Strengthening the perception-assessment tools for dengue prevention: a cross-sectional survey in a temperate region (Madeira, Portugal)

Aedes aegypti is one of the most competent vectors of dengue, yellow fever and chikungunya viruses. Recent estimations suggest a global impact of 390 million dengue infections annually worldwide [1]. Since there are no vaccines or specific treatments for this arboviral infection, the reduction of vector density is one of the most straightforward strategies for its prevention. Furthermore, recent studies unravel the high cost-effectiveness of an active and continuous vector control as opposed to an answer to dengue outbreaks [2]. According to the World Health Organization (WHO), A. aegypti’s control is mainly achieved by source reduction of the vector through the elimination of the mosquito breeding sites [3]. Due to A. aegypti’s domestic ecological feature, their larvae preferably proliferate in small and artificial water-containers, placed inside or near human houses [4]. Therefore, community contribution is, undoubtedly crucial in dengue prevention and control [5, 6]. Educational campaigns that inform and mobilize the local communities are often implemented in the infested areas. In most preventive campaigns, the community is asked to do aegypti-source reduction: to eliminate (cover, empty and/or remove) the most common domestic breeding sites. Abundant literature may be found reporting community-oriented educational interventions and assessments of community knowledge/attitudes/practices/perceptions/beliefs regarding dengue prevention, most of which are performed in tropical regions [7–14]. Even though the relevance of the latter issues is more and more recalled by important entities [15, 16], most of the studies emphasize the need of new research approaches to explain and increase their commonly low efficacy [11–14, 17, 18]. Consequently, studies that suggest and/or test strategies that more effectively promote community behaviours and more accurately assess community perception, are of great need [19]. The ‘community perception’ term used here means “the collective views of a group of people (…) [perception] involves understanding/misunderstanding and discernment, and it includes a choice and action (…) [perception is also] the product of social interaction”, as stated by WHO [19].

In the past years, several viruses and vectors have significantly increased their geographic distribution as a result of globalization [20, 21]. In 2005, A. aegypti specimens were recorded for the first time in Madeira, a temperate European island in the Atlantic [22]. Rapidly, the local health authorities promoted educational activities based on television/radio communications, informative flyers/posters distribution and ‘door-to-door’ interventions to achieve community compliance in the domestic control of A. aegypti [23]. In fact, despite these efforts, the mosquito population has thrived. Additionally, entomological studies reported high levels of resistance to DDT and pyrethroids in the local A. aegypti population [24].

In October 2012, less than one year after the beginning of this study, an outbreak of dengue was declared in the Island [25]. Currently, Madeira is at risk of becoming a dengue endemic territory. Also, being a highly touristic destination, it constitutes an open door for A. aegypti and/or dengue virus introduction into other temperate regions [26]. Moreover, non-tropical regions such as Europe and North America host Aedes albopictus another very competent arboviral vector [27–29]. A unique virus introduction into these temperate regions could trigger a disease epidemic [30]. Community-mobilization strategies that effectively reduce A. aegypti’s densities in Madeira Island are thus, mandatory.

This study aims to estimate the community’s perceptions of Madeira residents regarding source reduction, and identify the most frequent aegypti-breeding sites present in the domestic environment of this non-tropical region. An extensive and in-depth analysis is suggested as a novel tool for community perception assessment and educational planning.

Comparing to other studies, analysis of single concept frequency revealed an (apparent) very good community knowledge [12, 13]. For example, almost 80% of the population recognized that “the source reduction is an effective measure for domestic aegypti-control” (Control Measure 1). However, perception evaluation based on EP-score showed that several essential concepts are still unknown by the majority of the population. Regarding topics understanding, only a few respondents completely understood each of the five topics. In all of them, a great discrepancy was found within the knowledge shown in concepts covering the same topic, predicting the presence of alleged myths/erroneous perceptions in most of the AEGYPTI-population. As suggested in Additional file 3, the dissemination of part of the information can promote the advent of myths. To notice, through an anthropological view these myths are considered the real perception of the community [33]. They are here called ‘erroneous perceptions or myths’ since they oppose and contradict what, to date, is considered to be the main community vector-control practice. Sequential educational activities should take into account those myths given that they could be much harder to amend than the lack of awareness itself.

