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bioRxiv · 10.1101/2022.12.07.519457

Parasite transmission in size-structured populations

Shaw, K.·Cloud, R.·Syed, R.·Civitello, D.
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Abstract

Host heterogeneity can impact parasite transmission, but determining underlying traits and incorporating them into transmission models remains challenging. Body size is easily measured and influences numerous ecological interactions, including transmission. In the snail-schistosome system, larger snails have a higher exposure to parasites but lower susceptibility to infection per parasite. We quantified the impact of size-based heterogeneity on population-level transmission by conducting transmission trials in differently size-structured snail populations and competing size-dependent transmission models. Populations with greater proportions of large snails had lower prevalence, and small snails were shielded from infection by co-occurring large conspecifics. Using the winning size-explicit model, we then estimated that schistosome transmission varies dramatically across time due to seasonal changes in snail population size structure. Thus, incorporating traits such as body size, which are impacted by and directly affect host ecology, into transmission models could yield insights for natural dynamics and disease mitigation in many systems. Open Research StatementAll experimental data and novel code used for data analysis are currently available on Figshare via this private link: https://figshare.com/s/7d70b88220b912e7eec5. Data will be made public on Figshare upon acceptance. Data set utilized for Figure 4 are from the following source: Rumi, A., D. Gutierrez Gregoric, and A. Roche. 2009. Tendencias Del Crecimiento Individual en Poblaciones Naturales de Biomphalaria spp. (Gastropoda, Planorbidae) en la Cuenca del Plata, Argentina. Comunicaciones de la Sociedad Malacologica del Uruguay. URL: https://www.redalyc.org/articulo.oa?id=52414008002 O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/519457v2_fig4.gif" ALT="Figure 4"> View larger version (22K): org.highwire.dtl.DTLVardef@18be9forg.highwire.dtl.DTLVardef@8ad57eorg.highwire.dtl.DTLVardef@c674b6org.highwire.dtl.DTLVardef@11876df_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 4.C_FLOATNO Predicted infection success of a single schistosome parasite given exposure of a snail in a natural population with varying body size structure over time. A) Distribution of body sizes from a population of Biomphalaria tenagophilia in del Plata Basin, Argentina from 2000-2001(Rumi et al. 2009). Number of snails sampled at each timepoint represented as n=. B) Points are the mean {+/-} 95% confidence interval of the predicted infection success of a single schistosome introduced into this snail population from simulated transmission trials using the fully size-dependent model. Grey line is the predicted successful infection from a transmission model that ignores size-based exposure and susceptibility. Substantial changes in snail population size structure cause month-to-month estimates of schistosome success to diverge substantially from predictions that ignore size dependence. In particular, the size-null prediction tends to overestimate schistosome success except at the times in which the population is heavily dominated by small snails. C_FIG

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Shaw, K., Cloud, R., Syed, R., Civitello, D.. 2022-12-11. Parasite transmission in size-structured populations. https://doi.org/10.1101/2022.12.07.519457

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