While waiting for the development of a vacine, the only method to control or prevent the transmission dengue virus is to combat vector mosquitoes through the involment of community.. Whi
Trang 1MINISTRY OF TRAINING AND EDUCATION MINISTRY OF HEALTH
NATIONAL INSTITUTE OF HYGIENE AND EPIDEMIOLOGY
Trang 2STUDY WAS COMPLETED AT THE NATIONAL INSTITUTE OF HYGIENE AND EPIDEMIOLOGY
The scientific guidace:
1 Prof Dr Tran Ngoc Huu
2 Prof Dr Nguyen Anh Dung
Reviewer 1: ………
Reviewer 2: ………
Reviewer 3: ………
The thesis will be defended at the state thesis Council meeting at
National Institute of Hygiene and Epidemiology,
Trang 3INTRODUCTION
Dengue hemorrhagic fever (DHF) is an acute mosquito-borne viral
infectious disease and can cause of major outbreak Aedes aegypti is the
main vector transmitted disease Dengue is found in tropical and tropical climates worldwide The disease is now endemic in more than 100 countries in South-East Asia and Western Pacific regions Appropximately 40% of the world’s population live in areas where there
sub-is a rsub-isk of dengue transmsub-ission Each year, there are about 50 million dengue infections and around 500,000 individuals are hospitalized with DHF In Vietnam, DHF is local endemic and appears in rainy season Recently, each year, there are several hundred thousand infected cases and about hundred of those affected die
As of now, there is unknown specific anti-viral medicine for dengue fever and no vaccine for dengue Finding effective vector control methods in order to restraint DHF has been challenging not only for Vietnam but also for the world While waiting for the development of a vacine, the only method to control or prevent the transmission dengue virus is to combat vector mosquitoes through the involment of community
Tien Giang has the highest mortality rate of DHF in the Southern area In last few years, the disease prevention has been supported by the local government and organisations but why it hasn’t brought the high effect? Have vector control guidances met the actual local condition? How and what methods of the health education and communication for dengue vector prevention to encourage the community participation in an active and longterm effectiveness?
While waiting for the effective solution of vacine as well as other biological methods in research and trial period and to solve the current urge problem of DHF prevetion in Tien Giang, we have conducted the research: “The effectiveness of community – based method in dengue vector control in Cai Be district, Tien Giang province, 2012-2013”
Trang 4There are two objectives of this research:
1 The description of the knowledge, the attitude and the practice of the local people in the implementation of DHF control and prevention solutions and control the vector index in Cai Be district, Tien Giang province, 2012-2013
2 The assessment of the effectiveness of community – based vector control method in Cai Be district, Tien Giang province, 2012-2013
Scientific contributions and practical value:
- The intervention program is totally based on community, community work and responsibility, community selected vector control methods, participation in planning and implementing The vector control activity covered all households in the intervention areas Simple and eassy applying vector control methods were used appropriately and effective in reducing the vector index in the community
- Saving the cost of the vector control at the community was by using the vector control force as the leader of the household and students with the support and involment of the hightly respected public figures (self-management group and teachers) Each member above was considered as a collaborator of the national program and they controlled vector at their own households
- While the current communication measurement in the DHF/DF vector control have to face with many challenges in applying to each local area, the community-based vector control in this research matched the demand and the current situation
This research succeeded in mobilizing the community in practising the vector control, providing the scientific evidence in the effectiveness of the vector control This research also worked as the base
to implement the intervention at the community The result of this research can be used in the evaluation research of the effectively implementing intervention in the DHF/DF prevention as well as in providing the baseline data for future studies
Trang 5THESIS STRUCTURE
The thesis has 126 pages, 51 tables, 17 pictures and 11 appendixes
In which: The introduction and objective parts take 3 pages, the overview takes 33 pages, the method part takes 19 pages, the results part takes 34 pages, the discussion part takes 35 pages, the conclusion part takes 1 page and the recommendation part takes 1 page
The thesis has 146 references that are included 103 Vietnamese and
43 English references
Chapter 1 OVERVIEW 1.1 Definition of Dengue hemorrhagic fever/ Dengue fever
Dengue Hemoharrgic Fever (DHF) or Dengue Fever (DF) is an acute mosquito-borne disease caused by the dengue virus and can cause
of major outbreak Dengue virus belongs to the family Flaviviridae; genus Flavivirus and four serotypes of the virus have been found Aedes aegypti is a primarily vector transmitted disease
