Identification of risk factors affecting transmission of dengue in the District of Gampaha, Sri Lanka

Abstract

INTRODUCTION: Dengue is the most significant mosquito-borne infectious disease in Sri Lanka, causing more than 35,000 cases annually for last five years. The second highest prevalence of dengue was reported from the District of Gampaha for last 10 years. OBJECTIVE: To identify possible risk factors affecting transmission of dengue in selected high risk areas of dengue in the Gampha District. METHODOLOGY: The study was conducted in four high risk Medical Officer of Health (MOH) areas where the annual number of dengue cases greater than 250 during last ten years. In each MOH area, one Grama Niladhari (GN) division with the highest dengue incidence was selected as study areas. In each study area, a cluster of 150, including house-holds, open areas (barren lands, dump yards, and construction sites), abandoned houses, and religious facilities, was selected. A house-hold and entomological surveys were performed in March, 2015 after obtaining an informed written consent. RESULTS: The selected study areas were Akbar town (Mahara MOH), Eriyawatiya (Kelaniya MOH), Kurana (Negombo MOH), and Welikadamulla (Wattala MOH). The size of study human population was 2,544 in 574 house-holds in the study areas and 53.66% (1,365/2,544) were females. The average size of a homestead was 19.3 perches and more than one house was observed in 21.6% (124/574) of land plots. The type of the house-hold was mostly moderate (67.2%-386/574) and the gender of the house-hold head was male in 77.7% (446/574) house-holds. The average number of dwellers in a house-hold was 4 and 7.35% (187/2,544) of the population has previously infected with dengue. Most of house-holds were individual houses with a small garden (98.9%-568/574) and residential function of the house-hold was mainly residential only (83.4%-479/574). The main source of water was piped water (95.1%-546/574), but 39.5% (227/574) using ground-well or tube-well water daily purposes other than drinking and food processing. The most common mosquito preventive measure was bed nets (31.7%-182/574) and 47.6% (273/574) house-holds were using more than one mosquito preventive measures. Collecting tailors of municipal councils is the main solid waste disposal method, while 16.0% (92/574) using burning, burring in pits, composting or open ground due to lack of proper solid waste collection system. Bushes and small trees were the most common vegetation cover of the homesteads (84.5%-485/574) and potential breeding sites were observed in 97.5% (585/600) premises in the study areas. Main mosquito breeding places were plastic and polythene wares, discarded cans and tins, discarded tyres, plant axils, and aluminum and clay pots. The Breteau Index (BI) for Aedes larvae was 4.88 (28/574). Most prominent adult mosquito species in the areas was Aedes albopictus (92.4%-281/304). Dwellers in the study areas have considerable knowledge of the disease and preventive measures, but they reluctant to pursue preventive measures. DISCUSSION: Possible risk factors for transmission of dengue may be crowded conditions, small house-holds and homesteads, poor water and waste management systems, disfavor to pursue preventive measures, and dependence on government vector control programs. Therefore, immense persuade will be required to control dengue in the areas.