Ants avoid superinfections by performing risk-adjusted sanitary care

Abstract

Being cared for when sick is a benefit of sociality that can reduce disease and improve survival of group members. However, individuals providing care risk contracting infectious diseases themselves. If they contract a low pathogen dose, they may develop low-level infections that do not cause disease but still affect host immunity by either decreasing or increasing the host's vulnerability to subsequent infections. Caring for contagious individuals can thus significantly alter the future disease susceptibility of caregivers. Using ants and their fungal pathogens as a model system, we tested if the altered disease susceptibility of experienced caregivers, in turn, affects their expression of sanitary care behavior. We found that low-level infections contracted during sanitary care had protective or neutral effects on secondary exposure to the same (homologous) pathogen but consistently caused high mortality on superinfection with a different (heterologous) pathogen. In response to this risk, the ants selectively adjusted the expression of their sanitary care. Specifically, the ants performed less grooming and more antimicrobial disinfection when caring for nestmates contaminated with heterologous pathogens compared with homologous ones. By modulating the components of sanitary care in this way the ants acquired less infectious particles of the heterologous pathogens, resulting in reduced superinfection. The performance of risk-adjusted sanitary care reveals the remarkable capacity of ants to react to changes in their disease susceptibility, according to their own infection history and to flexibly adjust collective care to individual risk.

Ant colonies promote the diversity of soil microbial communities

“…However, they had a higher proportion of ant-microbial symbionts than surrounding bare soils including Aspergillus pseudonomius, Aspergillus NRRL-32683, Mucor circinelloides, and Cryptococcus laurentii, which are involved in the production of antibiotics [14]. These findings are in agreement with recent research [15], and suggest that ant nests maintain a hygienic environment in their nests.…”

Camponotus floridanus Ants Incur a Trade-Off between Phenotypic Development and Pathogen Susceptibility from Their Mutualistic Endosymbiont Blochmannia

“…During infection, M. brunneum can suppress the host immune system with secondary metabolites [ 42 ] and physically break host cells and tissues with its invading hyphae, which may allow B. floridanus to proliferate and escape bacteriocytes. This would require the host to elicit a multifaceted immune response involving both antifungal and antibacterial pathways of the innate immune system, analogous to a super-infection in insects where two distinct pathogens infect the host, hastening and increasing mortality [ 72 , 73 , 74 , 75 ]. Escaped B. floridanus in the haemocoel could thereby give the invading M. brunneum the upper hand in the battle against the host immune system.…”

Social immunity: why we should study its nature, evolution and functions across all social systems

“…In an elegant study conducted in the ant Lasius neglectus, however, Konrad et al [35] demonstrated that allogrooming provides direct benefits to both recipients and donors, as it allows donors to prime their own immune system and thus boost their defences against future pathogen exposure. Interestingly, a follow-up study recently showed that these direct benefits are pathogen-specific in that workers immune-primed with one type of pathogen preferentially direct their future allogrooming behaviours toward individuals infected with the same compared to a different pathogen [36].…”