Dynamics of Rodent and Rodent-borne Disease during Construction of the Three Gorges Reservoir from 1997 to 2012.

OBJECTIVE: To investigate the impact of impoundment and active public health interventions on rodent populations and rodent-borne diseases in the Three Gorges reservoir region from 1997 to 2012. METHODS: Surveillance data from 1997 to 2012 were extracted from the Public Health Surveillance System of The Three Gorges established in 1997. Temporal changes in the incidences of hemorrhagic fever with renal syndrome (HFRS) and leptospirosis, rodent density, pathogen-carrying rates, and their correlations were analyzed. RESULTS: The average indoor and outdoor rodent densities decreased overall from 1997 to 2012. The average densities decreased by 47.72% (from 4.38% to 2.29%) and 39.68% (from 4.41% to 2.66%), respectively, after impoundment (2003-2012) compared with before impoundment (1997-2002). The average annual incidence rates of HFRS and leptospirosis were 0.29/100,000 and 0.52/100,000, respectively, and decreased by 85.74% (from 0.68/100,000 to 0.10/100,000) and 95.73% (from 1.47/100,000 to 0.065/100,000), respectively, after impoundment compared with before impoundment. Incidences of HFRS and leptospirosis appear to be positively correlated with rodent density in the reservoir area. CONCLUSION: This study demonstrated that rodent density and incidences of rodent-borne diseases decreased and were maintained at low levels during construction of the Three Gorges dam. Measures that reduce rodent population densities could be effective in controlling rodent-borne diseases during large-scale hydraulic engineering construction.

[Effect of comprehensive control and prevention for chronic disease in demonstration plot of Chongqing].

OBJECTIVE: To evaluate the effect of comprehensive control and prevention for chronic diseases in demonstration plot of Chongqing. METHODS: Residents were enrolled through multi-stage stratified random sampling method from 17 districts or counties which had successfully established demonstration plots and 21 districts or counties which had not established demonstration plots (non-demonstration plot for short) yet on May, 2012. Questionnaire was designed to survey awareness of health knowledge, health behaviors and utilization of health supportive tools. The results were analyzed by SPSS 15.0 software. RESULTS: We investigated 15 108 residents, 6156 of which were in demonstration plot and others (8951) were not. The findings revealed the percentage of the people who were aware the national action of health lifestyle in demonstration plot and in non-demonstration plot were 44.4% (2734/6157) and 40.2% (3598/8951), respectively, and the awareness of the hypertension risk of too much sodium were 72.4% (4458/6156) and 67.5% (6042/8951), respectively, and the awareness of the cardinal vascular disease (CVD) risk of obesity and overweight were 77.2% (4753/6157) and 69.6% (6230/8951), respectively. About the residents' health behaviors in demonstration plot and in non-demonstration plot, the utilization rates of salt restriction scoop or pot were 23.5% (1447/6157) and 17.9% (1602/8951), and the utilization rates of oil restriction pot were 16.7% (1028/6157) and 11.8% (1064/8951), respectively. Totally, 33 of the 37 indexes were shown higher in demonstration plot than that in non-demonstration plot (P < 0.05). CONCLUSION: The chronic diseases comprehensive control and prevention in demonstration plot was more effective, and the remarkable improvement of health knowledge and behaviors level had been achieved in demonstration plot.

[Surveillance on the health status regarding vector-borne disease among people living in the Three Gorges Reservoir Area (1997 - 2009)].

OBJECTIVE: To evaluate the impact on the health status of population in the area where the 'Three Gorges Reservoir Water Storage Project' had been operated and to provide references for the development of related disease control strategies. METHODS: In the Three Gorges Reservoir Area, 17 towns/streets in nine counties were chosen as surveillance points. Data on surveillance program would include infectious diseases, birth, death, biological agents etc. METHODS: related to time and spatial analysis and the comparison on pre- and post-water storage were used to analyze and describe the long-term changing trend of meteorological index, distribution of biological agent and diseases, and human health status. Relationships between number of infectious diseases and media biological density and meteorological parameters were also analyzed. RESULTS: When the water storage program came into being in 2003, the indoor (2.22%) and outdoor (2.76%) densities of rats were significantly lower than pre-water storage period (indoor 4.38% vs. outdoor 4.43%) and the annual average density of mosquito (35.09 mosquitoes per room and per hour) was also lower than before (54.24 mosquitoes per room and per hour). The incidence rates of encephalitis B, malaria, leptospirosis, and hemorrhagic fever had reduces 22.88%, 84.85%, 95.03% and 81.82% than before. The incidence rates of malaria, leptospirosis, and hemorrhagic fever were all below 0.4/100 000 and the incidence of encephalitis B was below 2/100 000. The average infant mortality was 11.83‰. The annual infant mortalities, after adjusted by missing report numbers, were between 13.07‰ and 23.88‰ which were lower than the national annual average level. The thirteen year standard mortalities were 3.77‰ - 5.12‰, with the total rate lower than the national average level in the same years. CONCLUSION: In 2003, the incidence rates of malaria, encephalitis B, leptospirosis, epidemic hemorrhagic fever kept going down in the surveillance sites in the Three Gorges Reservoir Area, and the overall population's health status was well enough to show that there was no negative impact on the health status of population living in the area after the water storage project was inplemented.

[Study on the characteristics of major mosquito-borne infectious diseases in Three Gorges Reservoir Area from 1997 to 2008].

