* "main.body.size.csv" This is a document recording the body size of Daphnia magna from old or young mothers, at their day of birth. It is counted in pixels and converted to millimetres. This is from the main study. * "main.exposed.csv" This document records the proportion of the test group that are either infected or not infected. Only a subset of the offspring from old and young mothers is exposed. This is from the main study. * "main.reproduction.csv" This document records the number of offspring produced by individuals from old and young mothers. This is from the main study. * "sm.body size.csv" This is the body data for the offspring of old and young mothers as produced through an independent replication of the main study. * "sm.infection.status.csv" This is the proportion of infected/ uninfected individuals from an independent replication of the main study. * "sm.total babies.csv" This is the total reproduction of offspring from old and young mothers, data produced through an independent replication of the main study. * "epi model R script.R" This is the R script for the model and the associated work carried out on the life history data sets.

Fundamental ecological processes, such as extrinsic mortality, determine population age structure. This influences disease spread when individuals of different ages differ in susceptibility or when maternal age determines offspring susceptibility. We show that Daphnia magna offspring born to young mothers are more susceptible than those born to older mothers, and consider this alongside previous observations that susceptibility declines with age in this system. We used a susceptible- infected compartmental model to investigate how age-specific susceptibility and maternal age effects on offspring susceptibility interact with demographic factors affecting disease spread. Our results show a scenario where an increase in extrinsic mortality drives an increase in transmission potential. Thus, we identify a realistic context in which age effects and maternal effects produce conditions favouring disease transmission.