While the primary sources of AI are waterfowl and migratory birds, it’s not known exactly how the virus gets from wild birds to commercial poultry, Sato told Poultry Health Today.

Sato said her research project started at the tail end of the 2015 AI outbreak in Iowa. Investigators collected samples from layer farms that broke with the disease; they also checked the feed bins for contamination.

The next step was establishing if feed was a vector for transmitting the virus. They evaluated complete layer mash, along with individual components of the feed, she said.

Sato found the AI virus is not very stable in the feed and doesn’t persist well, although moisture can increase its stability. Heat or formaldehyde treatments can likely inactivate the AI virus, although there’s no silver bullet, Sato emphasized.

Some of Sato’s research collaborators at Iowa State University conducted the same type of research on the role feed played in the transmission of porcine epidemic diarrhea virus, which hit the US pork industry in 2013 and spread like wildfire. In this case, feed was found to be a vector.

Sato’s research involving layer farms indicates that bird-to-bird transmission and human traffic still appear to be the main ways the AI virus spreads, she said.

These results indicate that biosecurity remains the best defense against AI. Producers are maintaining strong biosecurity, but vigilance must continue to be a priority. There can’t be any weak links, Sato cautioned.