Irregular water supply, household usage and dengue: a bio-social study in the Brazilian Northeast Abastecimento irregular de água, seu uso domiciliar e dengue: uma pesquisa biossocial no Nordeste do Brasil

Despite increased vector control efforts, dengue fever remains endemic in Fortaleza, Northeast Brazil, where sporadic epidemic outbreaks have occurred since 1986. Multiple factors affect vector ecology such as social policy, migration, urbanization, city water supply, garbage disposal and housing conditions, as well as community level understanding of the disease and related practices. This descriptive study used a multi-disciplinary approach that bridged anthropology and entomology. A multiple case study design was adopted to include research in six study areas, defined as blocks. The water supply is irregular in households from both under-privileged and privileged areas, however, clear differences exist. In the more privileged blocks, several homes are not connected to the public water system, but have a well and pump system and therefore irregularity of supply does not affect them. In households from under-privileged blocks, where the water supply is irregular, the frequent use of water containers such as water tanks, cisterns, barrels and pots, creates environmental conditions with a greater number of breeding areas. In under-privileged homes, there are more possible breeding areas and environmental conditions that may improve the chances of Aedes aegypti survival. Dengue; Water Supply; Anthropology; Entomology Introduction Fortaleza, the capital city of Ceará State in Northeastern Brazil, is a peculiar urban context for dengue fever transmission. It has 2.2 million inhabitants and is one of the largest Brazilian metropolises, ranking fourth among the most populated cities in the country. The city is also ranked as one of the urban areas with high-income concentration, and huge differences exist between its poorest and richest residents 1. Fortaleza is located in a hot, semi-arid region with an average annual rainfall of 1,200mm, compared with 400mm in the interior of the state. Dengue fever has been endemic since 1986, with important outbreaks in 1987 (378/100,000), 1990 (232/100,000), 1994 (732/100,000), and 2001 (456/100,000). In 2006, 172 hemorrhagic dengue fever cases were notified, along with 15 deaths 2. After the 1994 epidemics, a survey revealed a seroprevalence of 45% 3 in urban residents. In another Brazilian city, Salvador in Bahia State, the seroconversion found to be 70.6% in 2001 4. These data support the assumption that there is a high proportion of infected individuals in large cities in the Northeast of Brazil, with an accompanying elevated risk of epidemic dengue hemorrhagic fever. There is a general lack of knowledge about the dynamics of community practices, state-based disease control, vector ecology and the wider political economic context 5,6,7. Such knowledge is needed to develop more effective dengue conARTIGO ARTICLE Caprara A et al. S126 Cad. Saúde Pública, Rio de Janeiro, 25 Sup 1:S125-S136, 2009 trol strategies. The framework shown in Figure 1 illustrates the complexity of the social, political and ecological determinants affecting dengue fever incidence in Fortaleza. It is not intended to be exhaustive; rather, it highlights factors that are hypothesized to play a role in dengue persistence in the face of intensified control measures. Three main domains make up the first organizational level: eco-biological, political-economic and social. The eco-biological domain encompasses elements such as vector ecology and biology, climate (temperature, rainfall); the politicaleconomic sphere includes, among other factors, social policy, migration, urbanization, city water supply, and garbage disposal; and the social level includes housing, basic sanitation, water supply and understandings and practices among the population 8. A bio-social approach was adopted to identify both the biological and socio-behavioural factors 9,10,11,12,13 that have contributed towards the re-emergence of dengue fever including: poor housing and basic sanitation, lack of adequate water supply, the use of unprotected reservoirs for potable water, and no public garbage collection 14. The study addresses the complexity of dengue fever emergence, in order to identify appropriate control strategies based on meaningful community involvement 15. From the bio-ecological perspective, the presence of the vector mosquito Aedes aegypti, and the quantity of breeding sites are the most important factors of Dengue occurrence 15. Domestic water storage containers are breeding sites for Ae. aegypti 16. In 2001, there were 278,000 potable water containers in Fortaleza. Many of them are still not protected from mosquito access. Studies focusing on prevention suggest considering housing conditions, social cohesion and risk perception, as well as community interpretations and practices affecting vector ecology 15. Housing conditions are linked with water supply and storage, garbage disposal and consequently with the presence of breeding sites 17.