Entomological survey of dengue vector breeding sites in Colombo, Sri Lanka

Introduction: In Sri Lanka, the number of dengue cases has steadily increased in recent years. Prevention through disease and vector surveillance is an important strategy in dengue control. The aim of the study was to assess Aedes mosquito breeding sites and the prevention practices of community members in one heavily urbanized area of Colombo. Methods: A cross-sectional entomological survey was conducted from April to June 2013 in 1469 premises located in a sub-district of Colombo Municipality. Types of breeding sites and infestation with larvae or pupae were recorded and a questionnaire was administered to occupants to assess knowledge and practises concerning dengue vector control. Results: The surveyed premises included 1341 households (91%), 99 work or public sites and 11 schools. 126 premises were positive for Aedes larvae or pupae. 12 672 potential breeding sites susceptible to host larvae or pupae were recorded, of which 21% contained water. Among these, 6% were positive for larvae and 13% for pupae. For schools the percentage rose to 40% and 67%, respectively. The main productive breeding sites were: discarded items, water tanks, ornamental plants, ponds and flowerpots, and non-specified containers. The majority was located on outdoor ground areas. Compared to households, the odds ratio for non-household premises of being infested with larvae was 2.29 (P = 0.005, 95% CI: 1.278–4.129) and with pupae 5.76 (P < 0.001, 95% CI: 2.660–12.497). Occupants of 82% of the premises reported using preventive measures. The main practices were coverage of containers and elimination of mosquito-breeding places. 45% of schools and 19% of households took no preventive measures. There was a significant correlation between the occurrence of preventative measures taken and the type of premise involved (P = 0.002). Conclusion: Residential buildings had the lowest relative number of potential breeding sites, and household members reported a high use of vector control measures. Sc