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Three Gorges Dam: Impact of Water Level Changes on the Density of Schistosome-Transmitting Snail Oncomelania hupensis in Dongting Lake Area, China.

Wu JY, Zhou YB, Chen Y, Liang S, Li LH, Zheng SB, Zhu SP, Ren GH, Song XX, Jiang QW - PLoS Negl Trop Dis (2015)

Bottom Line: There were two severe droughts that happened in 2006 and 2011, with much fewer number of flooding per year compared with other study years.The TGD influenced water levels and reduced the risk of flooding and the density of living snails in the study region.Control of S. japonica would continue to be an important task in the study area in the coming decade.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology, School of Public Health, Fudan University, Shanghai, China; Key Laboratory of Public Health Safety, Ministry of Education, Fudan University, Shanghai, China; Center for Tropical Disease Research, Fudan University, Shanghai, China.

ABSTRACT

Background: Schistosomiasis remains an important public health issue in China and worldwide. Oncomelania hupensis is the unique intermediate host of schistosoma japonicum, and its change influences the distribution of S. japonica. The Three Gorges Dam (TGD) has substantially changed the ecology and environment in the Dongting Lake region. This study investigated the impact of water level and elevation on the survival and habitat of the snails.

Methods: Data were collected for 16 bottomlands around 4 hydrological stations, which included water, density of living snails (form the Anxiang Station for Schistosomiasis Control) and elevation (from Google Earth). Based on the elevation, sixteen bottomlands were divided into 3 groups. ARIMA models were built to predict the density of living snails in different elevation areas.

Results: Before closure of TGD, 7 out of 9 years had a water level beyond the warning level at least once at Anxiang hydrological station, compared with only 3 out of 10 years after closure of TGD. There were two severe droughts that happened in 2006 and 2011, with much fewer number of flooding per year compared with other study years. Overall, there was a correlation between water level changing and density of living snails variation in all the elevations areas. The density of living snails in all elevations areas was decreasing after the TGD was built. The relationship between number of flooding per year and the density of living snails was more pronounced in the medium and high elevation areas; the density of living snails kept decreasing from 2003 to 2014. In low elevation area however, the density of living snails decreased after 2003 first and turned to increase after 2011. Our ARIMA prediction models indicated that the snails would not disappear in the Dongting Lake region in the next 7 years. In the low elevation area, the density of living snails would increase slightly, and then stabilize after the year 2017. In the medium elevation region, the change of the density of living snails would be more obvious and would increase till the year 2020. In the high elevation area, the density of living snails would remain stable after the year 2015.

Conclusion: The TGD influenced water levels and reduced the risk of flooding and the density of living snails in the study region. Based on our prediction models, the density of living snails in all elevations tends to be stabilized. Control of S. japonica would continue to be an important task in the study area in the coming decade.

No MeSH data available.


Related in: MedlinePlus

Map of sampling area and hydrological station in Anxiang county, Hunan province, People’s Republic of China.
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pntd.0003882.g001: Map of sampling area and hydrological station in Anxiang county, Hunan province, People’s Republic of China.

Mentions: This study was conducted in the 16 bottomlands near four hydrological stations in Anxiang County of the Dongting Lake region (Fig 1). These bottomlands are outside the embankment. The Dongting Lake is located at 28°30′–30°20′N and 111°40′–113°40′E in the northeastern part of Hunan Province and covers a water surface area of 2,681 km2, and plays an important role in regulating the amount of water in the Yangtze River [17]. It is a typical S. japonica endemic area with an at-risk population of about 429,000 people in marshland and lake regions [18]. Anxiang County is located in the Dongting Lake area and at the downstream of the TGD. There are 4 hydrological stations located in Anxiang County and for each hydrological station we selected 4 bottomlands as our study fields (Fig 1): 1) Guanyuan hydrological station—Qinglong, Dongbao, Nanyang and Yangshutan; 2) Zizhiju hydrological station—Yandoukou, Dongdi, Yongheyuan, Yifenju; 3) Shiguishan hydrological station—Qiangkou, Huangjiatai, Fuxing, Wuyang; and 4) Anxiang hydrological station—Yucheng, Liujiao, Zhulin, Anxiang. A total of sixteen bottomlands were divided into 3 groups according to three elevation: Low (<33m), medium (33 to 35m) and high (>35 m).


