What does snail transfer mean?

It is necessary to be alert that the South-to-North Water Transfer Project will become the only way for schistosomiasis to move northward.

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20051October 10 China News Network

Public trust. Com 65438+ 10/0, 1958, Mao Zedong wrote a famous poem "Send the plague god", and the word "plague god" became synonymous with schistosomiasis. Time flies, in the eyes of many people, especially northerners, schistosomiasis, known as "abdominal disease", seems to have become a distant past. But in fact, this "plague god" has never stopped raging. Now, it is likely to spread northward through the South-to-North Water Transfer Project.

According to the Science Times, experience at home and abroad shows that the construction of large-scale water conservancy projects will lead to the spread of snails and the outbreak of schistosomiasis. Li Shuqiang, a researcher at the Institute of Zoology, Chinese Academy of Sciences, said in an interview recently that it is very important to strengthen the research on whether the South-to-North Water Transfer Project will cause schistosomiasis to spread northward and its local problems in northern China, because the water intake of the east route of the South-to-North Water Transfer Project is directly an endemic area of schistosomiasis, and the Hu Si area in Hubei Province where the middle route project passes is also an endemic area of schistosomiasis.

Li Shuqiang said that at present, there is a very serious schistosomiasis epidemic in the Yangtze River basin and its south/409 cities, districts and counties in Kloc-0/2 provinces, municipalities and autonomous regions, and the spread of the epidemic is mainly related to the spread of Oncomelania hupensis, the only intermediate host of schistosomiasis.

Experts believe that whether the epidemic situation of schistosomiasis in southern China spreads to the north and causes harm locally in the north is mainly affected by two factors:

First, is it possible for infected snails to migrate northward with the current and survive for a short time? A large number of research data show that the spread of Oncomelania hupensis along the Yangtze River basin in China is very serious-Oncomelania hupensis can drift along the river for as long as 168 km, and it can drift over 100 km during flood peak period. Oncomelania hupensis can float on the water surface and spread northward with the water, but infectious Oncomelania hupensis can also spread with people and other organisms. Because Oncomelania hupensis has strong vitality, it may survive for several days in the north (such as Beijing) in summer.

The second factor is whether snails can reproduce after spreading northward. Temperature is considered to be one of the main factors limiting the distribution range of Oncomelania hupensis. In the past 100 years, the global temperature has increased by 0.4℃ ~ 0.6℃. It is predicted that the global temperature will rise by 1℃ ~ 3.5℃ due to the greenhouse effect in this century, and global warming will help snails move northward. At present, the northern boundary of schistosomiasis endemic areas in China is also the northern boundary of snail distribution, which is located at 3315' north latitude, while the northern boundary of schistosomiasis endemic areas in the world is 36 north latitude. Therefore, Hongze Lake and Chaohu Lake, the fourth and fifth largest freshwater lakes in China, have the potential threat of becoming endemic areas from non-endemic areas of schistosomiasis, and the possibility of long-term spread to Shandong and Henan also exists.

Experts pointed out that even areas that are not suitable for snail breeding at present, such as some northern provinces, can still be attacked by schistosomiasis in summer, eventually leading to human or animal infection with schistosomiasis. In addition, after the completion of the South-to-North Water Diversion Project, due to the long-term artificial diversion of a large number of rivers to the north, some snails may gradually evolve into geographical populations adapted to the natural environment in the north through natural selection.