Inferring infection processes of a parasitic nematode using population genetics.

The distribution of genetic differentiation in a population of the parasitic nematode Strongyloides ratti divided between rat hosts was determined. We applied population genetic theory to these data to determine the source of new infections. We estimate the rate at which a rat acquires a new infection from (a) the existing subpopulation of parasites within that rat ('self-reinfection') versus (b) the wider environment ('immigration'). We find that the observed levels of genetic diversity and differentiation in the study population are consistent with low to moderate rates of self-reinfection and inconsistent with high rates of self-reinfection.