The WADI model was found to be a significant assessment of the vulnerability proxy of
incidence counts, with a moderately good fit using a negative binomial regression As a comparison model and validation tool, an alternate, non-index model was created
and also found to be significant, with a moderately good fit using a multivariate regression
All but one of the components (population density) of the alternate parsimonious non-
index model was found to be significant at the 10% level. Five (temperature, urban land use, age, unimproved water source, poverty level) out of the eight components were found to be significant at the more stringent 5% level (precipitation, female progression to secondary school and population density were below the mark)
A new WADI was created using the components that were identified as essential in the
non- index model for further validation of WADI was tested and found to be significant The original WADI derived the most statistically significant result
Geographic Information System (GIS) temporal and spatial visual output of the
vulnerable areas in the region to an increased risk of dengue transmission in the form of a map per parish per month over the period of the research study 1999-2015
Chapter 5 Discussion 5.1 Introduction Discussion
At this time, the most important arborvirus as a threat to global public health is the dengue virus (WHO 2009). Dengue has been recorded in Latin America and the Caribbean as far back as the seventeenth century, and was relegated to the background of health hazards after an aggressive public health campaign to eradicate the disease was deemed successful. The eradication process is no longer an effective option and, currently, dengue poses a threat to human health as a re- emerging infectious disease. Presently, no effective vaccine is available to combat an infection from the virus and, as a result, only supportive therapy can be used to alleviate the symptoms. This lack of options for medical intervention can lead to increased risk of morbidity and mortality in dengue endemic countries which disproportionately affect the poor, elderly and children and has an even more of a negative impact on countries in the developing world (PAHO 2014; WHO 2009).
Much-needed public health research into dengue has been limited. The WHO has deemed dengue one of the Neglected Tropical Diseases highlighting the need for evidence based public health approaches to resolve the issue (Aagnaard and Chaignant 2012). Research into dengue in the Caribbean has been limited; however, there has been some research into the larger islands of the Caribbean and also countries in Latin America. Small island nations in the Caribbean are also under constant threat from an increased risk of transmission of the dengue virus, yet the level of research has been inadequate (Schioler and Macpherson 2009). The Water Associated Disease Index (WADI) was created in order to service areas of the world that not only had a surge in re-emergent water associated diseases like the dengue virus, but also in the developing
world where resources and access to data to aid in public health research may be lacking (Dickin 2013; Dickin and Schuster 2014; Fullerton et al 2014).
Previously, the WADI has only been tested on comparatively large and populous countries such as Brazil and Malaysia. The objective of this thesis was to assess the WADI in the context of a country that is smaller, with a more homogeneous land area and a smaller population, than the countries for which it has already been assessed. The island of Dominica was chosen for this purpose. Dominica is a small island, 751 km² with a population of approximately 73,500 people in which dengue is endemic and as such was a suitable location for this evaluation. The WADI has been promoted by its creators as a vulnerability assessment tool. Given the restricted amount of public health resources available in many countries, including Dominica, the aim of the study was to explore a low cost effective measure that could be used to determine areas of vulnerability to aid in public health decision making. The WADI for Dominica was developed to determine whether or not there was an association with health outcomes on the island, namely the number of dengue cases. The research question sought to explore, through the known incidence of cases of dengue per parish, whether this tool could be informative in mapping vulnerable areas at the parish level on the island of Dominica.
In this thesis‘s statistical analysis, the dependent variable was the number of reported dengue disease cases per parish, per month. The independent variable was the synthesized WADI index value, a composite of susceptibility and exposure components, designed to measure vulnerability to an increased risk of transmission of dengue. A non-index model was also tested with a
composite of the susceptibility and the exposure factors with certain components notable as essential to the vulnerability assessment. A new WADI was created with these notable
significant outcome which will be discussed in detail, as well as, the visual output of vulnerability per parish, the Geographic Information System (GIS) derived maps.