BIOECOLOGY AND CHEMICAL CONTROL OF AEDES MOSQUITOES IN DHAKA CITY

Abstract

A comprehensive research was conducted during January, 2013 to December, 2015 to study the life history traits through the life cycle of the medically important mosquitoes Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse,1894) and their breeding sites, seasonal distribution affecting occuarence of dengue disease in different areas of Dhaka city and chemical control approach. The period of development from the egg to adult stage for aedes mosquitoes was 8.37±0.18 days for male and 9.5± 0.24 days for female. Female aedes mosquitoes fed with c h i k e n blood showed the highest mean longivity which was 26.23±2.17days while 10% sucrose fed male recorded 19.23±2.21days which was the shortest mean survival period. Depending on the gonotrophic cycle of aedes mosquitoes their number of eggs and longevity varied.This research investigated aedes mosquito container productivity of each type and identified breeding sites of aedes larvae. Of total 9,222 households inspected, 1,306 (14.2%) were positive for aedes larvae breeding. Out of total 38,777 wet containers examined in the houses, 2,272 (5.8%) were infested with aedes larvae. Water holding containers, such as tyres, tanks, earthen jars, flower pots and drums were found to be the most common containers for aedes mosquitoes breeding. Tyres in outdoor, tanks in indoor and flower pots in rooftop locations were also important containers for the highest larval breeding. Factors such as independent household, presence of a water storage system in the house, and fully/partly shaded outdoors were found significantly associated with household infestation of aedes larvae. All these containers exhibited risk of breeding aedes mosquitoes. To evaluate ecological variation of their population density in different parts of the Dhaka city among its eight major divisions average highest density of both these mosquitoes at all the life stages viz. eggs, larvae, pupae and adults was in Tejgaon division with 2960±9.82, 2329 ±4.36, 1786.33±35.92 and 1369.67±16.50 respectively and the lowest density of 1556±51.39, 1122.67±32.88, 764±34.39 and 570.67±7.02 in Lalbagh division. The seasonal distribution of the aedes mosquitoes showed that the highest density of eggs, larvae, pupae and adults was found in June respectively following May with their mean numbers of 556±103.94, 451.76±103.42, 356.72±102.06 and 291.44±91.85respectively. The abundance of these mosquitoes was related to prevailing rainfall and temperature in these months. The highest LD 50 value of used petroleum oil as diesel was 12.57 after 6hr following kerosine and the lowest LD 50 value of organophosphorous insecticide as temephos was 1.24 after 24 hr of 1 instar larvae. The efficacy of the the tested insecticides decreased with developing larval instars and the LD 50 values thus increased. The pyrethroid insecticides such as pralemethin, deltamethin and permethrin killed almost at similar level, but their effectiveness appeared to be next to organophosphorous insecticide temephos.