Epidemiological analysis of plague in Qinghai province between 2000 and 2009 / 中国地方病学杂志

Objective To analyze the endemic features of plague in Qinghai province between 2000 and 2009, discover the law of occurrence and progression, in order to provide a scientific basis for further prevention and treatment of the disease. Methods Descriptive epidemiology was employed to analyze the data from on the spot investigation, monitoring reports and papers published between 2000 and 2009. The indicators included the area, host and media distribution of animal plague and area, time, and population distribution of human plague.Results In Qinghai province between 2000 and 2009, 189 strains of Yersinia pestis were isolated from a variety of animals and insect vectors, including 77 from the marmot, accounting for 40.74%, 40 from Callopaylla dolabris,accounting for 21.16%. Positive serum antibodies against F1 plague were detected in 238 samples, including 90 samples from husbandry dogs, 63 from woodchucks. The areas with Yersinia pestis were consistent with the areas with positive serum antibodies against F1 plague, which distributed mainly along the Qinghai-Tibet railway Wulan county, Delhi and Golmud Multi-county;confirmed that there was natural foci of plague in Qinghai vole. Between 2000 and 2009, 13 events of human plague occurred, with 37 cases and 16 patients died, mortality was 43.24%.Cases were distributed in 11 townships of Tongde, Xinghai, Qilian, Wulan, Tianjun, Nangqian, Qumalai,Chengduo and Zhiduo counties. May to October was the disease season, with September the peak. Pneumonic plague disease type was the main mode of transmission of the plague and patients often contacted with airborne droplets through the air and peeling fresh Marmota. Conclusions Plague in Qinghai province is still grim,strengthening animal plague surveillance, and timely disposal of animal plague, improving the province's agricultural and pastoral areas, especially increase the disease prevention consciousness of the masses are future tasks. Work should be focused on strengthening the prevention and control of plague along Qinghai-Tibet railway,and prevent the occurrence and long-distance transmission of human plague.

Different strategies for preparation of non-tagged rV270 protein and its efficacy against Yersinia pestis challenge / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>LcrV is an important component for the development of a subunit vaccine against plague. To reduce immunosuppressive activity of LcrV, a recombinant LcrV variant lacking amino acids 271 to 326 (rV270) was prepared by different methods in this study.</p><p><b>METHODS</b>A new strategy that produced non-tagged or authentic rV270 protein was designed by insertion of rV270-thrombin-hexahistidine fusion gene into the vector pET24a, or by insertion of hexahistidine-enterokinase-rV270 or hexahistitine-factor Xa-rV270 fusion gene into the vector pET32a. After Co(2+) affinity chromatography, a purification strategy was developed by cleavage of His tag on column, following Sephacryl S-200HR column filtration chromatography.</p><p><b>RESULTS</b>Removal of His tag by thrombin, enterokinase and factor Xa displayed a yield of 99.5%, 32.4% and 15.3%, respectively. Following Sephacryl S-200HR column filtration chromatography, above 97% purity of rV270 protein was obtained. Purified rV270 that was adsorbed to 25% (v/v) Al(OH)₃ adjuvant in phosphate-buffered saline (PBS) induced very high titers of antibody to rV270 in BALB/c mice and protected them (100% survival) against subcutaneous challenge with 10⁶ CFU of Y. pestis virulent strain 141.</p><p><b>CONCLUSION</b>The completely authentic rV270 protein can be prepared by using enterokinase or factor Xa, but they exhibited extremely low cleavage activity to the corresponding recognition site. Thrombin cleavage is an efficient strategy to prepare non-tagged rV270 protein and can be easily operated in a large scale due to its relatively low cost and high cleavage efficacy. The recombinant rV270 can be used as a key component to develop a subunit vaccine of plague.</p>

Evaluation of immunization protection efficacy of plague subunit vaccine / 中华预防医学杂志

