Schistosomiasis Causes More Damage Than Previously Thought

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Main Category: Tropical Diseases
Also Included In: Infectious Diseases / Bacteria / Viruses;  Public Health
Article Date: 15 Mar 2008 - 0:00 PDT

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The health burden of an Asian strain of the parasitic flatworm schistosomiasis is more damaging to the global health burden than previously thought, according to a study published on March 5, 2008 in the open-access journal PLoS Neglected Tropical Diseases.

Schistosomiasis, a parasitic flatworm of the genus Schistosoma, can localize in several parts of the body but commonly affects the intestines. Symptoms include abdominal pain, fever, cough, diarrhea, abnormally high eosinophil count, and enlargement of the liver and spleen, and it is transmitted through certain species of snails. It primarily infects people in developing countries, infecting an estimated 207 million people in 76 (mostly developing) countries. There are several species of the Schistosoma genus that affect humans -- this study focused on Schistosomiasis japonica, found in China and the Philippines.

Through the Global Burden of Disease project, the World Health Organization (WHO) estimates the incidence, prevalence, severity, and length of over 130 major causes of illness, injury, and death throughout the world. A statistical measure known as the disability-adjusted life year (DALY) is used, which means to estimate the number of years of life lost due to premature death and any years lost in disability. This data is often used by policy makers to determine the level of funding for prevention programs, treatment efforts, and research.

According to the WHO, schistosomiasis has a low disease burden, with a 0.005 DALY score on a scale of 0 (for perfect health) to 1 (for death.) However, the burder of schistosomiasis has not been examined in more than a decade. To this end, the researchers performed a literature search to find data, and a decision model approach to re-examine the burden of this disease.  The researchers calculated that the symptoms of Schistosomiasis japonica is 7 to 46 times greater than the current estimate. The team arrived at an estimate of 0.098 to 0.186. This study is the first to focus on one strain of the disease, and it is part of an ever growing group of evidence that this common parasitic disease is more damaging than previously estimated for global health.

"Schistosomiasis has a detrimental impact on nutrition and growth and development and can lead to major organ damage and death," study author Julia Finkelstein , of the Harvard School of Public Health, Boston, USA, says. "Current measures may severely underestimate the disability-related impact of the infection and need to be revised."

Dr. Charles King, of Case Western Reserve University, Cleveland, USA, who was not involved in the study but wrote an accompanying Expert Commentary article, predicted that, "Ultimately, these new measures of schistosomiasis-associated disability will translate into a greater priority to control schistosomiasis." Integrating new approaches and discoveries with these old estimates will, he says,"be essential to providing a balanced and fair assessment of neglected tropical diseases, and for properly setting disease control priorities for these disabling diseases of poverty."

About PLoS Neglected Tropical Diseases

PLoS Neglected Tropical Diseases (http://www.plosntds.org/) is a peer-reviewed, open-access journal devoted to the pathology, epidemiology, prevention, treatment, and control of the neglected tropical diseases, as well as public policy relevant to this group of diseases. All works published in PLoS Neglected Tropical Diseases are open access, which means that everything is immediately and freely available subject only to the condition that the original authorship and source are properly attributed. The Public Library of Science uses the Creative Commons Attribution License, and copyright is retained by the authors.

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.

Decision-Model Estimation of the Age-Specific Disability Weight for Schistosomiasis Japonica: A Systematic Review of the Literature
Julia L. Finkelstein, Mark D. Schleinitz, Helene Carabin, Stephen T. McGarvey
PLoS Negl Trop Dis 2(3): e158.
doi:10.1371/journal.pntd.0000158
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Written by Anna Sophia McKenney
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