Healthy ants that rub up against infected counterparts or even lick pathogenic fungal spores off them may be immunizing themselves and, ultimately, protecting their whole colony.

Credit: M. KONRAD/IST AUSTRIA

Sylvia Cremer at the Institute of Science and Technology Austria in Klosterneuburg and her colleagues infected ants (Lasius neglectus; pictured) with fluorescently labelled fungal spores (Metarhizium anisopliae) and released them among healthy members of their colony. The authors found that spores frequently transferred to healthy ants, resulting in low-level infection. Genetic analysis revealed that these minor infections upregulated a set of immune-system genes that bolstered the ants' anti-fungal defences.

Computer modelling suggests that this 'social immunization' actively stimulates the ants' immune systems, allowing the colony as a whole to fight infection.

PLoS Biol. 10, e1001300 (2012)