Dengue Transmission and Risk Factors in Dhaka, Bangladesh


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GRF 2nd One Health Summit 2013: Presentation by Parnali Dhar Chowdhury, University of Manitoba

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Dengue Transmission and Risk Factors in Dhaka, Bangladesh

  1. 1. Dengue Transmission and Risk Factors in Dhaka, Bangladesh Parnali Dhar Chowdhury1, C. Emdad Haque1, Robbin Lindsay2, Abdullah Brooks3,4, Michael A Drebot2 1Natural Resources Institute, University of Manitoba Microbiology Laboratory, Public Health Agency Canada 3John Hopkins University, USA, and 4 icddr,b Bangladesh 2 National GRF Davos One Health Summit 2013 17-20 November, 2013; Davos, Switzerland
  2. 2. Areas of risk for dengue disease Dengue viruses 1- 4 can cause DF / DHF Person  Aedes mosquito  Person A. aegypti
  3. 3. Estimated population at risk of dengue fever under “standard” climate change scenario: 1990, 2085 1990 2085 Decreased mosquito abatement Increased urbanization, etc. . Source. Hales S et al. Lancet (online) 6 August 2002.
  4. 4. • Dhaka, the capital of Bangladesh, 16th Largest city (15.4 million population in 2012) of the world • Estimated to grow to about 20 million (2020), making it the world’s third largest city • Population growth =~7%  Insert map of Bangladesh and Location of Dhaka • Attracts some 300-400 thousand new migrants/year Source:
  5. 5. Dengue Trends in Dhaka: Facts from Reality Dhaka : Total number of reported dengue cases by year (n = 22,705).  Asymptomatic nature of dengue (known as Dhaka fever) since 1964  First major outbreak in 2000 with 5,551 hospitalized cases (93 deaths)  Short term (2000-2008) trend reveals short cyclical pattern – reasons are unknown Dhaka: Total number of reported dengue cases, by month, 2000-2008 (n = 22,705)  Limited knowledge of dengue vector distribution and density, disease risk perception, and circulating serotypes  nearly all viruses isolated were DENV-3 (Rahman et al. 2002; Wagatsuma et al. 2004; Podder et al. 2006; Islam et al. 2006)  co-circulation of DENV3 with DENV 2 & 4 (Aziz et al. 2002) Source: (Karim et al. 2012)
  6. 6. First Outbreak in 2000 Panic situation • People • Professional • Media • Posters –Blood Test… labs. • Blaming!! BANGALI A, Mannan Dr.
  7. 7. Questions and Objectives about Dengue in Dhaka Ecological / Entomological / Virological / Socialogical-Economic Factors for Dengue What are the distribution of Aedes mosquitoes and whether Aedes density vary with different socio-economic statuses (SES)? What are the seroprevalence of DENV and how it is correlated with Aedes abundance? How human Knowledge, Attitudes, and Practices (KAP) at the individual and household levels are involved in enhancing or reducing vector habitat? Objectives:  To delineate vector distribution by examining Aedes larva and pupa breeding spaces in houses  To conduct household level serosurvey in the same household  To map risk perception and analyze KAP regarding dengue disease
  8. 8. Methodology • Multi-stage, multi-level study design for entomological survey of dengue vector distribution • Focus group discussions (FGDs) and key informant interviews (KIIs) for risk perception analysis • Guiding Principles: 2 1. Representative samples of the City of Dhaka 2. Socio-economic variability among the wards considered 3. Gender perspectives considered in FGDs and KIIs
  9. 9. Differences among Socio-economic Statuses: Some Selected Images
  10. 10. An Outline of Findings and Analysis Vector ecology and distribution during 2011 and 2012 Container analysis (mosquito breeding and larval development) and water-use pattern at household level Serosurvey result of pre- and post-monsoon 2012 Risk perception of dengue disease and its vector
  11. 11. Overview of Entomological Survey MONSOON 2011 MONSOON 2012 TOTAL LARVAE COLLECTED 2587 3644 Ae. aegypti 2128 (84%) Ae. albopictus 344 (13%) 2811 (77.1%) 634(17.4%) Other Sp. 3% 61 (1.7%) TOTAL PUPAE COLLECETED 339 1129 Survey Time House Index Container Breteau Index Index PUPAE/100 HOUSES MONSOON 2011 27.74% 32.84% 52.39% 36.02 MONSOON 2012 24.17% 31% 44.17% 169.9 Total Household Visited (target=1200) : 842 (2011) 834 (2012) Overwhelming majority of households have been found to be infested with Aedes aegypti Calculation of Stegomyia Indices are quite high for vector surveillance in both years
  12. 12. Most Frequent Container Types, Monsoon 2012  8 major types of positive containers seemed to be dominant  These 8 containers types account for 72% of all positive containers CONTAINER CODE: A1=Water tank A3=Clay pot A4=Ceramic pot A13=Metal bucket A14=Plastic bucket A19=Plastic drum (sealable) A21=Flower tub & tray A27=Tires A34= Broken sports/toy parts A38=Plastic sheets A39=Broken plastic pots
  13. 13. Images of most frequent container types, Monsoon 2012
