The Epidemiology of Soil-Transmitted Helminths in Bihar State, India

Citation: Greenland K, Dixon R, Khan SA, Gunawardena K, Kihara JH, Smith JL, et al. (2015) The Epidemiology of Soil-Transmitted Helminths in Bihar State, India. PLoS Negl Trop Dis 9(5): e0003790. doi:10.1371/journal.pntd.0003790
Published: May 20, 2015

Ascaris_infectionBackground: Soil-transmitted helminths (STHs) infect over a billion individuals worldwide. In India, 241 million children are estimated to need deworming to avert the negative consequences STH infections can have on child health and development. In February-April 2011, 17 million children in Bihar State were dewormed during a government-led school-based deworming campaign. Prior to programme implementation, a study was conducted to assess STH prevalence in the school-age population to direct the programme. The study also investigated risk factors for STH infections, including caste, literacy, and defecation and hygiene practices, in order to inform the development of complementary interventions.
Methods: A cross-sectional survey was conducted among children in 20 schools in Bihar. In addition to providing stool samples for identification of STH infections, children completed a short questionnaire detailing their usual defecation and hand-hygiene practices. Risk factors for STH infections were explored.
Results: In January-February 2011, 1279 school children aged four to seventeen provided stool samples and 1157 children also completed the questionnaire. Overall, 68% of children (10-86% across schools) were infected with one or more soil-transmitted helminth species. The prevalence of ascariasis, hookworm and trichuriasis was 52%, 42% and 5% respectively. The majority of children (95%) practiced open defecation and reported most frequently cleansing hands with soil (61%). Increasing age, lack of maternal literacy and certain castes were independently associated with hookworm infection. Absence of a hand-washing station at the schools was also independently associated with A. lumbricoides infection.
Conclusions: STH prevalence in Bihar is high, and justifies mass deworming in school-aged children. Open defecation is common-place and hands are often cleansed using soil. The findings reported here can be used to help direct messaging appropriate to mothers with low levels of literacy and emphasise the importance of water and sanitation in the control of helminths and other diseases.

Author Summary: Deworming is recognised as a cost-effective way to increase the educational attainment and health of school-age children who experience high prevalence and intensity of soil-transmitted helminth (STH) infections and bear the majority of the disease burden. STH transmission is driven by a number of factors including the environment, water availability and lack of sanitation. Previous government surveys in India revealed small geographic areas have extremely heterogeneous prevalence, generating interest in exploring what explains this heterogeneity. Having recently implemented a large deworming progamme, the government of Bihar State was keen to utilise the deworming campaign to undertake complementary activities to reduce transmission and establish an integrated approach to STH control. This paper presents the results of the prevalence and intensity cross-sectional survey and takes an exploratory look at the contribution of key risk factors to transmission. Maternal literacy, caste, open defecation (a common practice) and absence of handwashing stations at schools were associated with increased risk of hookworm or ascariasis. Using this information it is possible to hypothesise about potential key areas of focus during the deworming campaign and interventions that could complement deworming programmes, as well as to develop some key messages to accompany the next deworming programme in Bihar.


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