<p><b>OBJECTIVE</b>To evaluate the protective efficacy of plague subunit vaccine, BALB/c mice, guinea pigs and rabbits were used in this study.</p><p><b>METHODS</b>Groups of mice (10 per group), guinea pigs (14 per group) and rabbits (6 per group) were immunized with F1 + rV270 vaccine, EV76 vaccine and alum adjuvant by intramuscular route, respectively. Serum antibody titres of mice, guinea pigs and rabbits were determined by ELISA and the immunized animals were challenged with 10(6) CFU of Y. pestis strain 141 at the 8th week after the primary immunization.</p><p><b>RESULTS</b>The immunized mice, guinea pigs or rabbits with subunit vaccine developed anti-F1 IgG titre of 41 587.3 +/- 2.1, 11 543.7 +/- 2.1 or 522.4 +/- 22.4 and elicited statistical anti-F1 IgG titre difference among them (F = 17.58, P < 0.01). The immunized mice, guinea pigs or rabbits with subunit vaccine had anti-rV270 IgG titre of 15 748.7 +/- 1.6, 12.6 +/- 1.4 or 1648.0 +/- 5.0 and induced statistical anti-rV270 IgG titre difference among them (F value was 16.34, P < 0.01). There was significant anti-F1 IgG titre difference among mice, guinea pigs and rabbits immunized with EV76 vaccine that developed anti-F1 IgG titre of 913.4 +/- 4.5, 937.0 +/- 2.0 or 342.0 +/- 12.0 (F = 23.67, P < 0.01), whereas the immunized mice, guinea pigs and rabbits with EV76 vaccine developed anti-rV270 IgG titre of 12.0 +/- 1.0, 447.0 +/- 10.0, 40.0 +/- 11.0 and there was no anti-rV270 IgG titre difference between them (F = 2.20, P = 0.1314). The immunized mice with subunit vaccine developed significantly higher anti-F1 IgG titres than immunized guinea pigs and rabbits (q value was 30.57 and 19.04, respectively, P < 0.01), and there were no anti-F1 IgG titre differences between the immunized guinea pigs and rabbits (q = 0.04, P = 0.8485). The immunized mice with subunit vaccine developed significantly higher anti-rV270 IgG titres than immunized guinea pigs and rabbits (q value was 27.10 and 19.49, respectively, P < 0.01), and there were no anti-rV270 IgG titre differences between the immunized guinea pigs and rabbits with the subunit vaccine (q = 0.25, P = 0.6187). The immunized mice with EV76 elicited higher anti-F1 IgG titres than immunized guinea pigs and rabbits (q value was 40.67 and 29.10, respectively, P < 0.01), whereas there was no difference of F1 IgG titer between immunized guinea pigs and rabbits (q = 0.06, P = 0.8098). The immunized mice, guinea pigs and rabbits with subunit vaccine provided 100% (10/10), 86% (12/14) and 100% (5/5) protection against 10(6) CFU Y. pestis of challenge, respectively. The immunized mice, guinea pigs and rabbits with EV76 vaccine gave 100% (6/6), 93% (13/14) and 100% (6/6) protection against 10(6) CFU Y. pestis of challenge respectively.</p><p><b>CONCLUSION</b>BALB/c mice is the best small animal model for valuation of protective efficacy of plague subunit vaccine. The guinea pigs showed a high individual variation for this purpose. The rabbits can be used as an alternative model for evaluating plague subunit vaccine.</p>

Investigation on the space structure of plague natural foci in the Sanjiangyuan area in Qinghai Province / 中国地方病学杂志

Objective To investigate the space structure of plague natural foci in the area of Lantsang, Yellow and Yangtse River in Qinghai Province to provide references for making decisions to eontrol the occurrence of human plague. Methods Data was collected from the survey on natural foci and surveillance of plague from 1954 to 2006 and descriptive epidemiological method was used to analyze the data. Results Marmata hirnalayana and Microtus fuscua natural foci were known in Sanjiangyuan area. Callopsylla dolabris, Oropsylla silantiewi, Citellophilus sparsilis and Amphipsylla tuta were vectors; Microtus fuscus plague natural foci was in a range of about 9500 km2, distributing in Zhenqin Town, Chengduo County. Marmata himalayana plague natural foci distributed over 13 countries, a range nearly 107 000 km2. By the end of 2006, 450 strains of Yersinia pestis were detected and separated from 6 kinds of rodents, 6 kinds of carnivora, 3 kinds of artiodactyls and 9 insects vectors. Between 1960 and 2006, 238 cases and 134 deaths from plague were reported. Most human plague cases occurred in the months from May to November and usually presented as one of three primary forms-bubonic 17.23%(41/238), septicemic 16.81% (40/238), pneumonic 61.34% (146/238) and other types 4.62% (11/238). However, the first epidemic plague case was mainly the glandular plague. Conclusions Date suggested that plague is still a critical public health problem in Sanjiangyuan area, against which countermaeasure needs to be strengthened in the main epidemic areas. More scientific researches on plague should be carried out. Surveillance networks of reporting suspected plague have been established and reduce the number of human plague cases.

