DOI: 10.5061/dryad.q83bk3jn6
title: Liver fluke (Opisthorchis viverrini) worm burdens and egg counts from humans in Thailand and Lao PDR

description: Helminth transmission and morbidity are dependent on the number of mature
 parasites within a host, however, observing adult worms is impossible for
 many natural infections. An outstanding challenge is therefore relating
 routine diagnostics, such as faecal egg counts, to the underlying worm
 burden. This relationship is complicated by density-dependent fecundity
 (egg output per-worm reduces due to crowding at high burdens) and the
 skewed distribution of parasites (majority of helminths aggregated in a
 small fraction of hosts). We address these questions for the carcinogenic
 liver fluke Opisthorchis viverrini, which infects approximately ten
 million people across Southeast Asia, by analysing five epidemiological
 surveys (n = 641) where adult flukes were recovered. Using a mechanistic
 model, we show that parasite fecundity varies between populations, with
 surveys from Thailand and Laos demonstrating distinct patterns of egg
 output and density-dependence. As the probability of observing faecal eggs
 increases with the number of mature parasites within a host, we quantify
 diagnostic sensitivity as a function of the worm burden and find that
 &gt; 50% of cases are misdiagnosed as false negative in communities
 close to elimination. Finally, we demonstrate that the relationship
 between observed prevalence from routine diagnostics and true prevalence
 is non–linear and strongly influenced by parasite aggregation.
description: This dataset brings together individual-level worm and egg data
 on human infections with the liver fluke <em>Opisthorchis
 viverrini</em> from five previously published epidemiological
 surveys. Further details are provided in the published article (Crellen T. <em>et al.</em> Diagnosis of helminths depends on worm fecundity and the distribution of parasites within hosts. 2023 <em>Proc. Roy. Soc. B</em>) Original data sources: Sithithaworn, P., Tesana, S., Pipitgool, V., Kaewkes, S., Pairojkul, C., Sripa, B., Paupairoj, A. and Thaiklar, K. 1991. Relationship between faecal egg count and worm burden of <em>Opisthorchis</em> <em>viverrini</em> in human autopsy cases. <em>Parasitology</em>, 102(2), pp.277-281 Ramsay, R.J., Sithithaworn, P., Prociv, P., Moorhouse, D.E. and Methaphat, C. 1989. Density-dependent fecundity of <em>Opisthorchis</em> <em>viverrini</em> in humans, based on faecal recovery of flukes. <em>Transactions of the Royal Society of Tropical Medicine and Hygiene</em>, 83(2), pp.241-242. Elkins, D.B., Sithithaworn, P., Haswell-Elkins, M., Kaewkes, S., Awacharagan, P. and Wongratanacheewin, S. 1991. <em>Opisthorchis</em> <em>viverrini</em>: relationships between egg counts, worms recovered and antibody levels within an endemic community in northeast Thailand. <em>Parasitology</em>, 102(2), pp.283-288. Haswell-Elkins, M.R., Satarug, S., Tsuda, M., Mairiang, E., Esumi, H., Sithithaworn, P., Mairiang, P., Saitoh, M., Yongvanit, P. and Elkins, D.B. 1994. Liver fluke infection and cholangiocarcinoma: model of endogenous nitric oxide and extragastric nitrosation in human carcinogenesis. <em>Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis</em>, 305(2), pp.241-252. Sayasone, S., Vonghajack, Y., Vanmany, M., Rasphone, O., Tesana, S., Utzinger, J., Akkhavong, K. and Odermatt, P. 2009. Diversity of human intestinal helminthiasis in Lao PDR. <em>Transactions of the Royal Society of Tropical Medicine and Hygiene</em>, 103(3), pp.247-254. 
description: The file is a comma-separated plain text file (.csv) with a
 header and six columns. The file can be viewed using a plain text viewer
 (e.g. Notepad in Windows or TextEdit in MacOS). To analyse the data, it is
 advisable to import it into statistical software such as R. 
 Code to run models which analyse the data can be found at the
 GitHub repository - https://github.com/tc13/worm-inference