ABSTRACT
Objective To investigate rickettsiae infection from host animals and vector arthropods in some areas of Yunnan Province. Methods Rat clip and cage traps were used to capture mice. Chiggers from body surface of mice and ticks from body surface of farm cattle were collected. DNAs were extracted from mice spleens, chiggers and ticks. Rickettsiae groEL segment were amplified by nested-polymerase chain reaction (nPCR), sequenced to analyze the homology with other known sequences. Results A total of 410 samples were collected for rickettsiae groEL segment detection with nPCR and 19 samples (4.63%) showed positive for rickettsiae groEL segment . Among them, 2.68%(11/410)were positive for Orientia tsutsugamsushi (Ot) groEL segment, and 1.22%(5/410)were positive for spotted fever group rickettsia (SFGR) groEL segment, and 0.49%(2/410)were positive for rickettsia mooseri (Rm) groEL segment, and 0.24%(1/410)were positive for rickettsia endosymbiont(Re) groEL segment. When analyzed the homology with other known sequences, 11Ot strains with 93.6%-100% similarities among them in this study shared the highest similarity with other Ot strains from GenBank respectively, reached up to 96.1%-100%; The groEL segments of 5 SFGR strains with 92.1%-99.5% similarities among them in this study shared highest similarity with other SFGR strains from other GenBank respectively, reached up to 98.9%-100%; In this study groEL segments of 2 Rm strains all showed 100% similarity with Wilmington strain (GenBank No:AE017197); One groEL segment of Re showed 98.9% similarity with Re strain (GenBank No:EU435143). Conclusion There were kinds of rickettsiaes infection in host animals and vector arthropods in Yunnan Province, so the monitoring and prevention of the Rickettsiosis should be strengthened.
ABSTRACT
Objective To explore the predictors on the abundance of Rattus (R.) tanezumi in households of commensal rodent plague foci.Methods Thirty natural villages that experienced previous plague cases in Lianghe county,Yunnan province,were selected followed by random selection of 20 households in each village through computer technique.Live traps were set in households to capture small mammals which were then identified to species in the field according to their morphological features.Data on potential factors for abundance of R.tanezumi were collected through questionnaires and field observation and were coded and computerized using EpiData software and further analyzed by hurdle regression model under R software.Results A total of 166 rodents (133 R.tanezumi and 33 Suucus murinus) were captured.Results from final multilevel hurdle regression model showed that the likelihood of R.tanezumi captures increased by 1.67-to 2.76-fold in households belonged to Dai ethnic families that stored foodstuff in metal pails,often raising dogs,and having adjacent houses.The number of R.tanezumi captures increased by 2.18-fold in the villages where over 80％ of the households would raise chickens.In the villages with communal latrine,the likelihood and the number of R.tanezumi capture increased 1.93-fold and 2.38-fold,respectively.While the likelihood of R.tanezumi captures would reduce by 45％-61％ in those households where there were cats and cattle being raised and maize grown in the village.The number of R.tanezumi captures would reduce by 63％ in the households where there were outside toilets.Conclusion The abundance of R.tanczumi seemed to be closely related to the ecological environment factors.Programs on plague control and prevention should relate to ecological factors that influencing the abundance of R.tanezumi.
ABSTRACT
Objective To compare the difference of biochemical characteristics and virulent Pst Ⅰ of Yersinia pestis strains in traditional focuses of plague in Yunna Province and in the new focuses of plague in Yulong County. Methods The identification data of biochemical characteristics(Rhamnose, Glycerol, Maltose, L-Arabina and Melibiose fermentation) and virulence factor(Pst Ⅰ) from different focuses of plague in Yunna Province were Retrospectively collected by tube test followed by the analysis using statistics software SAS 8.0 by Fisher exact probability of disordered two-way R × C table χ2 test. Results Among 48 strains of Yersinia pestis from hantaan type plague focus, 1 strain fermented L-maltose, 48 strains fermented Glycerol. Among 165 strains of Yersinia pestis from the Soul type plague focus, 1 strain did not ferment L-maltose, only one of them fermented Glycerol. 1 strain from the Soul type plague focus was confirmed to have mutation, for the test of nitrate reduction reaction was negative. All 5 strains of Yersinia pestis from the new focuses of plague in Yulong County fermented L-maltose and Glycerol. The statistical result showed that the differences in L-maltose and Glycerol fermentation of Yersinia pestis from different natural focuses of plague in Yunnan Province were statistically siguificant (P < 0.01). The differences of other biochemical characteristics and Pst Ⅰ were not statistically significant (P > 0.01). Conclusions Biochemical characteristics of Yersinia pestis from the hantaan type plague focus and the Soul type plague focus in Yunnan province are overlapping. Biochemical characteristics of Yersinia pestis from the new focuses of plague in Yulong County are different from those tradition focuses of plague in Yunna Province but share similarities to those from Unquiculatus focuses in North Tibet.
ABSTRACT
Objective To evaluate the risk of plague occurrence via surveying and analyzing indoor rat density and flea index in natural villages having previous plague experience. Methods During August to September 2007, 30 natural villages experiencing previous plague were selected based on the surveillance data, and then all households were coded with numbers and 20 households in each village were randomly selected via computer. Cages and sticky papers were set in 600 selected households to capture rats and fleas. Rat density, flea prevalence, flea index and median were estimated. Results One hundred thirty-three Rattus flavipectus and 33 Suncus murinus were caught and averaged rat density was 2.8 rats per one hundred cage. nights (166/6000), the median was 5 rats each village. One hundred and one mice infected fleas, flea prevalence on rats was 60.8% (101/166), 296 Xenopsylla cheopis and 48 Leptopsylla segnis were collected. Rat flea index was 2.1 fleas per rat (344/166). A total of 315 dissociated flea was caught, average dissociated flea index was 0.026 fleas per sticky paper (315/11888). The median was 5.5 dissociated fleas per village. Of dissociated fleas, Ctenocephalides felis felis (205) and Xenopsylla cheopis (103) accounted for 97.8% (308/315). The proportion for species of the rat flea and the dissociated flea was different(Fisher test: P < 0.01). The rat flea was significantly associated with the rat density(r = 0.68, P < 0.01), but the dissociated flea was significantly associated with neither the rat density(r = -yield than fried wheat batter(χ2 = 5.59, P < 0.05). Conclusions In these villages having previous plague experience of Lianghe County, Rattusflavipectus was dominant species of indoor rats, Xenopsylla cheopis and Ctenocephalides felis felis were dominant species of rat flea and dissociated flea, respectively. Mengsong, Bangdu, and Tangjiatun village had potential risk of plague emergence.