Earlier this year an outbreak of human infections of avian influenza A (H7N9) virus was reported in China. The Centers for Disease Control and Prevention expressed concern about H7N9, noting that “influenza viruses constantly change and it’s possible that this virus could become able to easily and sustainably spread among people, triggering a global outbreak of disease.”

Avian influenza, also known as bird flu, generally remains in the realm of birds and rarely infects humans, but when it does it is particularly deadly. Because of this, it’s a hot topic for researchers.

Now a team from Monell Chemical Senses Center and the U.S. Department of Agriculture discovered that infection with avian influenza alters fecal odors in mallards. With that in mind, the researchers wanted to see if they could train lab mice to distinguish between feces from infected and non-infected ducks.

Since infected ducks and other waterfowl generally do not exhibit any obvious symptoms of infection, identifying infected birds requires capturing them for swab samples or finding dead birds to test, reports The Guardian. If another animal could be trained to detect the smell in bird droppings, tracking the disease could be much easier.

The mice were trained by running a maze. Each time they found infected feces, they were rewarded. Eventually they learned to find the infected poop 90 percent of the time.

The role that odor plays is believed to be related to survival, but it’s unclear whether it’s survival for other members of the species, or for the pathogen itself.

"The fact that a distinctive fecal odor is emitted from infected ducks suggests that avian influenza infection in mallards may be 'advertised' to other members of the population," notes Bruce Kimball, Ph.D., a research chemist with the USDA National Wildlife Research Center stationed at the Monell Center.

"Whether this chemical communication benefits non-infected birds by warning them to stay away from sick ducks or if it benefits the pathogen by increasing the attractiveness of the infected individual to other birds, is unknown," he added.

Future studies will look into whether odor changes can be used for tracking bird flu in waterfowl, and researchers are particularly interested in whether the odor change is specific to the avian flu pathogen or if it is merely a basic response to a variety of pathogens normally found in birds.

The full results of the study were released in the journal PLOS ONE.

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Researchers train mice to sniff out avian influenza in duck poop
Scientists discover bird flu can be detected by fecal odor changes in infected ducks, give mice the job.