Nghiên cứu đặc điểm khí hậu tương quan tới sốt xuất huyết Dengue tại 7 tỉnh ven biển Nam Bộ và hiệu quả diệt bọ gậy muỗi Aedes của ABATE 1SG ttta

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF NATIONAL DEFENCE VIETNAM MILITARY MEDICAL UNIVERSITY BUI KHANH TOAN STUDY ON CORRELATION BETWEEN CLIMATE FEATURES AND DENGUE IN COASTAL PROVINCES OF SOUTHERN VIETNAM AND EFFECTIVENESS OF ABATE 1SG LARVICIDE AGAINST AEDES LARVAE Speciality: Health management Code: 9720801 SUMMARY OF PhD THESIS HANOI - 2019 A DISSERTATION COMPLETED IN VIETNAM MILITARY MEDICAL UNIVERSITY Advisors: Nguyen Huy Nga, Ass Prof., PhD Nguyen Xuan Truong, PhD Committee member 1: Nguyen Thi Thuy Duong, Ass Prof., PhD Committee member 2: Nguyen Khac Luc, Ass Prof., PhD Committee member 3: Truong Viet Dung, Prof., PhD The dissertation will be defended by a thesis committee council in Vietnam Military Medical University At: hour date month year The thesis can be found at: National Library Military Medical University Library INTRODUCTION Vietnam is one of the world’s most vulnerable countries to climate change and sea level rising Climate change has a devastating effect on ecosystem, and one of its outcome is a range of factors which predispose to environment and health, leading to not only outbreaks of major epidemics but also obscure diseases Dengue hemorrhagic fever is an infectious disease that has been linked to climate change trends Of all regions in Vietnam, Southern coast has been significantly affected by extreme weather and climate change The incidence of dengue in this area has seen an unusual fluctuation There has been a sudden change in the frequency and characteristics of dengue fever, which obstructs disease prevention in the Southern provinces Therefore, the study of features of climate and their relationship with dengue fever is necessary Its result will help to analyze new attributes of dengue epidemic from which to come up with optimal solutions to control and prevent it in this region Research objectives: To describe the characteristics of climate and analyze its correlation with the incidence of dengue fever in Southern coastal provinces in the period of 2003-2013 To assess the effectiveness of ABATE 1SG larvicide - an intervention to kill Aedes larvae in dengue prevention and control in Rach Gia city, Kien Giang province New contributions of the thesis - The study indicated frequency of Dengue disease in coastal provinces of Southern Vietnam in the period of 2003-2013 The disease appears all the year round; the frequency of the disease is lowest in February, March, April and increases gradually from May, reaches at peak in rainfall months: July, August, September and October - The study shows that there is a clear relationship between the number of Dengue cases and climate features in the region The correlation between the number of Dengue cases correlates and temperature is close and positive with a lag of month, and months earlier (lag = -3, -2, -1); the closest correlation is at lag of months earlier The correlations between the number of Dengue cases and both rainfall and humidity are high and positive, with a lag of month and months earlier (lag = -2, -1) - The study proved that ABATE 1SG kills effectively Aedes larvae in outdoor water storage containers The results of the intervention show that the effectiveness of Abate 1SG larvicide is 100% after 24 hours; 100% after month; and maintains a high efficiency after months (98.68%) even in the outdoor condition of the water storage containers whose the levels are often changed due to the weather Outline: The thesis includes 115 pages and chapters: Introduction: 02 pages Chapter Literature review: 33 pages Chapter Research subjects and methods: 20 pages Chapter Research results: 33 pages Chapter Discussion: 25 pages Conclusion: 01 page Recommendation: 01 page References: 105 documents (45 Vietnamese papers, 60 English papers) CHAPTER LITERATURE REVIEW 1.1 Climate change in Viet Nam Statistics of rainfall over Vietnam has shown a significant increasing trend in the southern region while it has tended to decrease in the northern region In average for the whole country, the annual rainfall decreased 2% in the period of 50 years (1958-2007) Average annual temperatures in the coastal zones of Vietnam have increased significantly, from 0.5 to 0.7 oC 1.2 The characteristics of Southern coastal provinces Seven southern coastal provinces in the study include Kien Giang, Ca Mau, Bac Lieu, Soc Trang, Tra Vinh, Ben