  14. 14. Dengue Lab Diagnostics Overview HI IgG ELISA Neutralization RT- PCR 10k 1k 100 10 1 1000 100 1 0.1 10 1 0.1 400 bp  Rn Rn 10,000 10k + 1k 100 10 1 0.1 0.1 Cycle Ct
  15. 15. Serosurvey Results Pre monsoon 2012 Post monsoon 2012  1129 samples were collected  1130 samples were collected  906 (80.2%) were IgG Positive (3.6%) were IgM positive Children had lower ~ 30% seroprevalence rates (630 paired sera and 500 replacement sera)  924 (81.8 %) samples were IgG positive  Were there higher IgM positives and children seroconversions post monsoon ?
  16. 16. Confirmatory Serology + Neutralization Assays : 1. Plaque Reduction Neutralization Test 2. Microneutralization Assay Subset of “dengue IgG” positive patient sera tested by more specific neutralization assays indicated that a minority of Dhaka residents may have been exposed to Japanese Encephalitis and West Nile virus
  17. 17. Water Supply & Storing at the Household Level Based on entomological survey questionnaire Based on FGDs and KII  I cover those water holding  In the city of Dhaka, 94% (n=842)households have piped water supply with 4.6% has reliance on deep tube-well.  40.8% (n=842) households (mainly from HSES & LSES) store water for multiple reasons.  38.4% household members empty/clean containers on weekly basis, whereas 59.6% empty water more than weekly basis and no idea of cleaning the water holding containers. containers which I use only for cooking but not for other purposes (Female respondent from MSES)  We have no choice but to store water everyday as we don’t have 24 hours supply of electricity(Respondent from LSES)  We don’t store water in our house. However, I have no idea whether our housemaids are storing water or not as they are not allowed to use our toilets(Respondent from HSES) HSES=High Socio-economic Status; MSES=Medium Socio-economic Status; LSES=Low Socioeconomic Status
  18. 18. Knowledge about Dengue Vector Breeding Sites  Respondents (n=15) do not fully recognize breeding sites of the dengue vector.  Respondents associated other “dirty” sites (i.e.,sewage drains, waste sites) where they found lots of larvae and adult mosquitoes.  There is a marked hierarchy of people’s perceptions of dengue vector breeding sites. Sites outside the home were ranked as highly probable breeding sites, while containers in the houses were ranked as less likely breeding sites.  Dengue mosquitoes breed everywhere.  Dengue mosquitoes grow in stagnant water but I never knew about that water has to be clean not dirty.  I know mosquitoes those bite, mostly breed from outside containers and they don’t lay eggs inside houses.  All biting mosquitoes come from outside to the inside of our houses to bite us.
  19. 19. Relation of demograph, KAP and Vector
  20. 20. Risk Perceptions of Dengue Disease and Vector  Perception of dengue vector: its dilution with other mosquitoes I know that dengue disease is caused by striped mosquitoes. Though this disease is fatal, they come once a year or every two years. It is less severe when we think of how often we are annoyed by other mosquitoes, which come daily, all the time and everywhere Dengue is not a problem in Dhaka, why should I worry about dengue mosquito then? (HSES respondent)  Perception of dengue as a disease:Partial knowledge with misconception I know dengue is caused by dengue mosquito bites but I don’t have any idea about dengue fever or DHF Dengue is like a mild fever, it never became severe to people in our country
  21. 21. Conclusions and Implications  Vector and sero survey related: significant overlap ;high degree of exposure (high degree of dengue seroprevalence, risk for 2nd exposure – >DHF)  Differential water storage and water use patterns are profoundly influenced by varied utility supplies and constraint in services (e.g. piped water, electricity) to different socio-economic categories of city dwellers  A sense of complacency about dengue disease exists across socioeconomic categories but their reasons are rooted in varied macro level contexts  The degree of misconception about dengue transmission is quite high, and risk communication on dengue disease needs to be strengthened among the community stakeholders  Single disciplinary approach is not adequate to encompass complexities in dengue transmission, and application of an Ecohealth approach would be appropriate
  22. 22. Acknowledgement Thesis Committee Personnel: C. Emdad Haque (UM) Michael Drebot (PHAC) Robbin Lindsay (PHAC) Stephane McLachlan (UM) Institutions: International Centre for Diarrh Disease, Bangladesh (icddr,b) North South University (NSU), Dhaka, Bangladesh Population Services and Training Centre (PSTC), Bangladesh Public Health Agency Canada (PHAC) Government: Ministry of Health & Family Welfare, Govt. of Bangladesh Funding Agencies: IDRC-CRDI, Canada IDRC Doctoral Research Award Manitoba Health Research Council (MHRC) Graduate Fellowship University of Manitoba (UM)
  23. 23. Parnali and Robbin Lindsay Parnali ???
  24. 24. Questions ?