Coinfection and the Evolution of Resistance: A Mathematical Analysis
MetadataShow full item record
This thesis investigates the effect of coinfection on the emergence of resistant pathogens. Firstly, a multiple infection model with treatment is derived and the conditions for invasion are established. The invasion condition is then related to an equivalent and easier to obtain condition, R0, by applying the Next-Generation Theorem. Due to its biological interpretation, a heuristic derivation of R0 as the invasion condition is also given. Then assuming that resistance comes at a cost to the pathogen, and using a very simple within-host model, we establish under which specific set of biological assumptions we should expect coinfection to increase or decrease R0. Specifically, we obtain that in the no cost of resistance case, reduced transmission case, and increased mortality case, that coinfection will increase the R0 value and that in the reduced growth and poor competitor case that the effect is indeterminate. We also introduced a method for approximating the intrinsic growth rate when the coinfection efficiency is assumed to be small. Using this method, we show that we obtain the same trend for the cost of resistance cases when comparing our estimate for the intrinsic growth rate for the coinfection case versus the intrinsic growth rate for the single infection case. We also use this approximation to estimate the percentage of resistance as a function of time. Finally, we analyze how both the intrinsic growth rate and R0 respond to a changing treatment rate, compared to the intrinsic growth rate and R0 value in the single infection case. We found that the change in R0 and the intrinsic growth rate can be greater or smaller than the change in R0 or the intrinsic growth rate for the single infection case.