News Release

Controlling schistosomiasis: buffalo or snails?

Peer-Reviewed Publication

PLOS

A parasitic infection common in China and Southeast Asia could be effectively reduced by controlling snail populations, according to research published in PLoS Medicine.

Infection with schistosomes of various species affects some 200 million people worldwide, and can cause serious chronic illnesses, including liver failure. Steven Riley of the University of Hong Kong and collaborators analyzed infection patterns of the parasitic worm Schistosoma japonicum in fifty villages in Samar Province, the Philippines. Rates of infection among humans and animals have been found to differ among villages, and the researchers developed a mathematical model incorporating fecal parasite test results from thousands of people and animals (including, cats, pigs, dogs, water buffalo, and rats) to explain these differences.

Schistosomes are passed from mammals to fresh-water snails via feces, and then cycle back to infect mammals that contact water inhabited by infected snails. Using the mathematical model, the team found that transmission from snails to mammals was a more important factor in explaining the differences among villages than transmission from mammals to snails.

As with all scientific models, the findings of this one depend on the assumptions made to build the model. Nevertheless, the findings suggest that interventions to reduce the size of the snail population and the exposure of mammals to parasite-containing water might reduce human infection levels more effectively than interventions that interrupt other parts of the parasite’s life cycle.

The results also indicate that the contribution of water buffaloes to human S. japonicum infection in the Philippines is not particularly important. This finding contrasts with a recent study that identified water buffalo as the major mammalian reservoir for S. japonicum in China. (http://www.who.int/bulletin/volumes/85/7/06-034033/en/index.html), and suggests that further studies of t he transmission of S. japonicum by water buffalo are warranted before efforts are dedicated to treat or vaccinate water buffalo as a control measure against human S. japonicum infection.

In a related perspective article, Song Liang and Robert Spear, who were not involved in the study, discuss the findings and conclude that the “modeling approach can be a useful tool in exploring schistosomiasis transmission in other settings, and may even apply to other macroparasites.”

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Citation: Riley S, Carabin H, Belisle P, Joseph L, Tallo V et al (2008) Multihost transmission dynamics of Schistosoma japonicumin in Samar Province, the Philippines. PLoS Med 5(1): e18.

IN YOUR COVERAGE, PLEASE LINK TO THIS URL, WHICH WILL PROVIDE ACCESS TO THE PUBLISHED PAPER: http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0050018

PRESS-ONLY PREVIEW OF THE ARTICLE: http://www.plos.org/press/plme-05-01-riley.pdf

Related image for press use: http://www.plos.org/press/plme-05-01-riley.jpg

Caption: Histopathological image of old state of schistosomiasis incidentally found at autopsy. The deposition of calcified eggs in the colonic submucosa suggests prior infection of Schistosoma japonicum.

CONTACT:

Steven Riley
Hong Kong University
Community Medicine and School of Public Health
5/F William MW Mong Block
21 Sassoon Road
Hong Kong, SAR 1111
China
+852 2819 9283
steven.riley@hku.hk

Related PLoS Medicine perspective article:

Citation: Liang S, Spear RC (2008) Model-based insights into multi-host transmission and control of schistomiasis. PLoS MEd 5 (1) e23.

IN YOUR COVERAGE, PLEASE LINK TO THIS URL, WHICH WILL PROVIDE ACCESS TO THE PUBLISHED PAPER: http://medicine.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pmed.0050023

PRESS-ONLY PREVIEW OF THE ARTICLE: http://www.plos.org/press/plme-05-01-liang.pdf

CONTACT:

Song Liang
Ohio State University
Division of Environmental Health Sciences
College of Public Health
Columbus, Ohio
United States
+1 614-293-8263
sliang@sph.osu.edu

About PLoS Medicine

PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit http://www.plosmedicine.org

About the Public Library of Science

The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org

Everything published by PLoS Medicine is Open Access: freely available for anyone to read, download, redistribute and otherwise use, as long as the authorship is properly attributed.


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