Social Immunization

Ant colonies make for great studies of social behavior. And incredible new findings appearing this week in PLoS Biology­ add to those previous studies—ants that work together to immunize the entire colony against a pathogen.

Scientific American sets the stage:

Researchers have found that when some members of an ant colony are exposed to a pathogen for the first time, all members of that colony—even the ones that were not initially infected—build resistance to the pathogen. How this happens was never clear.

Researchers in Austria and Germany investigated this by infecting a small number of ants in a colony with fluorescent-dyed fungal spores. Instead of avoiding the infected members, healthy ants licked them to remove the pathogen from the exposed ants’ bodies. This social grooming behavior not only increased the survival chances of exposed individuals, but also immunized the helper ants from contracting the disease.

As co-author Sylvia Cremer tells Scientific American:

Even though 60 to 80 percent of nest mates contracted the disease, only about 2 percent of the ants died. Such low-level infections were actually beneficial because they saved the directly exposed ants and built up resistance in the healthy ants.

For these ants, it’s all about survival of the colony. Scientists believe that this behavior may also be common in other social insects—from bees to termites. And an accompanying article in PLoS Biology goes a step farther:

By studying social immunity at a system level in insects perhaps we can find emergent properties that we have been missing in another important social animal—the human.

Image courtesy of Institute of Science and Technology Austria