last year may have unwittingly helped spread the virus, a new University of Minnesota study says.

Soil in those fields may have been contaminated with droppings from migrating birds believed to be a source of the highly pathogenic H5N2 avian influenza. The virus can survive cold temperatures in soil and the tilling may have created "airborne particles that could carry the virus," the university's Center for Animal Health and Food Safety said in the report posted Thursday.

The outbreak devastated more than 100 Minnesota turkey farms in 15 counties last spring, creating economic damage estimated at more than $647 million, including $172 million in lost wages, salaries, and benefits, according to a University of Minnesota Extension study.

Study authors urged caution when reading the findings, saying they should be viewed as "hypothesis-generating rather than confirmatory" and that more research was needed. 

They noted that while tilling may have played a role introducing bird flu to turkey barns, it likely had no role in spreading the flu from farm to farm.

The study also concluded:

• The outbreak "was initiated through multiple introductions either from wild birds and/or a contaminated environmental reservoir."

• The outbreak was fueled by biosecurity breaches and the intensity of the outbreak in areas where farms were concentrated.

• Rendering trucks used to dispose of dead birds were also likely a factor in the spread.

Researchers recommended that in fields near turkey barns farmers consider planting alfalfa or other crops that do not involve early spring tilling.

They also called on officials to ensure that rendering trucks be "thoroughly disinfected before moving between farms, and rendering bins should be placed away from the production barns."