From 1991 to 2000 the plague in Viet Nam has remarkably controlled. The morbidity and mortality rate decreased from 439.6 patients/year during 1991-1995 to 161.2 patients/year during 1996-2000, the areas affected by plague had been narrowed, only in Gia Lai and Dac Lac provinces. The plague occours throughout the year but concerntrating in period from February to May every year. In the North, R.norvegicus is the main host and R.exulans is the common host at the other areas. The main vector of plague in Viet Nam is X.cheopis. Biological surveillance showed that: Y.pestis has been negative at the provinces and cities in the North for the past years. The possitive rate was different in the rest areas over the times
Plague ; Epidemiology ; Prevention & control

This paper aims to examine the preventive measures taken against the plague in colonial Korea, particularly as applied to the control of Chinese coolies in 1911, soon after the annexation. The Government General of Korea began preventive measures with a train quarantine in Shin'uiju and Incheon in response to the spread of the plague to the Southern Manchuria. Shin' uiju had become urbanized due the development of the transportation network, and the seaport of Incheon was the major hub for traffic with China. Examining the transportation routes for the entry and exit of Chinese to and from Korea makes clear the reason why the Korea Government General initiated preventive measures in mid-January, 1911. The Government General of Korea tried to block the entry of Chinese through the land border crossing with China and through ports of entry, primarily Incheon. During the implementation of the preventive measures, quarantine facilities were built, including a quarantine station and isolation facility in Incheon. It was also needed to investigate the population and residential locations of Chinese in Korea to prevent the spread of plague. A certificate of residence was issued to all Chinese in Korea, which they needed to carry when they travelled. The preventive measures against plague which broke out in Manchuria were removed gradually. However, there was no specific measures against Chinese coolies, those who had migrated from China to work in the spring in Korea. Still the Government General of Korea had doubt about an infection of the respiratory system. As a result, the labor market in colonial Korea underwent changes in this period. The Government General recruited Korean laborers, instead of Chinese coolies whose employment had been planned. This move explains the Government General's strong preventive measures against plague and uncertainty in the route of plague infection, which influenced subsequent regulations on the prohibition of Chinese coolies working on the public enterprise sites and the improvement of labor conditions for Korean laborers.
China/ethnology ; Colonialism ; History, 20th Century ; Humans ; Korea ; Plague/*history/*prevention & control ; Quarantine/*history

OBJECTIVETo study the risk classification of animal plague in Spermophilus Dauricus Focus, using the Best Subsets Regression (BSR) model.

METHODSMatlab, BSR and exponential smoothing were employed to develop and evaluate a model for risk classification as well as to forecast plague epidemics at the Spermophilus Dauricus Focus. Data was based upon the Inner Mongolia surveillance programs. This model involved 7 risk factors, including density of Spermophilus dauricus, percentage of hosts infested, host flea index, percentage of nests infested, nest flea index, percentage of runways infested, and runway flea index.

RESULTSForecasting values of the classification model(CM)were calculated and grouped into 3 risk levels. Values that over 2/3 of the CM would indicate the existence of potential epidemics while those below 1/3 would indicate that there were no risk for epidemics but when values that were in between would indicate that there exist for high risk. Annually, during the observation period in the Inner Mongolia Spermophilus Dauricus Foci, the detection of Yersinia pestis gave a risk rating value of 1 which stood for existing epidemics, while nil detection rate generated a 'zero' value which representing the situation of non-epidemic. The overall plague epidemics forecasting surveillance programs in 2012 at the Spermophilus Dauricus Foci indicated that no active plague was observed. When the forecasting values became over 2/3, combinations of all the risk factors would achieve the consistency rates of 100%. When the forecasting values were below 1/3, combinations of at least the first 4 factors could also achieve the consistency rates of 100%. However, when the forecasting values fell in between, combinations of at least the first 4 factors would achieve the consistency rates of around 50%.

CONCLUSIONResults from our study showed that plague would not be active to become epidemic, in 2012.

Animals ; China ; epidemiology ; Plague ; epidemiology ; prevention & control ; Risk Assessment ; Rodent Diseases ; epidemiology ; Sciuridae ; Yersinia pestis

Pneumonic plague that originated in Russian Siberia broke out in Northeast China in October 1910-March 1911. On the basis of field visits, autopsy, bacteriological identification, and close collaboration with local authorities and international colleagues, Dr. Wu Lien-Teh implemented a series of efficient antiplague measures, which successfully controlled the development of an extraordinary epidemic plague. In his subsequent work, Dr. Wu demonstrated the respiratory transmission of pneumonic plague and tarbagans' role in this spread. Dr.Wu's academic and cultural contributions are valuable in the medical progress in China.
China ; Epidemiology ; history ; History, 20th Century ; Humans ; Plague ; history ; mortality ; prevention & control ; transmission

