Diarrheal diseases and dengue fever are major global health problems. In areas without a regular, safe water supply, water is frequently stored in containers in and around homes, providing abundant, ideal habitats for dengue vectors to breed. Fecal contamination of stored water used for ingestion is also a source of diarrheal illness. Containers used to intentionally store water may thus be a common denominator for both diseases. Effective control of both diarrheal diseases and dengue depends on the provision of a reliable supply of safe water, appropriate water management practices, and community participation in control efforts [1, 2]. Integrated interventions that target both diseases are likely to be both effective and cost-efficient.
Globally, about 88% of the diarrheal disease burden is due to unsafe water supply and lack of sufficient sanitation and hygiene [1, 3]. An estimated 780 million people lack access to safe water sources and 2.5 billion do not use improved sanitation . Despite these high numbers, substantial improvements have been achieved during the last decades evidenced by 89% of the global population currently using improved drinking water sources and 63% having access to improved sanitation. In fact the target of the Millennium Development Goal to reduce by half the proportion of people without sustainable access to safe drinking water has been met . However, about 4 billion cases of diarrhea still occur annually, killing about 2 million people, primarily children in developing countries [1, 5]. Infections usually arise through ingestion of water contaminated with human or animal feces . Inadequate domestic water supply, for example absent or irregular piped water, forces people to collect water and store it in or near houses. Microbial contamination between source and point-of-use is often a significant cause of reduced water quality .
Dengue fever is the most rapidly spreading vector-borne disease globally. Around 50 million cases, mainly children, occur annually in about 100 countries  and about 2.5 billion people live in risk areas . Dengue, and its more severe manifestation, dengue hemorrhagic fever (DHF), are caused by a flavivirus with four different serotypes. Dengue is transmitted primarily by the Aedes aegypti mosquito, which preferentially breeds in artificial water containers in close proximity to human habitation. Dengue transmission risk increases with rapid, unplanned, and unregulated urban development, poor water storage, and unsatisfactory sanitary conditions [8, 10–13]. As no effective dengue vaccine or therapeutic drugs are available, vector control is the only way to prevent dengue transmission.
Diarrhea and dengue are both highly endemic throughout Latin America and the Caribbean. In 2000, an estimated 71.5 million people lacked access to safe drinking water in this region . In 2000, 76% of Colombian municipalities did not have potable water, and an estimated 60% of the inhabitants in rural areas had a medium to high risk of contracting diseases because of poor water quality . In 2009, 14.4 million people were at high risk of water shortage and only 40% of households had both water connection and sewage . In 20% of Colombian municipalities (222 of 1,102) the water supply coverage in rural areas was <30% and in as many as 54% of all Colombian municipalities the sewage coverage in rural areas was <30% . Region-wide infant mortality rates from diarrheal disease were 3.7% during 2000 to 2005, but in the Andean sub-region, including Colombia, the rate was 7.8% . Diarrhea is a leading cause of morbidity and one of the 10 most important in terms of mortality in Colombia , with an estimated prevalence of 13% in children <5 years old . In 2008, the Pan-American Health Organization (PAHO) reported that Brazil, Venezuela, México, and Colombia had the highest number of dengue cases in the Americas. In Colombia, about 65% of the urban population is considered to be at high risk of contracting dengue. Dengue hemorrhagic fever (DHF) incidence in Colombia constitutes 58.6% of all DHF in the Andean region, and 30% of all DHF in the Americas . All four dengue virus serotypes circulate in Colombia and in addition to Ae. aegypti, a secondary dengue vector, Aedes albopictus, has become established in western Colombia [20, 21]. In Colombia, as in many other countries, the organophosphate larvicide temephos is commonly added to water storage containers as a key component of dengue vector control programs. Although temephos is safe for human consumption , temephos treatment often encounters strong opposition from householders when the water is used for drinking, as it can cause the water to appear cloudy and has a disagreeable taste. Lack of a chemical barrier to mosquito breeding puts drinking water containers at a potentially higher risk of becoming dengue vector breeding sites. Resistance to temephos in Aedes aegypti has been identified in many locations in Colombia, including in the current study area [23–25].
Studies from the Caribbean region indicate that poor provision of reliable drinking water supply and waste disposal services was largely responsible for Ae. aegypti propagation [26, 27]. In Colombia, householders often keep a stored supply of water in the home, even in areas with access to piped water. On this country’s Caribbean coast, household water storage tanks and drums were found responsible for producing up to 95% of Aedes aegypti pupae . These same containers were also shown to be the primary dengue vector breeding sites in studies in Antioquia and Cundinamarca provinces in central Colombia [29, 30]. While the water stored in these containers is often used for washing and cooking, it can also be used for human consumption. Although little published research is available on the epidemiology of diarrheal illness in Colombia, lack of access to reliable, clean drinking water is likely a key factor in making it a leading cause of morbidity, particularly among children.
There is little existing information on the functional relationships between diarrhea and dengue fever. A literature search reveals few studies where risk factors of the two diseases have been studied simultaneously and how one affects the other. Full-text searches of the Cochrane database, Web of ScienceSM, and Pub Med using the search terms ‘dengue’, ‘dengue fever’, ‘diarrhea’, and ‘diarrhoea’ and combinations thereof yielded no relevant studies. As no studies of this kind have been carried out in schools, little is known of how stored water influences the risk of diarrhea and dengue and how interventions against both diseases affect children in school settings.
Our study focuses on schools for two key reasons. First, the morning biting peak of the local dengue vector occurs when children are likely to be in school . If schools are important dengue vector breeding grounds, children attending school may be disproportionately exposed. Second, only about 37% of the schools in the study area have access to potable water , potentially exposing pupils to diarrheal pathogens from water ingested at school.
This study protocol description follows the CONSORT statement extension to cluster randomized trials .
This trial will investigate whether a set of disease-specific interventions will significantly reduce diarrheal cases and dengue entomological risk factors in rural primary schools in two municipalities in Colombia. The hypothesis is that the interventions will significantly reduce the number of diarrheal disease cases, the number of school absence episodes, dengue vector infestation, and water contamination as compared to schools that do not receive the interventions.
Specifically, we hypothesize that the interventions will:
Reduce exposure to diarrhea risk factors in schools by:
improving drinking water quality;
improving hand-washing practices;
improving sanitary hygiene;
improving health education on diarrheal disease prevention.
Reduce exposure to dengue risk factors in schools by:
reducing mosquito entry to school classrooms by insecticide-treated curtains;
reducing dengue mosquito vector breeding through source reduction and larval control;
improving health education on dengue prevention.
Reduce the incidence of diarrheal illness in school children.
Reduce the number of absence episodes and length of those due to these illnesses.