Study on plague pathogeny in areas along Qinghai-Tibet Railroad in Qinghai from 2001-2006 / 中国地方病学杂志

Objective To study the features of Yersinia pestis(Y.pestis)in areas along Qinghai-Tibet Railroad in Qinghai Province.Methods To identify the biologic types and the molecular biological feathers of Y.pestis isolated from areas along Qinghai-Tibet Railroad in Qinghai from 2001-2006.Results All the tested Y.pestis was biologically of classical type and ecologically of Qinghai-Tibet plateau type.The Y.pestis had high virulence.The Y.pestis of 65×106 plasmids was distributed in the Tanggula area,the Y.pestis of 52×106plasmids,in Tianjun and Delingha areas.The Y.pestis srains carried 52 × 106 plasmids.except the two containing 65 X 106 plasmids in Wulan County.The genetic type of Y.pestis in Tanggula was type 5 and that in Zongwulong of Delingha,Saishike,Keke,Tongpu of Wulan was type 8 except 2 strains of Y.pestis isolated from woodchuck and the patients in Dananwan of Tongpu,Wulan County were type 15.Conclusion The Y.pestis in the area along Qinghai-Tibet Railroad in Qinghai belongs to Qinghai-Tibet plateau type with high virulence.

A sero-epidemiologic survey on human plague in source of three rivers area Qinghai from 2005 to 2007 / 中国地方病学杂志

Objective To explore the characteristics of human plague using a sero-epidemiologic method in the source of the three rivers area in Qinghai for possible plague control strategies. Methods Investigate human plague sero-epidemiologically in the source of 4 counties in the three rivers area in Qinghai. The human serum would be tested to confirm the sew-positive rate for plague F1 antibody using indirect hemagglutination assay(IHA). Results A total of 2508 local participants were tested in 4 counties, the overall plague sero-positive rate was 2.31%(58/2508). This represents a statistically significant difference with 4 counties(X2=19.30,P<0.01). The sew-positive rate for males and females were 2.54% (32/1261) and 2.09% (26/1247), respectively. There were no statistically significant differences between males and females(X2= 0.65,P 0.05). The sero-positive rate in herdsman, cadre, Tibetan, Hart nationalities were 3.54% (44/1243), 6.47% (11 / 170), 2.40% (56/2335) and 1.47% (2/136), respectively. The sero- positive rate increased with age. The highest titre for human plague serum antibody was 1 : 640. Conclusion There were occult infections of plague in the population on source of three rivers area in Qinghai. Sero-epidemiologic data revealed that the human plague sero-positive rate was closely correlated with the local animal plague.

A molecular epidemiological study on human plague fulminant epidemic in Qinghai, 2004 / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the epidemiology of genotyping Yersinia pestis isolated in the fulminant epidemics of human plague in Qinghai province in 2004.</p><p><b>METHODS</b>Primer pairs targeting the twenty-three different identified regions (DFRs) were designed to detect the presence or deletion of each DFR in 13 strains of Yersinia pestis isolated from the fulminant epidemic of human plague in Qinghai province in 2004.</p><p><b>RESULTS</b>There were 4 genomovars, i.e. Genomovar 8, 10, 15 and 16 in the 13 strains of Yersinia pestis identified. The genomovar of all the strains of Yersinia pestis isolated from Nangqian county was Genomovar 10. Among the two strains of Yersinia pestis isolated from Wulan county, the genomovar of one strain was Genomovar 8 and the other was Genomovar 10. The genomovars of all the strains of Yersinia pestis isolated from Qilian, Qumalai and Chengduo county belonged to Genomovar 16.</p><p><b>CONCLUSION</b>It was demonstrated that the genotyping of Yersinia pestis appeared to be a powerful tool for investigating human plague epidemics.</p>

Study on an epidemic of human lung plaque in Nangqian county, Qinghai province / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study an epidemic of human lung plague fulminant from September to October, 2004 in Nangqian county, Qinghai province.</p><p><b>METHODS</b>Cases were diagnosed through data from epidemiological, clinical, bacteriological, serological and autopsy studies.</p><p><b>RESULTS</b>14 patients were identified, ending up with 6 deaths and 8 cured. The first case was diagnosed as primary pesticemia late progressed to lung plague. 4 cases were transformed from pesticemia out of 13, leaving the 9 cases as primary lung plague. Situation was under complete control through routinely handling the plague focus.</p><p><b>CONCLUSION</b>The first case was bitten by the infected fleas which parasitized the marmota preyed on a dog but later these fleas were brought into the tent by the dog. The others cases were infected through droplets or dust. Programs on monitoring and controling the amount of marmotas and fleas should to be strengthened to prevent the epidemics of plague in the area.</p>