Epidemiological analysis of Plague in Dehong Dai and Jingpo Autonomous Prefecture of Yunnan province, 1950-2019

Abstract

Objective: To analyze the epidemic situation and influencing factors of plague in Dehong Dai and Jingpo Autonomous prefectures (Dehong) from 1950 to 2019, for the improvement of strategies on prevention and control of the disease. Methods: The epidemic situation and surveillance data of animal and human plague in Dehong prefecture from 1950 to 2019 were collected and analyzed by descriptive epidemiological methods. Multiple linear regression equations were established by SPSS 20.0 software to analyze the relationship between plague among animals and rat density and flea index, as well as the relationship between human plague and plague among animals. Results: In Dehong prefecture, plague experienced a phenomenon of epidemic-resting-epidemic-resting cycle, between 1950 and 2019. During this period, 614 epidemic spots were identified in 36 townships of five counties/cities,. Human plague had been prevalent for 15 years, with 1 153 human cases and 379 deaths involved. Between 1982 and 2019, 261 319 rodents were captured, of which Rattus flavipectus accounted for 70.95%(185 421/261 319). A total of 70 124 fleas were seized with 76.65%(53 752/70 124), xenopsylla cheopis as fleas. The index of fleas and free fleas were 0.57 and 0.22 respectively. A total of 1 577 strains of Yersinia pestis were isolated from 285 091 animal specimens and 418 strains of Yersinia pestis were isolated from 60 119 groups of fleas, with 255 F1 antibody positive samples were detected from 64 157 sera samples. Neither Yersinia pestis nor the outbreak of plague had been noticed since 2008. Correlations between both animal plagues and rat density, as well as human plague and animals plague were noticed from the regression analysis. Conclusions: The epidemics of plague were with long-term and stable nature, in Dehong prefecture. Affected by many factors, plague seemed in a resting period currently. However, we should be reminded that the fact that outbreak of plague may revive at some uncertaint point. Hence in order to prevent human plague, strategies as careful surveillance programs on animals, need to be strenthened.