1.2 Current situation of DHF/DF
1.2.1 Current global situtation of DHF/DF
Dengue pandemic has occured in the sub-tropical and temperate climate areas, South-East Asia and Western Pacific regions are the most seriously affected According to the strategic plan of WHO from
2008 – 2015, there are about 1.8 billion (>70%) of the population at risk for dengue in South-East Asia region
1.2.2 Current situation of DHF/DF in Vietnam
DHF/DF is a local endemic disease in Vietnam, one of 10 declared infectious diseases and has the highest infection and mortality rate The populations at risk of acquiring dengue viral infections in dengue circulation regions is around 70 million
1.2.3 Current situation of DHF/DF in Southern Vietnam
The first recorded case was in the Melkong Delta, then spreaded into many epidemics with the cyle of 3-5 years In 1998, there were 123.997 cases and 347 cases of death In 2005, the dengue-infected case was at No.2 after the diarrhea in the list of 24 infectious diseases From 2006-2012, the incidence of infected cases was higher than the average of the cases from 2000-2005 In 2007, the infected rate/100.000 population was highest from 1999 but was less than 1998 In 2008, the rate of mortality/infection increased again (0.109%) The outbreak in 2010 had
Trang 6higher cases than in 2009 and the infection rate per 100.000 population increased 13.9% compared with the average of 2003-2007 From 2011-
2013, the percentage of infection and death case decreased The rate of infected cases was 72 per 100,000 population in 2014 and decreased in comparison with the rate of 2013 and the average rate of 2006-2010
Dengue virus monitoring was carried out regularly and has found four co-circulating serotypes DEN-1 virus was predominant than other serotypes during 8 years from 2006 – 2014
The number of insect in 2010 was higher than 2009 and the average of 2004-2008 The mosquito density in 2012 was in the range of 0.3-0.7 (mosquito/household) which was higher than 2011 and less than the average of 2007-2011 In 2013, the BI index was in the range of 28-50 and less than at the same time period of 2012 and remained unchanged in
2014
1.2.4 The situation of DHF/DF in Tien Giang
Tien Giang continuously had the high rate of the dengue virus infection with the circulation of 4 serotypes and the vector index changed
with none specific regulation The BI index and the average of the Aedes
condensity index were always at the high level among other Southern regions Currently, there has very small amount of budget or none for the cost of the DHF/DF disease prevention activity which has undertaken by local authorities, so the local authority also determined local people as a main force in the vector control activity However, the communication activity has limited, failed to meet the requirement in communication for changing behavior and failed to make the habit of the local people in the vector control practice through each household
1.3 The dengue vector physiology and ecology:
1.3.1 Aedes albopictus mosquitoes
The adult Aedes albopictus has a fairy small size (about 3/16 inch) and almost similar with Aedes aegypti except for a white line along the back The physilogical ecology of Aedes albopictus is the same as Aedes albopictus
1.3.2 Aedes aegypti mosquitoes
Aedes aegypti has an average size with the alternative black body with many white flakes Aedes aegypti stays horizontally The female
mosquito sucks blood and lays eggs with the active time during the daytime and at the peak in the early morning and late afternoon The
Trang 7average life expectancy of the female mosquito is 30 days The female fertilizes 4 times in a lifetime and each time with 58-78 eggs The life cycle has 4 periods and during 10-15 days
Aedes aegypti has distributed in tropical and temperate climate
areas over all continents
1.4 The dengue vector surveillance and investigation
1.4.1 Monitoring adult mosquitoes
The density index of Aedes mosquitoes is the average of the Aedes female number in an investigated household
The index of the house with mosquitoes is a percentage of houses positive for adult female mosquitoes
1.4.2 Monitoring Aedes larva: There are 4 frequently used index
The house index (HI): percentage of houses positive for Aedes
larvae
The container index (CI): percentage of all containers with water
that are Aede larva/pupa positive
Breteau Index (BI): number of Aedes positive containers per 100
houses
The larval density : The average number of Aedes larva in an
investigated household
1.5 Method and model of vector prevention
The research of antiviral vaccine against Dengue virus has been developing and going into clinical trials
In Vietnam, the DHF/DF preventive strategy is included the pilot colaborator model in 10% of the commune and province; the activity of the colaborator has reduced the vector index but not reached the requirement The research of controling epidemic result showed that the effectiveness in limiting the spread of diseases of epidemic potential Some reseachers have found several intergrated models in vector control
by using biological agents as Mesocyclops or larvivorous fishes
1.6 Some terms in the research