Four socio-demographic determinants were described in the logistic regression results. Similarly to other studies, the education level was the most relevant determinant in the EP-Score level above 7, emphasizing the relevance of extensive health education programs to improve the health-literacy levels [34–37]. The ‘bitten by mosquitoes’ variable (stating the recognition of having been bitten by mosquitoes) also showed to be a determinant in the level of EP-Score. These suggests that measures that make the problem more ‘visible’ would be of a great impact in community awareness, especially for those who lack the allergic reaction to the bite. Determinants such as, ‘Gender’, and ‘Municipality’ should be considered in the selection of target groups/areas for further campaigns.

Concerning the entomological survey, only putative breeding sites were inventoried. Due to the un-expected absence of rainfall during the period of the study (carried-out during the beginning of the rainy season), most of the containers were dry (Additional file 8). Nevertheless, this was, to our knowledge, the sole entomological survey in a temperate region describing the most common A. aegypti’s domestic breeding sites. The most inventoried putative breeding sites were housing-components present in any patio, balcony or garden areas. An aegypti-infestation pattern was observed compatible with a clean, organized and well maintained urban environment (as schematized in Additional file 9). These results contrast with the common symbols of mosquito infestation in dengue endemic regions, often related to water supply and waste disposal (tires, water tanks, etc.) [38–40]. ‘Santa Luzia”s municipality showed a significantly higher percentage of houses without breeding sites compared to the other two municipalities. This could be explained by a higher conscience of the A. aegypti’s presence in ‘Santa Luzia’ since it was where this mosquito first appeared.

Associations found between EP-Score and presence of domestic breeding sites supported the established criteria (Tables 3 and 4). The important and most acknowledged concepts: DA2 and CM1, per se did not correlate with the absence of breeding sites. Yet, the EP-score level is significantly higher in respondents living in households without putative breeding sites (Table 1). These results seem to support that essential-concepts’ cumulative assimilation is needed for triggering the adoption of the aimed behaviour. Moreover, results from the Incomplete Scores revealed that none of the five topics were dispensable in the improvement of the source reduction compliance. Evidence was provided to use the EP-Score analysis as an accurate tool for perception estimation. Furthermore, comparing to the alternative simple analysis of frequencies (see Table 3), this tool provides deeper and more precise results to explore the community involvement. Actually, the major limitation of knowledge/perception assessments is the lack of its correlation with the adoption of proposed practices, frequently observed in similar studies (most commonly, knowledge-attitudes-and-practices surveys) [10, 14, 15, 34–36, 41]. Methodologies that estimate awareness based on a score were already used in other surveys [13, 14]. However, these approaches rarely or never focus on a specific behaviour, and almost never test understanding discrepancies. Since the adoption of different dengue-related practices (preventing, protecting, diagnosing, treatment-seeking practices, etc.) implicates the understanding of distinct concepts, behaviour-oriented approaches are much more useful to prioritize health-messages and plan campaigns [41]. Analysis of discrepancies in the understanding has been suggested as a way to improve reliability in KAP surveys [17]. Similar studies are now needed to confirm whether this approach is indeed more accurate to assess perceptions and more effective to promote behaviours in the community.

After seven years of coexistence with the A. aegypti, Madeira Island presents an atypical scenario of domestic infestation. Subsequent to several local educational activities, AEGYPTI-community perceptions regarding source reduction were not only insufficient, but also, inconsistent and possibly incorrect. Findings of this study provide crucial guidelines for future educational activities. By addressing the less acknowledged essential concepts and the alleged myths, and by emphasizing the most frequent breeding sites, health messages adapt their content and their focus to more likely help the community in fully engaging in the proposed behaviour. However, after the experience of a dengue outbreak (2012), local population has probably altered their perception, namely in what concerns the topic ‘Local Risk’. Moreover, since, no hemorrhagic clinical cases were detected in the latter outbreak, the real ‘Medical Importance’ of dengue could be still underestimated. These ideas should also be considered by those planning further educational activities on the island. As part of future actions the implementation of another questionnaire, similar to the one carried-out in this study, should be encouraged. In reality, with its recent dengue event, Madeira Island presents an exceptional opportunity to understand the effect of a disease-outbreak in a community’s awareness. Finally, findings of this study support the use of EP-Score methodology as a more efficient tool to evaluate the community-perception regarding a specific behaviour. When further tested, this type of tool will probably prove to be of great value for other health problems, far beyond dengue prevention.