The risk of plague epidemics and relapse of various types of plague foci persists in Inner Mongolia Autonomous Region. For Marmota sibirica plague foci, the animal plague has not been found but antibody has been detected positive. Nowadays, Marmota sibirica has been increasing in population and distribution in China. In bordering countries Mongolia and Russia, the animal plague has been continuously prevalent. For Spermophilus dauricus plague foci, the animal plague has been taken place now and then. Compared to the above foci, the animal plague is most prevalent in Meriones unguiculatus plague foci and frequently spread to humans. Due to higher strain virulence and historical disaster in Marmota sibirica plague foci and Spermophilus dauricus plague foci, plague prevention and control should be strengthened on these foci. In addition to routine surveillance, epidemic dynamics need to be further monitored in these two foci, in order to prevent their relapse and spread to humans.
Animals ; China/epidemiology* ; Epidemics ; Humans ; Plague/prevention & control* ; Prevalence ; Sciuridae ; Yersinia pestis

Since plague is an important natural focus zoonosis, the typing of natural plague foci becomes one of the elements in understanding the nature and developing related prevention program of the disease. Natural foci of plague are composed by four fundamental parts which include Eco-geographical landscape (natural plague foci), hosts, vectors and pathogens (Yersinia pestis) that comprehensively interact through the large temporal scale of evolution. Human activities have had great impact on the foci of natural plague. Based on the published serial research papers, we tried to integrate the knowledge of each factor in natural plague foci and focusing on theoretical aspects, so as to strengthen the prevention and surveillance programs of plague to be extrapolated to other zoonosis.
Animals ; Biological Evolution ; China ; epidemiology ; Disease Reservoirs ; Geography ; Insect Vectors ; Plague ; epidemiology ; prevention & control ; Yersinia pestis ; genetics

OBJECTIVETo evaluate the protective efficacy of plague subunit vaccine, BALB/c mice, guinea pigs and rabbits were used in this study.

METHODSGroups 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.

RESULTSThe 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.

CONCLUSIONBALB/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.

Animals ; Antibodies, Bacterial ; blood ; Dose-Response Relationship, Immunologic ; Female ; Guinea Pigs ; Immunization ; Immunoglobulin G ; blood ; Mice ; Mice, Inbred BALB C ; Models, Animal ; Plague ; prevention & control ; Plague Vaccine ; immunology ; Rabbits ; Vaccines, Subunit ; immunology

Recombinant Fl-V (rFl-V) fusion protein is the main ingredient of the current candidate vaccine against Yersinia pestis infection, which has been under investigation in clinical trial in USA. We investigated the soluble expression conditions of rF1-V in Escherichia coli BL21 (DE3) that we constructed before. After scale-up and optimization of fermentation processes, we got the optimized fermentation process parameters: the culture was induced at the middle exponential phase with 50 µmol/L of IPTG at 25 °C for 5 h. Soluble rFl-V protein was isolated to 99% purity by ammonium sulfate precipitation, ion exchange chromatography, hydrophobic chromatography and gel filter chromatography. The protein recovery was above 20%. Protein identity and primary structure were verified by mass spectrometry and Edman sequencing. Results of purity, quality and western blotting analysis indicated that the target protein is a consistent and properly folded product. Furthermore, the immunogenicity of various antigens formulated with aluminum hydroxide adjuvant was evaluated in mice. Serum antibody titers of 4 groups including 20 µg rFl, rV and rFl-V and 10 µg rFl+10 µg rV, were assayed by ELISA after 2 doses. The antibody titers of anti-Fl with 20 µg rFl-V were obviously higher than titers with other groups; meanwhile there were no significant difference of anti-V antibody titers among them. These findings confirm that rFl-V would be the active pharmaceutical ingredient of the plague subunit vaccine.
Adjuvants, Immunologic ; Animals ; Antibodies, Bacterial ; blood ; Antibody Formation ; Antigens, Bacterial ; immunology ; Blotting, Western ; Chromatography, Ion Exchange ; Enzyme-Linked Immunosorbent Assay ; Mice ; Plague ; prevention & control ; Plague Vaccine ; immunology ; Recombinant Fusion Proteins ; immunology ; Vaccines, Subunit ; immunology ; Yersinia pestis

China ; epidemiology ; Female ; History, 19th Century ; History, 20th Century ; Humans ; Male ; Plague ; epidemiology ; history ; prevention & control ; Portraits as Topic ; Public Health ; history

OBJECTIVELcrV 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.

METHODSA 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.

RESULTSRemoval 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.

CONCLUSIONThe 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.

Amino Acid Sequence ; Animals ; Antibodies, Bacterial ; blood ; Antigens, Bacterial ; genetics ; immunology ; Blotting, Western ; Cloning, Molecular ; Electrophoresis, Polyacrylamide Gel ; Escherichia coli ; genetics ; Female ; Genetic Vectors ; Mice ; Mice, Inbred BALB C ; Molecular Sequence Data ; Plague ; immunology ; prevention & control ; Plague Vaccine ; genetics ; immunology ; Plasmids ; Pore Forming Cytotoxic Proteins ; genetics ; immunology ; Protein Engineering ; methods ; Recombinant Fusion Proteins ; genetics ; immunology ; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ; Survival Analysis ; Vaccines, Subunit ; genetics ; immunology ; Yersinia pestis ; growth & development ; immunology