2008_Plague-Slide_Ref SR20080097
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This study analyzed the relationship between ecological factors and human plague cases in Vietnam from 1997-2006. It found that plague cases occurred most often from February to April, which corresponds to periods of high flea index and rodent density. Poisson regression modeling revealed that higher flea indices and rodent densities were independent risk factors associated with increased plague occurrence after controlling for other climatic variables like temperature, rainfall, and humidity. The results provide insights into the ecology of plague in Vietnam that can help target public health interventions.
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2008_Plague-Slide_Ref SR20080097
- 1. Human Plague: An Ecologic Study in Vietnam Hau V. Pham, Dat T. Dang, Nguyen N. N. Tran, and Tuan V. Nguyen Institute of Hygiene and Epidemiology of Tay Nguyen, Vietnam Vietnam Field Epidemiology Training Programme Office, Garvan Medical Research Institute, Sydney, Australia
- 2. Plague in the world Plague – a disease of major public health importance in endemic countries. Re-emergence in developing countries. Ecologic factors: climate, rodent density, presence of fleas.
- 3. Research Objectives Description of incidence of plague in Vietnam. Analysis of ecologic factors and its association with plague occurrence.
- 4. Setting and Time Time: 1997 – 2006 Location: the Central Highlands, Vietnam Map of Vietnam and the Central Highlands region
- 5. Study Design and Methods Case identification using standard protocol – From network of community health centers – Confirmed by Center of Preventive Medicine Rodent density = No. of rodents caught / No. trapping periods x 100. Total flea index = Flea index was derived as the ratio of total of fleas collected over the number of rodents. Ecology -- Temperature, number of sunshine hours, humidity and rainfall were recorded by local meteorological stations.
- 6. Data Analysis Outcome: actual number of plague cases. Risk factors: rodent density, flea index, and climate data. Model – Poisson regression model was used to model the relationship between the potential risk factors and plague. Analysis was conducted with the program.
- 7. Geographic Characteristics Characteristics Dak Lak Gia Lai Average elevation (m) 500 850 Temperature (oC) 23.2 1.8 22.1 1.7 Average sunshine / year (hour) 2305 239 2369 181 Average rainfall / year (mm) 1674 171 2092 290 Relative humidity (%) 83.1 6.0 84.9 6.7
- 8. Distribution of Plague Cases 1997-2006
- 9. Incidence of Plague and Mortality by Month 1 2 3 4 5 6 7 8 9 10 11 12 Month Number of cases 0 20 40 60 80 100 120 140 Number of cases Number of deaths 1 2 3 2 5 1 5 2 3 0 0 0
- 10. Rainfall and Humidity 1 2 3 4 5 6 7 8 9 10 11 12 Month Rainfall (mm) 0 100 200 300 400 1 2 3 4 5 6 7 8 9 10 11 12 Month Relative humidity (%) 0 20 40 60 80 100 Rainfall Relative humidity
- 11. Distribution of Flea Index 1 2 3 4 5 6 7 8 9 10 11 12 Month Flea index 0.0 0.5 1.0 1.5 2.0 1 2 3 4 5 6 7 8 9 10 11 12 Month Number of cases 0 20 40 60 80 100 120 140 Number of cases Number of deaths 1 2 3 2 5 1 5 2 3 0 0 0 Flea index Incidence of plague
- 12. Plague Cases and Flea Index [0.0,0.5) [0.5,0.8) [0.8,1.3) [1.3,5.3] Flea index (quartiles) Number of cases 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
- 13. Association between Ecologic Factors and Risk of Plague Occurrence 0.2 0.6 1.0 1.4 1.8 2.2 Risk ratio Density of rodent pop. (+4) Flea index (+1) Average air temp. (+20C) Sunshiness (+60 hrs) Rainfall (+160 mm) Relative humidity (+7%)
- 14. Summary and Conclusions Cases of plague occurred more often during dry season with a peak in February – April. The February – April period: high flea index and high rodent dendity. Flea index and rodent density: independent risk factors of plague occurrence.
- 15. Cong Chieng festival -- UNESCO cultural heritage Thank you