Threshold curves for <i>Babesia microti</i> survival at different locations and mouse infection prevalences with <i>Borrelia burgdorferi</i> strain BL206.

<p>This figure shows differences in threshold curves, representing where <i>R</i>₀ = 1, and associated 95% confidence intervals (dotted curves), that separate regions of <i>s_N</i> and <i>c</i> where <i>B. microti</i> is expected to emerge and regions where it is expected to fade out. Threshold curves are contour curves where <i>R</i>₀ is plotted as a function of two variables: the proportion of fed infected larvae that survive to become infectious feeding nymphs, <i>s_N</i>, and the proportion of ticks feeding on <i>Peromyscus leucopus</i>, <i>c.</i> Plots indicate effects of location specific (Block Island and Connecticut) timing of tick activity as well as <i>B. burgdorferi</i> strain BL206 strain prevalence in mice (low = 0.3 and high = 0.8) on <i>R</i>₀. Coinfection significantly enhances the likelihood of <i>B. microti</i> establishment in Connecticut and on Block Island when <i>B. burgdorferi</i> prevalence among <i>P. leucopus</i> is high (0.80) (confidence bounds do not overlap). Differences in threshold curves for <i>B. burgdorferi</i> strain B348 are shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115494#pone.0115494.s003" target="_blank">S3 Fig</a>.