Final Report Summary - SOCIALVACCINES (Social Vaccination in Ant Colonies: from Individual Mechanisms to Society Effects)
Diseases can spread quickly in well-interconnected social groups such as found in human metropolises or the colonies of social insects. To counteract this high risk of infection, social insects such as ants have evolved collective disease defences in addition to the individual immunity of all group members, thereby achieving "social immunity". Their social health care involves that pathogen-exposed individuals are regularly taken care of by their healthy group members that remove infectious particles from the body surface of exposed individuals by grooming. We could show that garden ants moreover apply their formic-acid rich poison – which they otherwise spray against nest intruders – onto exposed group members, allowing for additional chemical disinfection. The antimicrobial properties of formic acid are thus utilized by the ants in fighting microbes, similar to human usage in e.g. meat preservation in food industry.
Providing care of group members suffering from infectious disease comes at the risk of disease contraction by the helpers. We found that garden ants change their individual and mutually performed sanitary actions in a way to reduce the risk of contraction. Nevertheless, many nestmate ants were found to carry low levels of infections in their bodies after interacting with an infectious individual. Interestingly, these low-level infections typically do not cause disease but instead trigger immune gene expression that provides a protective immune stimulation reducing the risk of infection at a later pathogen challenge. This "social immunisation" is not unique to social insects, but finds parallels to contact immunity spreading e.g. after oral live polio vaccinations in human family groups. Moreover, ant societies therefore display similar health care as early human medicine that took advantage of the protective effect of low-level infections in the form of variolation against otherwise deadly diseases such as smallpox.
Providing care of group members suffering from infectious disease comes at the risk of disease contraction by the helpers. We found that garden ants change their individual and mutually performed sanitary actions in a way to reduce the risk of contraction. Nevertheless, many nestmate ants were found to carry low levels of infections in their bodies after interacting with an infectious individual. Interestingly, these low-level infections typically do not cause disease but instead trigger immune gene expression that provides a protective immune stimulation reducing the risk of infection at a later pathogen challenge. This "social immunisation" is not unique to social insects, but finds parallels to contact immunity spreading e.g. after oral live polio vaccinations in human family groups. Moreover, ant societies therefore display similar health care as early human medicine that took advantage of the protective effect of low-level infections in the form of variolation against otherwise deadly diseases such as smallpox.