| Plague is a strong infectious disease caused by Yersinia pestis, also is a natural infectious disease, which is one of the category A infectious disease in China. Plague can be spread independently in rodents, under certain conditions, can be transmitted to humans and result in human plague prevalence. Since the founding of People's Republic of China, we have achieved a certain success in plague prevention and control work and it has been effectively controlled. With new founding foci and increasing epidemic focus counties, however, the plague has rebounded significantly since 1990 s. Until now, there are 12 kinds of natural foci and 21 types of Yersinia pestis are found in China.Objective: To described the plague distribution in Microtus fuscus foci from 2001 to 2015 and to investigate the epidemic situation and the change trend of the plague as well as to study the correlation between the animal plague and its influencing factors; The natural and human influencing factors for plague prevalence are studied in the thesis so as to provide scientific basis for plague control and prevention.Methods: Combining with the laboratory test results, the surveillance data of plague in Microtus fuscus foci from 2001 to 2015 were analyzed, and prevalence law of distribution of the plague was described. EXCEL was employed for data processing, SPSS statistical software for data analysis, Mapinfo thematic map production was performed. Correlation analysis and multiple linear regression as statistical analysis method in the thesis.Results: The primary host of Microtus fuscus foci is Microtus fuscus, and the main mediums are Citellophilus sparsilis and Amphipsylla tuta tuta. The focus is mainly distributed in Shiqu Connty of Sichuan Province and Chengduo County of Qinghai Province; these areas are 21000 square kilometers.From 2001 to 2015, there were 68.37hm2 plots had been investigated,15432 Microtus fuscus were captured with the average density of 225.71/hm2; 33620 mousetraps were placed, 506 rodents were captured with capture rate of 1.51%.A total of 15432 Microtus fuscus were examined, 6812 were infected with fleas with rate of 41.48%; 13959 fleas were examined with index rate of 0.90. A total of 399 nests of Microtus fuscush had been digged with flea rate of 100%; 22261 fleas were captured with average index of 55.79.A total of 15505 host animals had been tested in the etiological test, 94 strains of the plague were isolated with positive detection rate of 0.61%; 1928 groups of vector insects were tested and 12 strains were Isolated.The Animal plague situation in Microtus fuscus foci from 2001 to 2015 was analyzed as follows, the animal plague mainly occurred in May, June and July. 3847 animal serum was tested in serological tests, 202 positive samples were detected with positive detection rate of 5.25%. The largest proportion of serologic titer in Microtus fuscus foci is between 1:80 and 1:640, and the highest serological titer was up to 1:10240.There was a positive correlation between the positive rate of animal serum and the density of rats. There was no simple linear relationship between rodent density, rodents' parasitic flea rate, rodents' parasitic flea index, flea positive rate and animal serum positive rate.Conclusion: The animal plague situation of Microtus fuscus foci is occurred frequently and the foci is in active stage that mainly distributed is in Shiqu County,no human plague outbreak is reported.The positive rate of animal serum increased with the increase of the density of rats,there is not a simple linear relationship between the animal epidemic and the factors of the foci. |
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