Knowledge and practices related to dengue and its vector: a community-based study from Southeast Brazil

Abstract

INTRODUCTION:   This study investigated the knowledge of users of primary healthcare services living in Ribeirão Preto, Brazil, about dengue and its vector.

METHODS:  A cross-sectional survey of 605 people was conducted following a major dengue outbreak in 2013.

RESULTS:   Participants with higher levels of education were more likely to identify correctly the vector of the disease.

CONCLUSIONS:   The results emphasize the relevance of health education programs, the continuous promotion of educational campaigns in the media, the role of the television as a source of information, and the importance of motivating the population to control the vector.

Keywords: Knowledge; Attitude; Dengue vector

Vector control, the most important strategy to prevent and control dengue, requires the cooperation of entire communities, as it is not solely a government responsibility. Communities should be educated about eliminating the potential for breeding and other prevention strategies, which requires an understanding of their knowledge and practices concerning dengue. There is a gap between knowledge and attitudes about dengue in various Brazilian regions^{1) (2}. Thus, this cross-sectional study investigated the knowledge of adults who are users of primary healthcare services of Ribeirão Preto, in Southeast Brazil, about dengue and its vector (transmission, symptoms, prevention, and treatment), and their source of the information and health practices.

The municipality of Ribeirão Preto, is divided into five health districts, consisting of 41 primary healthcare units with diverse demographic characteristics³. For sampling purposes, the healthcare units were classified using the São Paulo Social Vulnerability Index [Índice Paulista de Vulnerabilidade Social (IPVS)], based on their predominant areas of coverage. The IPVS, proposed by the State Data Analysis System Foundation, classifies geographical areas into six categories of social vulnerability. Thus, the units were grouped by health district and IPVS classification to form 10 strata. One unit was randomly selected from each stratum for the interviews. The minimum sample size of 605 individuals was determined using a stratified sampling design, a confidence coefficient of 0.95, and an absolute precision of 0.04 for the proportion of individuals with satisfactory knowledge about dengue control. In 2008, 52% of the municipality's urban population had exclusive use of the public healthcare resources and 80% used these services at some time³. Thus, this study's sample of 605 participants is considered representative of the municipality's population.

Individuals were invited to participate in the study while they waited for medical care in the health units. A poster created using colorful images obtained from the Internet of the Aedes aegypti mosquito and seven other insects (Rodnius prolixus, Angarotipula sp., Anopheles gambiae, Palexorista sp., Polistes metricus, Tabanus sp., and Culex sp.), was used to assess participants' ability to identify the dengue vector. Aedes albopictus, first reported in São Paulo State in September 1986⁴, was not included because its vector competence for dengue viruses in Brazil remains uncertain⁵.

Data were collected from July 2013 to September 2014, following a major dengue outbreak. All data were collected before the first autochthonous transmission of the chikungunya virus in Brazil that was detected in September 2014⁶. Thus, there was no possibility of confusion between the two different diseases. The proportions of respondents who correctly identified the dengue vector were analyzed using the general linear model and SAS software version 9.3.

The respondents' characteristics are presented in Table 1. The disproportionate number of women in the study was consistent with gender differences in the use of primary healthcare services in Brazil⁷. The percentage of respondents claiming to have dengue previously (26.9%) is imprecise because dengue may easily be confused with other causes of fever, its clinical manifestations are not always present⁸, and not all suspected cases are laboratory confirmed during epidemics⁹. Most of the respondents did not correctly identify the time of day that mosquitos bite (Table 2). More than half reported that mosquitoes bite at any time. This belief is not entirely wrong because although their activity is predominantly diurnal¹⁰, mosquitoes bite at any time if there is enough ambient light. However, accurate knowledge of the Aedes' biting habits is important, as mosquito repellents will be ineffective if used at night. Among the 11 respondents who believed that dengue is transmitted through standing water, three completed secondary education, five completed primary education, and three had not completed primary education. A large number of respondents did not know the number of times a person could have dengue fever; only 3.5% responded that it was four times.

Table 1:
Participants' demographic characteristics and their knowledge and attitudes about dengue.

• *Respondents were allowed to choose more than one answer.

Table 2:
Participants' knowledge of dengue and their perceptions of the risk of becoming infected with dengue.

Television was the main source of information about dengue (87.8%), followed by pamphlets/posters (41.8%), internet (17.5%), hospitals and health units (17.4%), radio (12.2%), newspapers (9.7%), children's schools (5.6%), friends (4.6%), relatives (4.3%), schools, colleges, or faculty (4%), and church or religious groups (2.2%). The percentage of respondents who cited the internet as an information source ranged from 0% (illiterate) to 45.6% (university-educated). During data collection, several of the educational pamphlets/posters in the health units were found to represent the mosquito in a very stylized and often humanized form, with wicked facial expressions, similar to cartoon characters, as if dengue transmission is a rational act. Exposure to these metaphors could have adversely affected respondents' ability to identify realistic pictures of the vector and their understanding of the dynamics of disease transmission.

