Disease Spread in Age Structured Populations with Maternal Age Effects

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. 

epi model R script.R

This is the script for the SIR model as well as the associated script for life history data. 

main.body size.csv

This is the data for the body size data collected in the main experiment. This was measured using imageJ, was recorded in pixels and converted into millimetres. 

main.exposed.csv

This is the proportion of infected/not infected individuals from an exposed treatment group. This was a subset of individuals from the entire experiment. This was the result of the exposures from the main experiment. 

main.reproduction.csv

This document records reproduction for individuals from old or young mothers. It is a count of the offspring born at each reproductive event, which occurs generally every three days, though variation in interclutch interval increases with age. This was from the main experiment. Only those who were unexposed to the parasite, where used for this portion of the experimental work. 

sm.body size.csv

This records body size similarly to above, and was an independent replication of the main experiment. 

sm.infection status.csv

This is infection outcomes of exposures carried out as above, in an independent replication of the main experiment. 

sm.total babies.csv

This is the reproductive output, carried out similarly to above, but in an independent replication of the main experiment.