The Three Gorges Dam: Does the Flooding Time Determine the Distribution of Schistosome-Transmitting Snails in the Middle and Lower Reaches of the Yangtze River, China?

Abstract

Background: Schistosomiasis is one of the most devastating tropical diseases in the world. Oncomelania hupensis is the only intermediate host of Schistosoma japonicum, and its growth and development are sensitive to environmental factors. The Three Gorges Dam has substantially altered the water level in the Yangtze River. This study focused on the impact of the flooding time on the occurrence of Oncomelania snails in Hunan Province, China. Methods: The data regarding Oncomelania snails were collected from the Schistosomiasis Atlas of the People’s Republic of China. Air temperature, hours of daylight and relative humidity from 1995 to 2002 were collected from the China Meteorological Data Sharing Service System. The data for rainfall and days inundated with water were collected from the Hunan flood control information system and hydrological stations in Hunan Province. A generalized additive model was used to estimate the impact of these factors on the presence or absence of snails. Results: The number of days inundated with water in the areas with snails ranged from 56 to 212 days. However, 82 percent of the areas without snails were inundated with water less than 60 days. The lowest air temperature in a year in the areas without snails ranges from −2.88 °C to −2.10 °C, and the range was from −2.88 °C to −2.34 °C for areas with snails. Annual rainfall in the areas with snails ranged from 989 to 1565 mm, and the range was from 1230 mm to 1647 mm for the areas without snails. The results from the generalized additive model showed that the number of days inundated with water, lowest air temperature in a year, annual rainfall, days of daily rainfall greater than 0.1 mm, and hours of daylight were the factors that significantly affect the occurrence of snails in Hunan Province, China. Conclusions: The number of days inundated with water may be a key factor determining the geographical distribution of Oncomelania snails in Hunan Province and the favorable number of days inundated with water for the survival of snails ranges from about 2 to 7 months.

Analysis of CT characteristics in the diagnosis of Schistosoma japonicum associated appendicitis with clinical and pathological correlation: a diagnostic accuracy study

“…It is also considered as the second most socioeconomically devastating condition after malaria by the World Health organization because of its high prevalence in Africa and the far east causing considerable mortality and morbidity [2,3]. Especially in China, S. japonicum has reached a criterion of elimination, as well as, transmission interruption statuses with greater efforts [4], yet it remains a major health problem in the endemic villages of many provinces connected along Yellow river and Yangtze-Jiang basins [5,6]. Despite the transmission control status, the focal transmission of S. japonicum is still vastly prevalent due to the risk of an epidemic rebound in autonomous regions of Yunnan Province especially like Dali, Lijiang, Chuxiong, and Honge city minorities.…”

Field Evaluation of a Loop-Mediated Isothermal Amplification (LAMP) Platform for the Detection of <em>Schistosoma japonicum </em>Infection in<em> Oncomelania hupemsis </em>Snails

“…This could be counteracted by using a higher number of snails in the pool and increasing the time of amplification for the test but, on the other hand, the risk for false positives would then rise. This work shows that already a dilution factor of 1/50 accelerates the areal testing considerably as the snails tested can now come from a 50 times larger area than traditionally used, something that could be a practical value already now [24]. Importantly, we are already in a situation where More investigation might provide the needed room for improvement.…”

Temporal transcriptome change of Oncomelania hupensis revealed by Schistosoma japonicum invasion

“…It is transmitted by snails infected with worms of the trematode genus Schistosoma. Oncomelania hupensis (Gastropoda: Rissooidea), mainly distributed in China's Yangtze river basin and its south, is the only intermediate host of Schistosoma japonicum, which plays a key role in the transmission of schistosomiasis in China [2,3]. The number of Schistosomiasis patients and the burden of the disease have dramatically reduced since the establishment of People's Republic of China (P.R.C), together with the national schistosomiasis control strategy shift from the morbidity control strategy to an integrated strategy in 2004 [4][5][6].…”