Tre, and Tien Giang They are coastal provinces in Southwestern region, is also known as the Western Region or Nine Dragon river delta Today, the region comprises 13 provinces/cities Southwestern Region is a part of Mekong Delta River with the area of 40818.3 km2, the population of 17.7 million and its population density is 435people/km2 A lot of researches have shown that Southwestern provinces are at risk flooding Our country will lose 38.9% of the total area of the Mekong Delta – the biggest rice granary of the country if the sea level rises 100cm by the end of the century Localities of Hau Giang, Kien Giang, and Ca Mau are expected to suffer the most with inundated areas up to 80.62%, 80.62% and 57.69% respectively 1.3 Dengue fever and the effects of climate change on Dengue Dengue is a mosquito-borne viral disease widely spread in tropical and subtropical regions It is a severe disease transmitted by day-biting midges It is estimated that 3.5 billion are at risk of infection with dengue viruses - 55% of the world's population The dengue virus transmission occurs from the bite of an infected Aedes mosquitoes Mosquitoes first become infected with dengue virus by feeding on the blood of a dengue-infected person and are often found in and around human dwellings The cases of dengue tend to increase in recent years Official statistics have shown that in 2008 there were 96,451 cases of dengue, and it rose to 105,370 in 2009 and in 2010 about 128,831 people suffered from dengue fever Temperature is said to affect each stage of the mosquito's life cycle.With too high or too low temperatures in the favorable survival range of Ae aegypti, egg laying time increases, causing a decrease in egg number Eggs hatch into larvae which continue their development to become pupae It is abundant in tropical regions, where environmental factors (e.g., rainfall, temperature, and humidity) and human factors (crowding population, poor hygiene) favor its life cycle Monitoring is a key component of any prevention programs and control of dengue fever because it provides the necessary information for risk assessment, response and program evaluations Supervisors can apply active or passive data collection process Vector surveillance is used to identify the main source of reproduction of mosquitoes transmitting diseases, vector susceptibility to chemical insecticides and evaluate vector control in the community Chemical measures are used to control mosquitoes that spread dengue virus in dengue outbreaks, e.g by using ABATE 1SG in water storage containers, ultra-low volume and indoor residual spraying The use of insecticides to direct against adult mosquitoes has been proved to be able stamp out epidemics in many countries around the world ABATE 1SG (transaction name ABATE 1SG) is a phosphate compound widely used in the world to kill mosquitoes that spread dengue, Japanese encephalitis, malaria ABATE 1SG is recommended by WHO because it helps to kill mosquito larvae in public health programs, and can be used for both drinking water storage containers but at doses not exceeding 1mg/litre CHAPTER RESEARCH TARGETS AND METHODS 2.1 Research target, time and place 2.1.1 Research targets * Descriptive study: - Climate features in southern coastal provinces including temperature, humidity, rainfall by month in the period of 2003-2013 - Reported cases and deaths of dengue in southern coastal provinces - Vector of dengue transmission including larvae and mosquito indices by month in Kien Giang province in the period of 2011-2013 * Intervention study: - Households and water storage containers in An Hoa and An Binh wards in Rach Gia city, Kien Giang province 2.1.2 Research place - Descriptive study: southern coastal provinces are the areas most affected by climate change, including: Tien Giang, Ben Tre, Tra Vinh, Soc Trang, Bac Lieu, Ca Mau and Kien Giang - Intervention study: An Hoa ward (intervention group) and An Binh ward (control group) in Rach Gia city, Kien Giang province 2.1.3 Research time The study was conducted within 30 months, divided into stages: - Stage 1: studying climate features correlation with dengue: 20 months - Stage 2: develop and implement intervention in the field in dengue prevention and control: 10 months 2.2 Research design Research in the community to describe climate features climate features correlation with dengue, set up intervention models in the community, including studies: - Descriptive cross-sectional studies: research on climate features correlation