Objective To investigate the barrier effect of rivers on the spread of rodent plague. Methods The data of the rodent plague foci in Dehong autonomous prefecture of Yunnan province, China, from January 1982 to December 2007 were collected. The numbers of townships and plague foci with rodent plague were recorded in each county (city) and in each of the three regions divided by the Daying River and Longchuan River (national borders-Daying River, Daying River- Longchuan River, and Longchuan River-prefecture borders) in each year. The epidemic intensity values of five counties (cities) and three regions were calculated according to the entropy index and adjusted for area size. The difference in adjusted epidemic intensity between the five counties (cities) or the three regions were analyzed using the Kruskal-Wallis H test. Results During 1982-2007, in Yingjiang, Lianghe, Longchuan, Ruili, and Mangshi, rodent plague was epidemic for 16, 11, 19, 11, and 10 years, respectively, and the numbers of plague foci were 159, 96, 93, 76, and 35, respectively. There was no significant difference in the overall distribution of adjusted epidemic intensity between the five counties ( H=8.277, P=0.082). In the three regions (national borders-Daying River, Daying River-Longchuan River, and Longchuan River-prefecture borders), plague was epidemic for 16, 25, and 10 years, respectively, and the numbers of plague foci were 103, 321, and 35, respectively. There was a significant difference in the overall distribution of adjusted epidemic intensity between the three regions ( H=19.738, P=0.000), and significant differences were also observed between the region from Longchuan River to Daying River and the region from national borders to Daying River or the region from Longchuan River to prefecture borders ( χ ²=18.423, P=0.003; χ ²=26.692, P=0.000). Conclusion Rivers may have a barrier effect on the spread of rodent plague in Dehong prefecture, which may be related to the effects of rivers on the geographical distribution of Yersinia pestis and the community, population and distribution of the host and vector fleas of Y. pestis.

Objective To explore the feasibility using information entropy formula to measure the epidemic intensity of enzootic plague. Methods The epidemic intensity formula named I _a for enzootic plague based on the information entropy formula was proposed, and used to calculate the epidemic intensity of hypothetical data in 8 epidemic foci (the number of township ≥ 8). The spearman correlation coefficient of the epidemic intensity between Yingjiang and Longchuan counties during 1982-2005 was calculated. Results The epidemic intensity of the hypothetical data showed that the epidemic intensity was the smallest (0.288) when 8 foci were concentrated in 1 townships, while the largest (2.079) when 8 townships each had 1 epidemic focus; with the same foci, the more townships involved in the epidemic, the greater the prevalence intensity. The largest epidemic intensity of Yingjiang (2.107) and Longchuan (1.642) were discovered in 1995 and 1990 respectively; the biggest epidemic intensity of Yingjiang appeared in 1995 (I _a=2.107), rather than in 1993 (I _a=1.885) with the most epidemic foci. The correlation coefficient of epidemic intensity in two counties was 0.301 ( P=0.150), which showed that there was no statistical correlation. Conclusion The formula verified by simulated and actual data is proved to be able to describe the features of complexity and hierarchical structure of plague epidemic, and make possible the comparisons of epidemic intensity temporally and spatially.

【Abstract】 Objective To deeply know the role of the reporting of dead rodents in the monitering and control of commensal rodent plague and its cooperation with linking surveillance method. Methods  （1）To compare and analyze the function of dead rodents reporting and three plague?risk indicators reporting on the timely finding of the plague in rodents. （2）To analyze the relationship between dead rodents reporting and linking surveillance method and study the function of the latter. Results （1） The reporting of dead rodents contributes to, and other two plague?risk indicators reporting has no relation to the detection of commensal rodent plague among rodents.（2）The two HD techniques in monitoring and control system of commensal rodent plague are dead rodents reporting and linking surveillance method, of which, the former is mainly in charge of the detection of the plague among rodents in time, and the latter has two roles, namely both decreasing and founding the epidemic foci among rodents, especially in decreasing them. Conclusion The emphasis should be put on the popularization of 2HD technique in order to detect and control rodent plague in time in the monitoring and control of commensal rodent plague, and at the same time,  the reporting of three plague?risk indicator should be understood and treated correctly.

Objective To know deeply the incidence mechanism of commensal rodent plague and scientifically work out or choose appropriate surveillance and control measures.Methods The transmission route from rodents to humans of commensal rodent plague was expressed by mathematical language to show up the inherent relations among the decisive factors,and its relevant monitoring methods were analyzed and compared.Results(1)An incidence mode function of the plague was derived.(2) The linking surveillance method was more effective than the parallel surveillance method,and the former was more accordant with the epidemiology principles,the statistics requirements and the "benefit-cost ratio" requirement because of its smaller workload.Conclusion(1)The incidence mode function on commensal rodent plague disclosed the inherent relations among the decisive factors of the disease,and had the important guide function and wide application prospects to its prevention and control.(2)The linking surveillance method should be suited to the surveillance of plague compared to the parallel surveillance method.

Objective The paper reported the results of study on the toxiticy of cyhalothrin to Xenospylly cheopis in laboratory.Methods The residual smearing method was used.Results(1) The KT ₅₀ was getting shorter with the concentration gradually creasing,and the death rates of 24 h were getting higher.(2) When the concentration of cyhalothrin were 12.50 mg/L,25.00 mg/L,50.00 mg/L and 100.00 mg/L,the KT ₅₀<6 minutes,and the knock down rates of 11 minutes >(63.0%),the death rates of 24 h>84.0%.(3) When the concentration of cyhalothrin were 50.00 mg/L and 100.00 mg/L,the shoot down rates of 30 minutes in 450 days were 100% and the death rates of 24 h in 450 days >93.0%.Conclusion The toxicticy of cyhalothrin to Xenospylly cheopis is very good and cyhalothrin can be used to control the plague in field.

Objective To study the main way of discovering commensal rodent plague foci amid host rodents in Yunnan province in 1999-2004. Methods The proportion of the foci detected with trapped rodents was compared with that of the self-dead rodents,and the self-dead rodent reporting rates were compared of different places and different years,in which different numbers of human plague cases occurred in Yunnan province in 1999-2004. Results Of all the foci those detected with self-dead rodent test reach 89.6%,whereas those detected with trapped rodent test only account for 10.4%. The self-dead rodent reporting rates in the counties or years with more human plague cases were significantly lower than those with less human plague cases. Conclusion The foci of rodent plague were found out mainly by self-dead rodent test in Yunnan province in 1999-2004,and self-dead rodent reporting was the main way to detect the foci.