Trend of mosquito larval indices over a year in a rural area of Thrissur district, Kerala

Abstract

Background: Dengue is the most widely distributed viral disease in the world. Outbreak are usually seasonal, peaking during and after rainy seasons. Entomological surveillance is important in determining the factors related to disease transmission in order to prioritize areas and seasons for vector control. The objectives of the study were to determine the larval indices of aedes, assess the seasonal trend in larval indices and determine the major breeding site of Aedes mosquitoes. Methods: A longitudinal study was conducted over a period of 12 months from January to December in Thrikkur panchayath area. From the total of seventeen wards, 4 wards are randomly selected and from these, 75 houses are randomly selected. Results: From the surveyed houses 959 wet containers were examined of these 180 were found positive. Wet containers, positive containers and positive houses were more identified during rainy season. The most common site for vector breeding as per the survey was identified to be plastic containers. Aedes was the major species identified. Since the breteau index is between 5 -50, the area studied is considered as moderate risk for epidemics. Conclusions: Results of the study indicated that the vector indices were more during monsoon period. So, control measures need to be adopted with much vigour even during the pre-monsoon and need to continue during the monsoon season also. Plastic containers were a major source of vector breeding and Aedes was the commonest species identified.