Elsevier

Acta Tropica

Volume 172, August 2017, Pages 132-138
Acta Tropica

Establishment of first engineering specifications for environmental modification to eliminate schistosomiasis epidemic foci in urban areas

https://doi.org/10.1016/j.actatropica.2017.04.031Get rights and content

Highlights

  • First establishment of an engineering specification for snail control.

  • Environmental modification can change the environment of snail breeding completely.

  • Snail control effect of environmental modification in this study can withstand floods.

  • Environmental modification combine with mollusciciding can eliminate snails.

Abstract

Snail control is a key link in schistosomiasis control, but no unified methods for eliminating snails have been produced to date. This study was conducted to explore an engineering method for eliminating Oncomelania hupensis applicable to urban areas. The engineering specifications were established using the Delphi method. An engineering project based on these specifications was conducted in Hankou marshland to eliminate snails, including the transformation of the beach surface and ditches. Molluscicide was used as a supplement. The snail control effect was evaluated by field investigation. The engineering results fulfilled the requirements of the design. The snail density decreased to 0/0.11 m2, and the snail area dropped to 0 m2 after the project. There was a statistically significant difference in the number of frames with snails before and after the project (P < 0.05). Snails were completely eliminated through one year of continuous monitoring, and no new snails were found after a flood disaster. This study demonstrates that engineering specifications for environmental modification were successfully established. Environmental modification, mainly through beach and ditch remediation, can completely change the environment of Oncomelania breeding. This method of environmental modification combined with mollusciciding was highly effective at eliminating snails.

Graphical abstract

The establishment of engineering specification for environmental modification to eliminate the schistosomiasis epidemic foci and verification of its effect.

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Introduction

Schistosomiasis is widely distributed throughout the world and remains a serious public health problem in many countries (Li et al., 2000). Schistosomiasis mainly spreads in the developing countries of Africa, Asia and South America, which are poor and agriculturally based, and at least 90% of the world’s patients live in Africa (Dawaki et al., 2015, Hotez and Kamath, 2009, Vicente et al., 2016). According to WHO statistics, 240 million people in 78 countries are currently infected with schistosomiasis, and 779 million people are at risk of infection (PJ and G, 2009, WHO, 2002, Yang et al., 2015), making the burden of disease 70 million disability-adjusted life years (King and Dangerfield-Cha, 2008). With the growth of immigration and a continuously changing environment, the global schistosomiasis epidemic is going to produce a more serious disease burden and economic loss in the future (Fang et al., 2008, Finkelstein et al., 2008, King et al., 2005, van der Werf et al., 2003).

The prevalence of schistosomiasis is strongly related to social and economic conditions (Gazzinelli et al., 2006). Schistosomiasis in rural areas has been the focus of research and governance for many years. In contrast, research in cities is very rare, and the content and scope of the research are relatively concentrated (Firmo et al., 1996). Migration from rural to urban environments is prompting the constant expansion of urban schistosomiasis. At present, urban imported schistosomiasis infection occurs frequently throughout the world, and the residual snails breed often. Urban schistosomiasis is becoming an increasingly serious public health problem (HZ, 2002, Mott et al., 1990). Some studies have indicated that urban areas in Africa and South America have become foci of schistosomiasis transmission (Blanton et al., 2015, Mott et al., 1990).

The eradication of schistosomiasis must involve simultaneous transmission control and drug treatment. Snail control is a necessary method to achieve transmission control, especially in low-prevalence areas, and the final elimination of schistosomiasis can only occur through snail control (Sokolow et al., 2016, WHO, 1985, Yuan et al., 2005). Environmental modification, a long-term snail control method, has a more consolidated effect than other methods, and it saves resources and produces limited environmental pollution (YY et al., 2006). After an analysis of geographical conditions and economic capacity, this method is very suitable for the prevention and control of schistosomiasis in urban areas. Schistosomiasis in China is caused by Schistosoma japonicum. Oncomelania hupensis, its unique vector, is operculate and amphibious. In China, 5 of 12 provinces have eliminated schistosomiasis japonica through a method combining environmental modification and mollusciciding (Chen, 1999). Combined with health education, treatment and prevention measures, the improvement of sanitation and the water supply system on the basis of environmental modification and mollusciciding will achieve a better transmission control effect (Li et al., 2007).

Previous environmental modification projects have achieved remarkable snail control effects (Ault, 1994, Xu et al., 2015), but these methods have not been widely used globally. There are no unified engineering technical routes and engineering standards due to an ineffective interdisciplinary combination of schistosomiasis control and engineering technology. Even worse, schistosomiasis control studies are at a serious stage of stagnation in large and medium-sized cities. According to the survival characteristics of Oncomelania hupensis, this study was devoted to the exploration of engineering specifications for environmental modification in schistosomiasis epidemic foci to eliminate Oncomelania hupensis. This method could be widely applied to large and medium-sized cities after being scientifically adjusted for different geographical features.

Section snippets

Study site and population

Hankou marshland, the largest river beach cultural park in Asia, is located in Wuhan City, Hubei Province, China. This marshland, which is adjacent to the Yangtze River, is 8.45 km in length with an area of 1.6 million square meters. Hankou marshland is divided into two parts by the river embankment. The upper part is an artificial park suitable for leisure and entertainment. The lower part comprises a beach, reeds and weed growth. The natural scenery of the lower part attracts many visitors,

Risk assessment of schistosomiasis

In spring, the average density of living snails was 0.993/0.11 m2, the highest density was 76/0.11 m2, the positive rate of snails was 1.18%, the positive rate of mouse feces was 0.23%, and the positive rate of wild feces was 0.81%. In summer, the average density of living snails was 0.596/0.11 m2, the highest density was 42/0.11 m2, the positive rate of snails was 0.27%, the positive rate of mouse feces was 0.00%, and the positive rate of wild feces was 1.96%. The distribution of snails is shown

Discussion

Snail control, summarized as an “integrated control approach guided by research and scientific advances”, has played an important role in the progress made to date. The strategy of snail control should match the ecological characteristics of the habitat. The basic principle is to change the environment to make it unsuitable for the growth of snails or to make snails easy to detect for subsequent elimination (Sleigh et al., 1998). Past experience has also shown that any control plan must adhere

Conclusions

In this study, we successfully established engineering specifications for environmental modification to eliminate schistosomiasis epidemic foci in urban areas. Our findings show that environmental modification, mainly through beach and ditch remediation, can completely change the environment of Oncomelania breeding. The elimination of schistosomiasis epidemic foci in urban areas based on environmental modification and mollusciciding was demonstrated to be a better way to control snail

Authors’ contributions

KONG Shi Bo and TAN Xiao Dong designed the study, conducted the survey, drafted the manuscript and analyzed the data. DENG Zhi Qing, XIE Yao Fei, YANG Fen and ZHENG Zeng Wang conducted the survey and collated the results of the survey. KONG Shi Bo undertook the final manuscript writing. All the authors read and approved the final version of the manuscript.

Funding sources

This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.

Acknowledgments

Tan Xiaodong, Professor of School of Public Health, Wuhan University, and the staff of the Centers for Disease Prevention and Control of Jiangan District, Wuhan city, are greatly acknowledged for their help.

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