Assessing The Impact Of Three Gorges Project On The Dynamics Of Leptospirosis In Three Gorges Area

Objective 1. We want to multi-analysis the current prevalence conditions and the dynamic trend of Leptospirosis in the Three Gorges Area and assess the impact of the Three Gorge project on it systematically, so that we can provide basical references for decision-makers of the relevant departments. What's more, we dedicate to study the methodology for evaluating the impacts of major projects on focal diseases. 2. We try to propose a concept of"Biological security of eco-environment"as a new strategy to prevent and control infectious diseases. That's to say, we advise starting with the eco-environment to eradicate the increasingly serious burden of infectious diseases.Methods 1. We sampled four villages as field studying areas from Zigui and Yiling countries in Yichang, and then detected the rodent population with mouse traps. The kidneys of each captured rodent were inoculated in Korthof medium for Leptospirosis culturing. 2. A seroepidemiological survey was conducted to examine the infected rate of Leptospirosis in the common population of these areas. 3. Through the published documents, we collected the Leptospirosis incidence and the rodent dynamic information in the Three Gorge area, and extracted the information about weather, agriculture, and etc from the environmental and ecological monitoring bulletins of the Three Gorges area between 1997 and 2007. 4. We use Excel 2003 to establish the data sets and draw the graph tables, and completed the statistical analysis with a popular software named SAS 8.1.Result 1. From 1997 to 2005, the rodent population densities there fluctuated between 2.81% and 6.15%, the changing curve looks like an irregular"W". Correlation analysis showed that there was a positive correlation between the rodent densities and the changes of the crop area in the Three Gorges region. The field investigation in 2006 and 2007 suggested that the rodent density in the dam area was increasing, and the density in residence was significantly higher than that in the fields. Of all the captured rodents in the dam area, Rattus flavipectus was the dominant species, accounting for 29.58%. The species constitution was different between the indoor rodents and the outdoor ones. Indoor dominant species were Rattus flavipectus and Mus musculus. Outdoor dominant species were APodmus agrarlus and Rattus norregicus. And there was a cross-migration phenomenon between indoor and outdoor rats. 2. The infected rate of Leptospirosis in the common population of the dam area was 16.91%, and it had an ascending trend with the age increasing. The infected rates in the males and females were 16.39% and 17.35% respectively, and there was no significant difference between them. The infected persons were mainly farmers, whose seroprevalence rate was 29.61%. 3. The positive rate of rodent renals'Leptospirosis culturing was 18.30% in the dam area. Of all the species, APodemus had the highest positive rate as to 30.56%. 4. From 1996 to 2005, the Leptospirosis incidence rates in the Three Gorges area were at relatively low levels, fluctuating between 0/100000 and 2.588/100000. The rates increased lightly in 1998 and 2000 respectively, and decreased in the remaining years. From 2003 to 2005, no cases were reported. The incidence rate was markably positive correlation with the outdoor rodent density, while negative correlation with the rural per capita income.Conclusion 1. The Leptospirosis incidence is still at a low level at present in the Three Gorges area. During the period of water storing, however, the potential risk of the outbreak or epidemic still exists. In the long term, Three Gorges project will be beneficial to prevent and control Leptospirosis of this area. The development of tourism might lead to the importation of large susceptible population, and the increasingly flowing of people and goods may drive the alternation of the predominant Leptospire spp in this area. Therefore, it still needs to strengthen monitoring and managing. When the water level reaches 175m, the emergence of a riparian zone will promote the forming of a wetland ecological community, its impact on the Leptospirosis prevalence deserves further concern. 2. To any large-scale project, we should start with the changes of ecological and social environment, demographic characteristics and population behaviors to evaluate its impacts on focal diseases qualitatively and quantitatively. In the process of assessing, the most crucial and difficult thing is to establish a prewarning indicator system. 3. Through studying and assessing biological security of eco-environment, we can interfere with the formation of pathogens, or cut their way into the crowd. In other words, we can put the starting point forward of infectious diseases preventing to avoid new infectious diseases occurring and developing in human beings, so that we can virtually eliminate or ease the burden of infectious diseases. On the other hand, biological security could be an integral part of the ecological security. While thinking about how to protect ecosystems, we should also attach importance to the protection of our own health, thereby truly achieved harmony development between human and nature.