Social Transfer of Pathogenic Fungus Promotes Active Immunisation in Ant Colonies

Abstract

Social contact with fungus-exposed ants leads to pathogen transfer to healthy nest-mates, causing low-level infections. These micro-infections promote pathogen-specific immune gene expression and protective immunization of nest-mates.

Opposing effects of allogrooming on disease transmission in ant societies

“…ants-as well as termites-rarely contract the disease and die after contact with Metarhizium-exposed nest-mates [21,32,39,40]. For L. neglectus, this fraction was as low as 2% (3/150 [32]) at the present pathogen dose, which is equivalent to a lethal dose of approximately 60% when applied to L. neglectus ants in the absence of social interactions (mortality isolated ants ).…”

“…We use a basic model similar to Konrad et al [32], but here focus on the contraction of disease, i.e. neither addressing the effect of immunization (as in [32]) nor the effect of pathogen spread per se (as in [36]).…”

“…We use a basic model similar to Konrad et al [32], but here focus on the contraction of disease, i.e. neither addressing the effect of immunization (as in [32]) nor the effect of pathogen spread per se (as in [36]). We thereby model disease spread in the colony as the fraction of infectious versus susceptible ants, which represents the final outcome of the pathogen interacting with the combined individual and collective, behavioural and physiological anti-pathogen defences of the hosts.…”

“…reproductive division of labour), they may still provide us important insights into how general factors affect disease spread within a society. Thus, recently, a few studies have developed epidemiological models to investigate how disease transmission in insect societies can be affected by (i) social organization and interaction networks [17], (ii) mobility and density of infectious individuals and nest architecture [30], (iii) individual and social immunity and nest hygiene [31] and (iv) immunization of nest-mates through social contact to exposed individuals [32]. However, these studies did not base their models on experimentally observed interaction rates under pathogen presence.…”

Fungal disease dynamics in insect societies: Optimal killing rates and the ambivalent effect of high social interaction rates

“…Even more, low-level infections may interfere with the predictions. Recently, it was shown that lowlevel infections with Metarhizium acquired by social contact in social insect colonies can lead to a protective immune stimulation Konrad et al (2012). This may well be true also for solitary individuals.…”