with dengue in southern coastal provinces - Intervention study: Develop and implement intervention in the field in dengue prevention and control in Rach Gia city, Kien Giang province 2.3 Content and methods of data collection 2.3.1 Research on climate features in the coastal areas of the southern region in the period of 2003-2013 Retrospective parameters include: - Air temperature (oC): Monthly average temperature + Monthly average temperature = Total average temperature each day in the month/total number of days in the month - Air humidity (relative humidity - %): Monthly average humidity - Rainfall (mm): monthly rainfall 2.3.2 Research on climate features and their correlations with dengue in coastal provinces in the Southern Vietnam 2.3.2.1 Characteristics of dengue in southern coastal provinces Retrospective secondary data based on data on dengue epidemics reported by the health system in the period of 2003-2013 Retrospective parameters include dengue cases and deaths: number of cases and deaths of dengue by month * Research variables and indexes: Order Variables name Collecting methods Time Calculating each period by month (2003 - 2013) Number of cases and Retrospective deaths of dengue by month Average number of Calculated by the average of the number cases and deaths of of dengue cases and deaths by month dengue by month from from 2003-2013 2003-2013 2.3.2.2 Describe the correlation between climate features and dengue: Correlation analysis (Autocorrelation): Correlation refers to the temporal correlation between past and future values of an object and phenomenon 2.3.2.3 Describe the correlation between climate features and vector of dengue transmission in Kien Giang: • Select research location: Kien Giang is a place that meets the study’s condition and has been selected for the study • Time: from 2011 - 2013 • Investigate, collect larvae and mosquitoes + Investigate and collect larvae Investigating and catching larvae place + Techniques: Use a flashlight on the water containers and use the racket to remove the larva Turn over the tray containing water available to catch Use a straw to suck the larvae into the jar Investigation of larvae in tree niches, stone niches is difficult to use a racket, use the straw that has a long pipette bulb instead Absorb water from the niche, pour it into the enamel tray to find • Identify mosquitoes’ distribution: Indicators for assessment of Aedes mosquito larvae + House Index (percentage of houses infested with mosquito larvae or pupae): HI (%) + Container Index (percentage of water-holding containers infested with larvae or pupae): CI (%) +Breteau index (BI): number of positive containers per 100 houses inspected + Pupa index (PI): number of pupae per house inspected + Mosquito density index: number of mosquitoes per house + Mosquito house index: percentage of house infested with mosquito • Study the correlation between climate features and distribution of dengue vector We have a chronological sequence (x 1, x2, , xn) with xi representing the data at time i The Mann-Kendall (S) statistical value is defined S = sign(xj - xk) = if xj>xk(j=k+1) S = sign(xj - xk) = if xj = xk(j=k+1) S = sign(xj - xk) = -1 if xj 0.05 > 0.05 p In the rainy season with rainfall of 200 mm and above, density index of mosquitoes also increased and the month of high risk of incident was July (DI = 0.69) The correlation between rainfall and BI and HI is average correlation (Pearson’s r>0.3) April is the month that mosquitoes most produce eggs, therefore HI is usually the highest in this month (38.17%) and decreases gradually at the end of the year The correlation between rainfall and DI and CI is a low correlation (Pearson’s r ≤ 0.3) Table 3.3 Correlation between temperature and insect indices, 2011-2013 Density Index Larvae Index Average Month DI (Number of temperature BI HI CI (%) mosquitoes/house) 25.91 0.32 44.40 26.17 13.48 26.54 0.28 41.09 26.15 13.74 27.71 0.40 46.66 26.88 13.66 28.39 0.46 57.29 38.17 20.57 28.52 0.47 61.07 32.77 21.06 27.92 0.51 58.69 35.54 18.98 27.44 0,69 57.29 30.25 15.74 27.66 0.54 60.49 34.24 17.11 26.93 0.48 57.76 35.30 16.15 10 27.48 0.42 53.75 31.35 14.96 11 27.41 0.45 53.60 32.42 14.49 12 26.33 0.57 46.14 31.43 13.37 Correlation coefficient r 0.081 0.402 0.403 0.302 < 0.05 < 0.05 > 0.05 p > 0.05 18 There was a significant correlation between the average temperature in the period of 2011-2013 with the insect indices, especially the average correlation between temperature and HI index and BI index (0.3