The water container: All containers such as large or small, which
contain water even the miscellaneous stuffs and stagnent wastewater container
Miscellaneous stuffs: The vase, waster bowl against ants, water
bowls for cattles
The waste: All the discarded items outside the house such as
Trang 8coconut shell, tires, cans, barrels, buckets, jars, jars broken
Containers with lids: all water containers have the lid, so
mosquitoes are inaccessible breeding
Water containers with larvae: water containers have Aedes aegypti and Aedes albopictus larva inside
The percentage of water containers with larvae: The percentage of
water containers with larvae inside per total number of similar water
containers
Larvae source: Any individual or category water containers with large numbers of Aedes larvae that create a large number of Aedes adults
Household: A group of people that is living in a same house,
eating together and sleep in the same house
Indoor and surrounding areas: The indoor house is an area inside
of the house with the roof against rainwater The other remaining part of the house is called surrounding area
Household without larvae: A household has none Aedes larvae in
any water containers
Community: is a social unit with the structure A group of people
shares and are bound by common characteristics and values which are set through the interaction and communication of the member
Community-driven development (CDD) or Community-based activity is a development initiative that provides control of the development process, resources and decision making authority directly to community groups
Chapter 2 METHODOLOGY 2.1 Objective
Quantitative research: Householder / representatives, students and secondary school teachers, group leaders / mass organizations and DHF vector
Qualitative research: Vice director and DHF/DF responsible staffs
of the Health Prevetive Center, the official of Secondary of Education and Training Agency, the leader of the People Committee and the Commune Health Center, head/deputy of People's Committee, leaders of mass organizations, the principal of the secondary school, head teachers and class presidents
Trang 92.2 The study location and time
The research was conducted at Cai Be district, Tien Giang province This research was operated from May 2012 until Feb 2014:
The period of assessing the current situation before the intervention from May to Oct 2012; Applying the intervention from Oct 2012 to Oct 2013; Investigating the effectiveness of the intervention from Oct 2013 – Feb
2014
2.3 Study design
Cross-sectional study described the situation before the intervention, community intervention with case control group Cross-sectional study analyzed the situation after the intervention, the before and after studies and the quantitative and qualitative studies
2.4 Sample size and sampling method
2.4.1 Quantitative research
The communes were chosen by Using purposeful sampling, in
which: 2 control communes and 2 intervention communes
The calculating formula for estimating the sample size with 2 proportions in the population:
n: the minimum sample size of each group; α, β = 0,01: level of significance; Z α/β = 1,96 95% confidance interval; Z 1- = 99%: Force sample The estimate after the intervention has the household without
Aedes larvae in the intervention group p1= 85% and the control group p2-
55%
Sample size n = 107 (the largest sample size) Because of selecting cluster group sample to increase the accuracy, the sample size will be multiplied with the DEFF = 3 (the design effect) and 5% of reserve samples Sample size after rouded up was 340
Sample size of the head of household participated in study was
340 by selecting probability cluster sampling method The selected cluster
was equal the hamlet of the commune The identified sampling interval k was the number of the house per the number of cluster Selecting the first household of each cluster was by choosing randomly Choosing the next household until reaching the required sample size in each cluster was based on the coefficient k Making the list of selected households in each
Trang 10investigated cluster was by following the route, the hamlet and management group
self-Sample size of student participated in study was 340: by selecting
probability cluster sampling method as selecting the household, the number of the cluster was equal the number of the class Selecting the first student in the cluster was by choosing randomly
Sample size of the teacher, the leader of the self-management group: the sample size for investigation was 100 teachers and 150 leaders
Using the totally sampling method, 100% teachers and 100% leaders
2.4.2 Quanlitavtive research
Purposeful sampling method:
Depth interview: A vice director in charge of professional job and
a responsible person in DHF/DF of the Health Prevention Center in district; a responsible person in charge of the secondary school in the education and training department; two CPC leaders; two principal teacher of the secondary school and two leaders of the CHS in two intervention communes