Three Gorges Dam: Impact of Water Level Changes on the Density of Schistosome-Transmitting Snail Oncomelania hupensis in Dongting Lake Area, China.

Wu JY, Zhou YB, Chen Y, Liang S, Li LH, Zheng SB, Zhu SP, Ren GH, Song XX, Jiang QW - PLoS Negl Trop Dis (2015)

Map of sampling area and hydrological station in Anxiang county, Hunan province, People’s Republic of China.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4482622&req=5

pntd.0003882.g001: Map of sampling area and hydrological station in Anxiang county, Hunan province, People’s Republic of China.
Mentions: This study was conducted in the 16 bottomlands near four hydrological stations in Anxiang County of the Dongting Lake region (Fig 1). These bottomlands are outside the embankment. The Dongting Lake is located at 28°30′–30°20′N and 111°40′–113°40′E in the northeastern part of Hunan Province and covers a water surface area of 2,681 km2, and plays an important role in regulating the amount of water in the Yangtze River [17]. It is a typical S. japonica endemic area with an at-risk population of about 429,000 people in marshland and lake regions [18]. Anxiang County is located in the Dongting Lake area and at the downstream of the TGD. There are 4 hydrological stations located in Anxiang County and for each hydrological station we selected 4 bottomlands as our study fields (Fig 1): 1) Guanyuan hydrological station—Qinglong, Dongbao, Nanyang and Yangshutan; 2) Zizhiju hydrological station—Yandoukou, Dongdi, Yongheyuan, Yifenju; 3) Shiguishan hydrological station—Qiangkou, Huangjiatai, Fuxing, Wuyang; and 4) Anxiang hydrological station—Yucheng, Liujiao, Zhulin, Anxiang. A total of sixteen bottomlands were divided into 3 groups according to three elevation: Low (<33m), medium (33 to 35m) and high (>35 m).

Bottom Line: There were two severe droughts that happened in 2006 and 2011, with much fewer number of flooding per year compared with other study years.The TGD influenced water levels and reduced the risk of flooding and the density of living snails in the study region.Control of S. japonica would continue to be an important task in the study area in the coming decade.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology, School of Public Health, Fudan University, Shanghai, China; Key Laboratory of Public Health Safety, Ministry of Education, Fudan University, Shanghai, China; Center for Tropical Disease Research, Fudan University, Shanghai, China.

ABSTRACT

Background: Schistosomiasis remains an important public health issue in China and worldwide. Oncomelania hupensis is the unique intermediate host of schistosoma japonicum, and its change influences the distribution of S. japonica. The Three Gorges Dam (TGD) has substantially changed the ecology and environment in the Dongting Lake region. This study investigated the impact of water level and elevation on the survival and habitat of the snails.

Methods: Data were collected for 16 bottomlands around 4 hydrological stations, which included water, density of living snails (form the Anxiang Station for Schistosomiasis Control) and elevation (from Google Earth). Based on the elevation, sixteen bottomlands were divided into 3 groups. ARIMA models were built to predict the density of living snails in different elevation areas.

Results: Before closure of TGD, 7 out of 9 years had a water level beyond the warning level at least once at Anxiang hydrological station, compared with only 3 out of 10 years after closure of TGD. There were two severe droughts that happened in 2006 and 2011, with much fewer number of flooding per year compared with other study years. Overall, there was a correlation between water level changing and density of living snails variation in all the elevations areas. The density of living snails in all elevations areas was decreasing after the TGD was built. The relationship between number of flooding per year and the density of living snails was more pronounced in the medium and high elevation areas; the density of living snails kept decreasing from 2003 to 2014. In low elevation area however, the density of living snails decreased after 2003 first and turned to increase after 2011. Our ARIMA prediction models indicated that the snails would not disappear in the Dongting Lake region in the next 7 years. In the low elevation area, the density of living snails would increase slightly, and then stabilize after the year 2017. In the medium elevation region, the change of the density of living snails would be more obvious and would increase till the year 2020. In the high elevation area, the density of living snails would remain stable after the year 2015.

Conclusion: The TGD influenced water levels and reduced the risk of flooding and the density of living snails in the study region. Based on our prediction models, the density of living snails in all elevations tends to be stabilized. Control of S. japonica would continue to be an important task in the study area in the coming decade.

No MeSH data available.


Related in: MedlinePlus