Fig 1.
Stability of hypoendemicity and threshold biting rates (TBRs).
Three hundred repeat simulations of EPIONCHO-IBM were run for 500 years, determining the proportion of persistent runs with greater than 0% microfilarial (mf) prevalence. Panel A: Colours from dark red to light yellow indicate a decreasing proportion of model simulations persisting over time for different annual biting rate values (ABRs). Results are shown for a population of 400 individuals (N = 400) and inter-individual exposure heterogeneity parameter kE = 0.3, with the light blue box highlighting persistent proportions after 500 years of simulation. Panel B: Markers are the proportion of the 300 model runs persisting after 500 years for ABRs falling within the TBR range (i.e., > 0% and < 100% run persistence). The blue-highlighted box shows the proportion of persistent runs at the simulation endpoint as generated by the model parameters used in Panel A. Remaining boxes show different combinations of N and kE as indicated by the row and column labels, respectively.
Fig 2.
Rate of fade-out of onchocerciasis transmission within and below threshold biting rate (TBR) range.
The colour of each line corresponds to an annual biting rate (ABR; no. bites/person/year) for a population of N = 400 and kE = 0.3, with the rate of fade-out calculated by fitting a Weibull survivorship function (Eqn. 1, 2) to 300 EPIONCHO-IBM simulations (Fig C in S1 Text) from the final timepoint which gave 100% run persistence (i.e., all simulations > 0% microfilarial prevalence).
Fig 3.
Mean microfilarial (mf) prevalence dynamics within and below threshold biting rate (TBR) range.
The colour of each line corresponds to an annual biting rate (ABR; no. bites/person/year) for a population of N = 400 and kE = 0.3, with mean mf prevalence calculated from 300 EPIONCHO-IBM simulations. Dynamics are plotted from a 16% mf prevalence at time zero corresponding to the minimum mf prevalence with no fade-out over 500 years (i.e., zero rate of fade-out; Fig. 2). Mf prevalence declines more rapidly with decreasing ABR, but may persist (i.e., mf prevalence > 0%) for epidemiologically-relevant periods even at very low ABRs.