Periodic Reporting for period 2 - EPIDEMIC (Experimental Epidemiology in Ant Societies)
Periodo di rendicontazione: 2021-08-01 al 2023-01-31
Social organisms live in dense aggregations where individuals engage in frequent interactions, which can facilitate pathogen transmission and increase the risk of disease outbreak. Understanding how disease spreads through social groups is therefore an important question with potential implications for public health. In social groups, the risk for any individual to become infected depends not only on that individual's own traits (for example, its age, genotype, and behaviour) but is also determined by traits of that individual’s social group (for example, group size and genetic composition, the immune status of group members, and the network of social interactions between group members). Most social groups are inherently complex and the experiments required to tease apart the relative importance of these factors in shaping disease outcomes often cannot be performed for practical and/or ethical reasons. In other words, it is often difficult to determine to what extent a given individual within a group becomes infected because of its genes, age, behavior, social environment, or interactions with others.
Theoretical epidemiology predicts that disease dynamics will depend in large part on a group's social interaction network, but empirical data are scarce. Experimental epidemiology is currently hampered by a lack of study systems enabling a rigorous investigation of the causal link between group composition, network structure and disease transmission. This project tackles this challenge using a novel system, the clonal raider ant, a social insect whose unique biology affords control over the main aspects of colony composition that are thought to modulate social network structure, and therefore, disease transmission. The approach will combine automated techniques for behavioral analyses with molecular tools, and will develop new methods to monitor pathogen transmission in real time. Capitalizing on this biological model and these tools, we will create experimental groups that are theoretically predicted to vary in transmission risk, inoculate these experimental groups with pathogens, and quantify infection propagation in real time. This will allow us to experimentally test some of the predictions from theoretical epidemiology, and to identify some of the properties of social groups that protect them against disease. By linking theoretical epidemiology to real-world disease dynamics, this project has the potential to improve our ability to predict disease dynamics in social groups.
Theoretical epidemiology predicts that disease dynamics will depend in large part on a group's social interaction network, but empirical data are scarce. Experimental epidemiology is currently hampered by a lack of study systems enabling a rigorous investigation of the causal link between group composition, network structure and disease transmission. This project tackles this challenge using a novel system, the clonal raider ant, a social insect whose unique biology affords control over the main aspects of colony composition that are thought to modulate social network structure, and therefore, disease transmission. The approach will combine automated techniques for behavioral analyses with molecular tools, and will develop new methods to monitor pathogen transmission in real time. Capitalizing on this biological model and these tools, we will create experimental groups that are theoretically predicted to vary in transmission risk, inoculate these experimental groups with pathogens, and quantify infection propagation in real time. This will allow us to experimentally test some of the predictions from theoretical epidemiology, and to identify some of the properties of social groups that protect them against disease. By linking theoretical epidemiology to real-world disease dynamics, this project has the potential to improve our ability to predict disease dynamics in social groups.
The action implementation has overall progressed according to plans. Four team members (two PhDs students, a postdoc, and the PI) have been active on EPIDEMIC in the reporting period. The first two work packages (WP1 and 2) are well underway (behavioral experiments have been performed, RNAseq data collected and analyzed) and have yielded two peer-reviewed publications. After some delays due to a change of host institution, hiring of a postdoc and methods development for WP3 started at the beginning of the second reporting period. No major problems were incurred.
While social insects are already recognized as good systems to experimentally study disease dynamics in a social context, three major limitations still hamper progress in this field: 1) the lack of repeatability and experimental control over social groups, which has limited the field to correlative studies with low sample sizes, 2) the lack of tools to efficiently monitor individual behavior in groups and describe social interaction networks, and 3) the limited availability of experimentally amenable natural parasites of social insects, in particular parasites allowing to monitor transmission in real time. As a result, there are to date few controlled experimental studies measuring disease spread in social interaction networks. To overcome the first limitation, we will establish the clonal raider ant, a species that combines the rich biology of insect societies with unprecedented experimental amenability, as a system for experimental epidemiology. The second limitation will be alleviated by the use and further development of automated behavioral analyses. To address the third limitation, we will establish a nematode that naturally infects clonal raider ants as a system to study transmission in real time.