Vaccination protects ants from infections

Science: Ants brush their conspecifics to protect against infection

05/04/2012

Ants protect themselves by cleaning their conspecifics from infections that could otherwise become a threat to the entire colony. However, it is not the cleaning itself that shows the disease-preventing effects, but the minimal absorption of the pathogens as part of the cleaning process, report Professor Sylvia Cremer from the Institute of Science and Technology Austria (IST) in Klosterneuburg and colleagues.

The social contact with sick ants leads to an immune protection of the nest inhabitants, write the researchers around Prof. Sylvia Cremer of the institute OF Science and Technology in the specialized magazine „PLoS Biology“. Ants lick their infected conspecifics while cleaning and protect themselves by receiving minimal excitatory doses from a disease, the researchers write. The cleaning process thus acts as a kind of vaccine that prevents the spread of infections in the colony.

Collective hygiene protects ants from infection
Similar to cramped megacities, infection could easily spread to ant colonies even if the small animals do not have one „social immune system“ Prof. Sylvia Cremer explained that it protects against the diseases. The collective hygiene behavior of the ants and the associated recordings of small amounts of the pathogens form an efficient method for controlling infections, the IST researchers continue. If the animals did not protect themselves from disease in this way, infection could easily spread to the densely populated ants and in the worst case could mean the end of the entire colony. By licking the conspecifics during the cleaning process find a proper vaccination of animals instead. The sick animals are not avoided, but licked by the conspecifics, „to remove the pathogen from the body of the infested ants“, the researchers report to Prof. Sylvia Cremer. Because of this „social care behavior“ the survival chances of the affected individuals would be significantly increased. But also for the caring ants, cleaning the sick conspecifics, according to the IST researchers benefits.

Reduced risk of infection by cleaning sick conspecifics
Although the caring ants are at increased risk of infection through contact with the sick animals, they only receive such low doses of the pathogens that „only sublethal infections“ report, Prof. Cremer and colleagues report in the article „Social Transfer of Pathogenic Fungus Promotes Active Immunization in Ant Colonies“ . The scientists had observed the spread of fungal spores in an ant colony and found that during the cleaning process only a very small „Transfer of spores“ took place. By including low doses of infectious spores in healthy animals, the immune system was activated and they were henceforth protected from disease, according to Cremer and colleagues. In this way, the spread of infections is successfully prevented. Only two percent of the newly infected ants had died after exposure to the spores of the fungus Metarhizium, the remaining animals were immune, said the IST researchers. The infection protection of the ants works similarly to the vaccinations in humans. The „social dissemination of infectious particles at a low level“ offer a kind of „social immunization against fungal diseases in ant colonies“, so the conclusion of the scientists.

Social immunization as disease protection in humans?
Possibly, a similar social immunization could also affect humans, write Simon Babyan from the University of Edinburgh and David Schneider from Stanford in an accompanying article in the journal „PLoS Biology“. „By studying social immunity in insect colonies, we may be able to discover emergent properties that we have so far overlooked in another important social animal, the human“, emphasize babyan and tailor. According to the two commentators, the IST researchers used „a combination of methods to identify the mechanism of social immunization: mathematical models, behavioral biology, microbiological, immunological, and molecular techniques, all of which together provide an exciting proof-of-concept that group-level immunity can be experimentally manipulated and modeled.“ (Fp)

Picture: Erika Hartmann