Objective To investigate the changes and seasonal fluctuations in the species composition and densities of mosquitoes in Three Gorges Reservoir Area in Yichang, Hubei province, China. Methods Mosquitoes were captured by electric mosquito-catching trap at fixed times and places and were then identified and counted. Results In the early stage of the construction of Three Gorges Reservoir Area in Yichang, the dominant species of mosquitoes in human houses and livestock pens were Culex pipiens quinquefasciatus, Armigeres subalbatus, Cx. pipiens pallens, and Anopheles sinensis. The dominant species, however, has been Ar. subalbatus in human houses since 2005 and in livestock pens since 2007. The adult mosquito density was significantly lower in human houses than in livestock pens. The seasonal fluctuation in adult mosquito density was in a bimodal pattern, with density peaks in the first ten-days period of June and the first ten-days period of August. Conclusion With the environmental changes in the Three Gorges Reservoir Area in Yichang, the density and species composition of mosquitoes vary. Mosquito monitoring should be strengthened to provide the basis for decision-making basis for effective prevention and control of vector-borne diseases.

Objective　The vectors variation trends before and after impoundment of the Three Gorges Reservoir in Yichang were monitored and analyzed for timely implementation of the countermeasures. Methods　The indoor and outdoor rodent density, mosquito density in residential houses and livestock pens, and species composition of rodents and mosquitoes were determined using the night trap method and the labor hour method. Results　No significant changes were observed in the rodent density after impoundment of the Three Gorges Reservoir in Yichang (t＝0.52, P＞0.05). The annual variation of the rodent density constituted a primary decline followed by an increase. As for the small mammal species composition, the indoor and outdoor dominant species before impoundment were Rattus norvegicus and those of the genus Sorex, accounting for 71.07% and 42.11%, respectively. The dominant species after impoundment, indoor and outdoor, were both R. tanezumi, accounting for 41.67% and 42.86%, respectively. The mosquito density in residential houses did not change significantly after impoundment (t＝1.29, P＞0.05), whereas the mosquito density in livestock pens increased significantly (t＝5.01, P＜0.01). In regard to the mosquito species composition, Anopheles sinensis and Culex pipiens pallens were the dominant species before impoundment in residential houses and livestock pens, respectively, accounting for 38.50% and 34.65%; Armigeres subalbatus and An. sinensis were the dominant species after impoundment, accounting for 37.21% and 23.18%, respectively. Conclusion　The environmental changes due to impoundment of the Three Gorges Reservoir in Yichang had led to the alteration in rodent species composition, in addition to significantly increased mosquito density in livestock pens and altered mosquito species composition. It is suggested that vector  monitoring  should  be  strengthened  to  provide  the  decision?making  basis  for  effective  prevention  and  control  of  the occurrence and prevalence of vector?borne diseases.

　　【Abstract】　Objective　Know the dynamic change of mosquito population constitution and its density and its seasonal fluctuation in Three Gorges Reservoir area. Methods　The mosquitoes were captured by direct current electric mosquito-catching trap at the fixed time and places, and then identified and counted. Results　The dominant species of mosquitoes were Armigeres subalbatus, Culex pipiens quinqusfasciatus, Anopheles sinensis, Cx.tritaeniorhynchus and Cx.pipiens pallens in the Three Gorges Reservoir area. The density of mosquito in room was higher than outside. Conclusion　The density of mosquito tended to decline from 1997 to 2007, and mosquito monitoring should be strengthened.

Objective To provide the measures for disease control and prevention through the analysis of leptospirosis in Yichang from 1997 to 2006. Methods The descriptive epidemiological methods were used to analyze the epidemic situation of leptospirosis and to understand the epidemiological characters. Results There were 526 cases of leptospirosis, 18 of which were died and the annual incidence was 1.32/lakh in Yichang from 1997 to 2006. The high-risk group was the males aged from 20 to 50 years old, especially the peasants. And the peak periods were August and September, while there were different incidence in different zones and the highest was Zhijiang. Conclusion The incidence trend of leptospirosis was generally downward in Yichang from 1997 to 2006. However, it should continually strengthen surveillance to avoid outbreak of the rain-water-type and flood-type leptospirosis caused by bad weather. And it was important for the control and prevention of leptospirosis to enforce deratization and enhance the susceptible herd immunity by vaccination.