Supplementary Material

Figure. S1. Locations in grey were MVM locations where in-situ temperature data were available, but were not joined to our site data.

Figure. S2. Performance of the model throughout the year across thirty years of data. The points cluster for the excluded site, Norrhultsbäcken, visible in the lower half of the plot, demonstrates where the temperature processes were not captured by SHYPE due to wastewater treatment interference.

Figure. S3. Temperature residuals SMHI modelled water temperatures vs MVM in-situ measurements since 1991, Norrhultsbäcken removed from the dataset.

Figure. S4. Population level data for Renal hyperplasia and parasite load arranged by temperature rank, dashed line indicates the minimum renal hyperplasia score for PKD.

Figure. S5. Scatter plots comparing the variables of a. Mean water temperature and renal hyperplasia, coloured by log-transformed parasite load. Uninfected individuals are represented by light grey points. The posterior mean and 95% credible intervals of the first change point are visualised as vertical lines and shaded bands, respectively. b. mean parasite load (log-transformed) with within-site infection prevalence, point colour considers the mean water temperature. c. Mean water temperature and parasite load (log-transformed) at an individual level, where colour denotes the extent of the individual’s renal hyperplasia. d. Individual parasite load and renal hyperplasia with mean water temperature indicated by point colour. For a. and d. PKD threshold is illustrated by a dashed horizontal line.

Figure. S6. MCMC chains and density plots for each of the parameters in the mcp changepoint model.

Figure. S7. Spatial random effects from the spatial mixed-effects model of renal hyperplasia. The map shows the estimated spatial random field (ω_s) from the spatial mixed-effects model, representing residual spatial variation in renal hyperplasia after accounting for temperature, parasite load, their interaction, and site-level random effects. Values are shown on the link (log) scale. Positive values (blue) indicate areas where renal hyperplasia is higher than expected based on fixed effects alone, whereas negative values (red) indicate lower-than-expected values.

Table. S1. Summary statistics for temperature residuals between SMHI modelled temperatures and MVM in-situ measurements.

Table. S2. Global Moran’s I statistics for spatial autocorrelation of infection prevalence, parasite load and renal hyperplasia. Observed Moran’s I values were calculated using an adaptive Gaussian kernel with k nearest neighbours.

Table. S3. Fixed-effect parameter estimates from the spatial mixed effects model explaining renal hyperplasia. Estimates are reported on the link scale. Confidence intervals represent 95% confidence intervals.

© D. Philpott et al., Published by EDP Sciences 2026