When asked to list dengue symptoms, most (79.7%) participants listed fever, which is similar to other studies^{11) (12) (13}. This result was probably due to educational messages in the mass media, citing fever as dengue's primary symptom¹¹. The recognition of dengue symptoms is crucial for early treatment¹³. Other symptoms reported by participants in descending order of frequency were muscular pain (66.6%), headache (65.1%), redness of the skin (36%), pain behind the eyes (26.1%), fatigue (20.8%), joint pain (17.4%), vomiting (16.2%), diarrhea (15%), malaise (5.8%), itch (5.1%), nausea (4.5%), loss of appetite (4.3%), dizziness (1.5%), and weakness (1.2%).

Only 10.4% of respondents used mosquito repellent regularly; fewer used homemade repellents (e.g., citronella oil and alcohol with Indian clove). The proportion of respondents who used repellent regularly showed a gradual increase with educational level, ranging from 7.1% among the illiterate respondents to 21.1% among the respondents with a university education.

Participants' answers to an open-ended question about ways to prevent dengue revealed that only 8.8% believed that avoiding dengue was impossible or did not know how to avoid it. Other methods included not allowing standing water to accumulate (67.4%), maintaining hygiene and cleanliness in the environment (21.3%), preventing mosquito proliferation (9.4%), increasing public awareness and knowledge (8.1%), not leaving potential breeding environments exposed (tires, buckets, water tanks, and water drains) (7.3%), cooperating with local governments and health surveillance, encouraging public investments in sanitation services (3.5%), and following the instructions of health surveillance or community-based health workers e.g., allowing home inspections (0.7%).

In response to an open-ended question about what participants actually did to prevent dengue, 9.9% believed it was possible to avoid dengue, but did nothing to prevent it. The most frequent answers were avoiding the accumulation of standing water (44.3%) and keeping the house and/or yard clean (23%).

When respondents were shown the poster to identify the insects responsible for dengue fever transmission, 3.5% said they did not know. The remaining respondents identified more than one insect; 69.3% correctly identified Aedes aegypti, 12.1% indicated Angarotipula sp. (a cranefly), 8.3% chose Culex sp., and 6.1% indicated Anopheles gambiae. Two respondents selected Rodnius prolixus, two chose the fly, Palexorista sp. and the wasp, Polistes metricus, while three respondents answered that none of the insects on the poster transmit dengue.

The correct identification of the dengue vector varied with respondents' age and education (Table 3). The proportion of correct identifications decreased from 84% among the respondents under 25 years of age to 46.8% among those above 60 years of age. Higher educational level and internet access increased the likelihood of identifying the vector, with a proportion ratio (PR) of 1.44 [95% confidence interval (95% CI): 1.07-1.64] compared to those without internet access. This finding was still significant when the model was adjusted for age (PR = 1.24, 95% CI: 1.07-1.44) or educational level (PR = 1.27, 95% CI: 95%: 1.10-1.47). The proportion of correct identifications of the vector was significantly higher among respondents who used mosquito repellent sometimes or regularly, and the results remained significant after adjusting for age or educational level.

Table 3:
Characteristics of the respondents who correctly identified the dengue vector.

• 95% CI: confidence interval; CI that does not include the value 1 are marked with an asterisk and they indicate significant differences at 0.05 level.

This study's limitation is that the results cannot be generalized to a broader population. However, they are similar to those of other studies^{1) (2) (11) (12) (13}, and they reinforce the relevance of health education programs, the continuous promotion of educational campaigns in the media, the role of television as a source of information, and the importance of motivating people to control the vector.

Recently, a phase 3 efficacy trial showed that a tetravalent dengue vaccine was efficacious against virologically confirmed dengue¹⁴, which brings new hope for control of the disease. However, efforts must continue to improve mosquito control, given the likely rise of other arboviruses transmitted by Aedes mosquitoes, such as the Zika virus infection, identified the first time in Brazil in 2015¹⁵, and Chikungunya fever, first detected in Brazil in 2014⁶.

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• This work has received financial support by National Counsel of Technological and Scientific Development [Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)] (Process 305942/2012-3)

Publication Dates

• Publication in this collection
  Mar-Apr 2016

History

• Received
  14 July 2015
• Accepted
  23 Sept 2015