Group discussion: two discussions with the representative of hamlet and self-management group, there were 12 chosen people in each group interview Two interviews with the group of the head teacher, there were 10 selected people in each group interview There were 2 interviews with the class president and 15 selected students were chosen in each interview
The workshop with stakeholders to identify priority measures in the DHF/DF vector control had 40 people attending
2.5 The variable and evaluation index
2.5.1 The variable index
Including the information of the objective, knowledge, attitude and practice in the DHF/DF prevetion
2.5.2 The evaluation index
The proportion of the sex, the education level and occupation, the proportion of the receiving information source, the rate of having good knowledge, attitude and practice in the DHF/DF prevention The house
index (HI) with having Aedes larvae, the CI with existed Aedes larvae, the
BI, the HI with existed Aedes adult
2.6 The implement and skill for collecting information
2.6.1 The implement for collecting information
Trang 11Quantitative study: Using the questionnaire to interview directly and investigate the vector at the household through the checklists The proper knowledge, attitude and practice in DHF/DF prevention was evaluated by using marking point
Qualitative study: Using the depth interview and group discussion
2.6.2 The skill for collecting information
The quantitative investigator divided into many groups, each group had a guide and two investigators Investigator groups directed to the household followed the assigned list The group chose the respondent after the approval from the head of the household and then did the vector investigator The depth interview consisted of 2 people: one person was responsible for introducing the research and the interview content; other recorded all the information from the interview The group discussion consisted of 3 people that included a person in responsibility of introducing the research and the interview content, a person in support for the respondents about the main part in the discussion and other in recording the information from the discussion
2.6.3 The intervention
The main activity was to provide the knowledge and introduce the DHF/DF vector control community-based method in school and self-management group
Step 1: Evaluating the situation and preferences
Step 2: Developing the stakeholder group and building the steering committee to mobilize community involvement
Step 3: Training, implementing and monitoring intervention Step 4: Evaluation of implementation
2.7 Limiting the error in the study
The sample size had to calculate consistent with the design effect (DEFF) The toolkit in the study must be tested and the investigator must
be trained the skill of collecting information and investigating vector
2.8 Managing, processing and analyzing data
The data was put in Epidata 3.1 software and analyzed in SPSS 16.0 The analyzing process used the chi-squared test (χ2) and the paired t test and compared the result at the p<0.05 level for significance
2.9 Research ethics
The thesis was proved by the ethics council of National Institute
of Hygiene and Epidemiology
Trang 12Chapter 3 STUDY RESULTS 3.1 Knowledge, Attitude and Practice regarding Dengue prevention and vector indicators
Table 3.21 Knowledge, Attitude and Practices regarding dengue prevention
Control commune (n=930)
Intervened Commune (n=930)
χ 2 test, p*: compare between case and control groups
The percentage of correct knowledge, attitude and practices regarding dengue prevention in intervened group were 57.1%, 64.3% and 32.9%, respectively While the percentage in control group were 56.3%, 60.5% and 35.7%, respectively (p>0.05)
Table 3.22 Vector indicators of Dengue fever
Indicators
Control commune (n=930)
Intervened Commune (n=930)
Difference (%)
Number of water containers 2642 2861 8,29 Water containers contain
The percentages of Container Index in control and intervened groups were 34.7% and 37.0% respectively The Breteau Index of the groups were 107 and 105 respectively 62.4% of the intervened
households detected Aedes larvae while the number is 51.6% in control
group
Trang 13Table 3.23 Protection of water containers before intervention
Control Commune (n=930)
Intervened Commune (n=930) Water containers
Freq (%) Freq (%)
Difference (%)
Active/Used water containers 1498 100 1520 100 1,47
The percentage of active water containers and containers with fish
in control group were 20.53% and 9.01% respectively, while the percentages were 19.69% and 8.95% among intervened households
The percentage of active water containers in intervened group
detected Aedes larvae was 35.53%, 33.9% of abandoned water containers
detected larvae while the percentages of control group are 35.25% and 39.3% respectively
3.2 Effectiveness of vector control intervention
3.2.1 Results of vector surveillance after the intervention
The average number of Aedes larvae per household before the intervention (August 2012) was 32.47 (larvaes/household), and 3.39 (larvaes/household) after the intervention (August 2013), equivalent to a
decrease of 89.56% The percentage of water containers containing Aedes
larvae decreased from 35.54% to 11.83% (66.71% decrease equivalent) The curve shows that DI and BI of intervened group decreased significantly in comparision with the control group