Dengue has become an increasingly important public health problem in the tropical world in terms of morbidity and mortality. With rapidly changing human population and activities, the ecology of both the pathogens and vectors, climate variability/change coupled with weak health systems, dengue outbreaks are likely to become more frequent. In our approach, we addressed the reality that effective prevention and control of dengue cannot be achieved from narrow perspectives, but would largely benefit from a holistic approach that considers an improved understanding of SES and health system readiness. The basic idea of SES is to be explicit in system thinking and linking together the ‘human system’ and the ‘natural system’ in a two-way feedback relationship.
The interactions between humans, pathogens and environment, suggest that SES is crucial in disease occurrence and transmission dynamics. Moreover, the readiness of national and sub-national levels in dengue mitigations is central in the designing and planning of appropriate intervention measures. It is against this background that we conducted this analysis to identify socioecological factors and readiness of the districts in the control and prevention of dengue. In our data collection process, we adopted a consultative workshop method, which has been found to foster engagement through collaborative discussions and constructive feedback between participants from different organizations and facilitators on a particular topic [34–35]. The approach helped us to obtain information-rich data and persistent observation on dengue management and control in the study districts from purposively selected key stakeholders, which is similar to a consideration reported elsewhere [36].
In the SES framework analysis, we found that the ecological descriptors of Ilala and Kinondoni were characterised by both urban and peri-urban ecosystems with planned and unplanned settlements. Although in our study we did not establish the impact of urbanization on the occurrence of dengue, urban and peri-urban areas have been reported to be vulnerable to the disease, the outcome which is driven by rapid and uncontrolled urbanization that support Aedes mosquito productivity [2, 37–38]. The intrapersonal factors such as in-house water storage, improper household waste water disposal were common practices in the districts. The presence of potential mosquito breeding sites including discarded automobile car tyres, flower pots and water stagnation were reported to support habitat suitability for mosquito breeding and thereby increasing the risk of occurrence of dengue in the two districts [2, 21].
It was reported that to date, there have been no effective measures in the disposal of used automobile tyres. As a result, they were improperly discarded and continued to stockpile in the districts. Tyre stockpiles create a great health risk as they provide permissive breeding grounds for mosquitoes [39]. Used automobile tyres and domestic water storage containers have been reported as the most important larval habitats for Ae. aegypti in Dar es Salaam and Zanzibar [40–41]. These observations suggest that the solution to proper management of mosquito breeding sites does not fall clearly within the boundaries of a single discipline or sector but rather a multi-sectoral approach.
Vulnerability to dengue was considered disproportionately distributed within each of the study districts. This suggests that interventions to address them should be repackaged based on specific-area risk profiles. However, as we have highlighted on the inefficiency of surveillance systems based on district-level SES framework analysis, we cannot account explicitly on the representation of vulnerability of sub-district levels to dengue. SES framework analysis at the sub-district levels is likely to complement our understanding on the vulnerability profiles at different ecological levels.
One of the strategic mosquito prevention measures in the districts was larviciding. However, in the two districts, larviciding, which was introduced for malaria control [42], was implemented without consideration of the evidence to guide appropriate timing, areas and potential breeding sites of focus. We suggest that in order to effectively prevent dengue, it is important to implement the integrated vector management measures. This should be implemented by targeting the most suitable mosquito habitats to suppress mosquito larval stages thereby reducing adult emergence. Although larviciding has been recommended as a complementary intervention to control malaria [43], we suggest to conduct monitoring and evaluation of such interventions against the Aedes mosquitoes.
It has been established that indices of mosquito and climate factors are the main determinants of dengue [44–46]. Since microclimate dynamics is largely determined by human activities it is imperative to suggest that a key strategy to prevent and control dengue is to focus on addressing the anthropogenic factors. A number of ecological, biological and social factors are involved in mosquito breeding and pathogen transmission [47]. A study in Sri Lanka revealed that dengue outbreaks were significantly associated with ecological, socio-economic and demographic factors; including the presence of built-up area, and areas with higher human population density [48]. Existing evidence on the complexity of eco-bio-social contexts repeatedly argues that dengue control necessitates sound intersectoral approaches that combine environmental management practices with community mobilization [49–51]. Probably intensification of public health education on proper management of water storage containers, discarded car tyres, periodic draining or removal of artificial containers could be the most effective strategy of reducing mosquito breeding habitats. Based on SES framework analysis results, we hypothesise that interventions on the management of potential mosquito breeding sites in domestic and peri-domestic environments and ecological health could generate data to guide sustainable community-based prevention strategies against dengue and other Aedes-borne viral diseases.
On assessing the capacity in responding to outbreaks, none of the two districts reported the readiness in the management of dengue outbreak. The availability of disease surveillance and management guidelines in English language was reported as a utilization impediment and participants proposed that they should be translated into Kiswahili. In our study, the guidelines were reported to be voluminous and not user-friendly. Since a number of guidelines continue to proliferate on the same or similar subjects, it is likely impractical for the practitioners to use them efficiently. The successful implementation of guidelines depends on many factors including participatory development, dissemination and implementation strategy as well as evaluation of their effectiveness [52]. The presence of guidelines may not guarantee their implementation or utility, and some studies have reported failure of guidelines to influence the implementation of health programmes [53–55]. The reasons that have been associated with failure of guidelines to achieve their objectives, include inadequate consultation, lack of consideration of technical capacity, attitude and behaviour of health professionals and lack of training on the use of the guidelines [56–58]. Adoption of a web- or mobile-based electronic platform to enhance, on the one hand data collection especially at community level and on the other, prompt searching by topic of interest or based on prevailing needs is likely to be a breakthrough. We believe that with increasing occurrence of infectious disease epidemics the efficiency of disease surveillance, early detection and early warning will require use of such web or mobile technologies [59]. This can be enhanced through application of machine learning data-mining integration with socio-ecological and geospatial analyses [60], specifically designed for low- and middle- income countries like Tanzania.
The capacities of the districts in dengue epidemic readiness was limited, and this calls for concerted efforts to improve resource availability, and training. Measuring readiness in epidemic preparedness and response is likely to present some challenges. This is because in this study epidemic preparedness focused mainly on human resource, infrastructure, and surveillance. The study did not document the relevant processes in epidemic preparedness or the activities executed during an epidemic response, including isolation and quarantine, public communication, and others [61].
Generally, the overall performance of the surveillance system in the two districts was not satisfactory in detecting and or monitoring trends of dengue. We recorded inadequate skills and capacity in outbreak investigation, insufficient laboratory supplies, poor surveillance data quality, inadequate data management including data analysis, interpretation and use, and poor information/data sharing practices between sectors. The surveillance systems were reported to be inefficient with inadequate involvement of community and therefore not tailored for early detection and response. Limited or no evidence of routine data analysis at sub-national levels mainly due to lack of clear guidelines on how and when to analyse data has been reported in previous studies [62–65]. It has been described that when the health facilities do not analyse and use the data, the utility of the surveillance system becomes minimal, which makes the system too weak to pick outbreaks early that could guide prompt response. The absence of data analysis, interpretation and utilization for local action seen in the present study is in line with findings of studies in Ethiopia and Nigeria [66–68]. Skill gap in data management system, weak supervision and feedback system, low or no legal enforcement to the surveillance activities, lack of incentives, lack of continued capacity building training, and lack of sense of ownership have been reported as factors affecting analysis and use of surveillance data [66].