OBJECTIVE: Characteristics and tendency of mosquito and major mosquito-borne diseases (including epidemic encephalitis B and malaria) were analyzed in the Three Gorges Reservoir Area from 1997 to 2008. METHODS: Information on surveillance data related to mosquito-borne infectious diseases and on mosquito density and category, from 1997 to 2008 was collected from Health Surveillance System in Three Gorges Reservoir Area. Data regarding meteorological factors and construction of Three Gorges Reservoir was also collected. Pearson and Poisson models were used. RESULTS: From 1997 to 2008, in the Three Gorges Reservoir Area, the incidence rates of epidemic encephalitis B and malaria were decreasing. Positive correlations were shown between indoor and outdoor mosquito density as well with temperature with coefficient as 0.281 and 0.355 respectively. Correlations of mosquito-borne diseases with indoor and outdoor mosquito density were positive, with correlation coefficient as 0.340 and 0.328 respectively. CONCLUSION: There seemed lack of evidence to prove that negative influences had occurred on the incidence of mosquito-borne infectious diseases or the mosquito density after the Three Gorges Reservoir water storage came into being in 2003, however, long-time surveillance program needs to be carried out to gather information on this issue.

[Study on the health status and affecting factors among people living in the surveillance sites of three Gorges Reservoir Areas, in 2007].

OBJECTIVE: To understand the health status and potential impact resulted in the second stage of Three Gorges Reservoir Areas sluicing. METHODS: Data were collected on deaths, prevalence rates of infectious and endemic diseases, as well as on vector surveillance through the project entitled 'Three Gorges Population Health Survey System'. RESULTS: The main causes of death in the population living in the Three Gorges Reservoir Areas would include: circulatory system diseases, tumors, respiratory system diseases, injuries/poison and digestive system diseases. The number of deaths caused by the above said five kind of diseases accounted for 90.94% of the total number of deaths. The prevalence rates on Water-born diseases related to the sluicing of reservoir and zoonosis-borne diseases related to the changes of vectors were still low. The indoor and outdoor densities of rodents were 3.11% and 3.16%, both were higher than that in 2006 but lower than the average numbers in the five years prior to the sluicing. The constituent ratio of Apodemus agrarius had constantly risen since 2006. The density of mosquitoes found in livestock barns and human households was higher than that in 2006 but lower than the average number of the five-year studies prior to the sluicing. CONCLUSION: Environment change after the sluicing of the Three Gorges Reservoir Areas did not seem to have obvious impact on the health status of the people living in the areas. However, to strengthen the surveillance on the biological features of the vectors which might have related to the transmission of diseases would be highly recommended.

[Surveillance on the dynamics of leptospirosis epidemics in the Chongqing Section of the Three Gorges dam area].

OBJECTIVE: To analyze the changes of leptospirosis epidemic characteristics before and after the Phase 2 'reservoir store water project' in Chongqing section of the Three Gorges dam area and to provide prevention, control and intervention measures to prevent the spread of leptospirosis from infectious focus to the Three Gorges dam area and downstream region of Changjiang River. METHODS: Changshou district and Fengdu county were selected as surveillance sites. We monitored the source of infection through examining the serum antibody of patients, healthy groups together with farm cattle measured by micro agglutination test (MAT). RESULT: Sporadic cases were reported before and after the storage of water in the reservoir. There was no significant difference found between mouse density before and after the Phase 2 reservoir project (chi2 = 1.00, P > 0.05). The main species of rat were Sewer rat before and Insectivorea after the storage of water. The germ-carrying rate of rats was 1.72% (10/583) and positive carrying rate of rats was 16.51% (18/109) when using PCR. Results showed a significant difference when comparing it to culture method (chi2 = 51.80, P < 0.01). Positive rate of leoptopirosis appeared in the serum of patients was 73.33% (33/45) with the major serum group as the Australia group. The rate of infection among the healthy group was 26.84% (233/868). There was significant difference seen between the serum antibody positive rate of epidemic prophase (23.85%) and epidemic anaphase (29.86%) of the healthy group (chi2 = 3.99, P < 0.05). The GMRT of ox serum antibody of leoptopirosis was 29.97 with Bailen group as the predominant microbial population. CONCLUSION: There was no epidemics of leptopirosis occurred in the Three Gorges dam area. There was no significant difference between mouse density before and after the storage of water in the reservoir. However, the major species of rats had a change. The natural infection level of people living in the dam area was low, but there existed potential of leoptopirosis outbreak.

[Estimation on the level of birth and death rates of population in the three gorges area by means of capture-mark-recapture method].

OBJECTIVE: To evaluate quality of surveillance and emendate rates of birth and death of population of the Three Gorges area. METHODS: Data on the two samples collected were designed based on principle of capture-recapture method. An investigation of missing report of birth and death was conducted in 7061 families selected through stratified random sampling method. We collected and registered the data of birth and death in every family investigated and checked with correlative records reported in disease surveillance system of the Three Gorges area. The missing report rates and the 95% confidence intervals of birth rate and death rate were calculated. RESULTS: The underreporting rates of birth and death were 13.91% and 15.60% and death of infant was 33.33%. The emended birth rate was 8.92 per thousandth and the 95% confidence interval of birth rate was 8.38 per thousandth-9.45 per thousandth. The emended report rate of death was 6.88 per thousandth and the collectivity 95% confidence interval was 6.37%-7.38 per thousandth. CONCLUSION: Results showed that the quality of birth and death in the disease surveillance reporting system of Three Gorges area was competent to the quality level of the standard set for national disease surveillance system. The birth and death rates of population in the Three Gorges area were under 10.00 per thousandth.