Fig 1.
Map showing the locations of the 222 villages for which data are available.
Fig 2.
Distributions of Loa loa prevalence (left panel), the proportion of individuals with infection levels greater than 8,000 microfilariae per ml blood (centre panel) and the proportion with infection levels greater than 30,000 microfilariae per ml blood (right panel), in the data from all 222 villages.
Fig 3.
Empirical cumulative distributions of the parasite levels in individuals from five randomly selected villages.
Fig 4.
Log-likelihood-ratio statistic D = 2(Lw − Lg), for 156 villages where Lw and Lg denote maximised log-likelihoods for Weibull and Gamma fits, respectively.
Fig 5.
Empirical (coloured lines and dots) and fitted (black lines) cumulative distributions of parasite levels for the five randomly selected villages shown in Fig 3.
Fig 6.
Village-specific estimates of log(ρ/(1-ρ)) (upper row) and of logλ (lower row) plotted against percent forest cover within a 5km radius (left column), elevation (centre column) and average temperature (right column).
Red lines show the fitted contributions to the multivariate regression model defined by Eqs (2), (3) and (4).
Table 1.
Log-likelihood-ratio statistics, D, degrees of freedom, df, and p-values, p, for candidate covariates in univariable analysis.
Fig 7.
Cumulative predictive distributions of T, the proportion of village residents with parasite count greater than c = 8000/ml, for the five randomly selected villages shown in Figs 3 and 5, based on the fitted model without covariates.
Dashed vertical lines show the point predictions. Black horizontal lines show equal-tailed 95% plug-in predictive intervals. Red horizontal lines show the corresponding 95% confidence intervals for the true proportions based on the binomial sampling distribution of the observed numbers of individuals in each village with parasite count greater than c = 8000/ml.
Fig 8.
Comparison of predictions using the reported point estimates of model parameters and taking into account the uncertainty around the estimated parameter values.
The upper row shows point predictions (left column) and prediction interval lengths (right column) for a high infection threshold c = 8,000. The lower row shows the corresponding comparsions for a threshold c = 30,000.
Fig 9.
Selected quantiles of the conditional probability distribution of the proportion of individuals with intensity of infection greater than c = 8,000 parasites per ml of blood (left-hand panel) or c = 30,000 parasites per ml of blood (right-hand panel), as functions of village-level prevalence.
The median (solid line) provides a “best guess” of the relationship between prevalence and proportion of highly infected individuals; the 2.5% and 97.5% quantiles indicate the imprecision of this best guess.