SURVEILLANCE AND MANAGEMENT OF MOSQUITO SPECIES WITH SPECIAL EMPHASIS ON THE DENGUE VECTOR(S) IN PESHAWAR VALLEY

Abstract

The present study was planned to investigate the population dynamics and habitats of economically important mosquito species with special emphasis on Aedes spp., the dengue vector in Peshawar Valley during 2011 - 2012. Data were collected from different habitat types in Peshawar, Nowshera, Mardan and Charsadda. Efficacy of different synthetic and natural insecticides as well as IGRs was tested in various concentrations against the mosquito species. In the irradiation experiments various doses of Cobalt 60 were tested to determine the optimum dose for causing male sterility in Aedes albopictus. The result revealed that population of Culex spp. was highest in Peshawar and lowest in Charsadda. The mean abundance of Aedes albopictus was highest in Mardan and lowest in Charsadda. Culex spp. populations peaked during September- October while Aedes spp. during October-November. Highest mean abundance (5300) of the specimen was found in sewage water and lowest in flower pots (11). At all the tested sites sewage water was found more favorable for breeding of Culex spp. while, irrigation channels, scrap, water tanks and pot vases for Aedes spp. The ovitrap index revealed higher population of Culex spp. in the indoor while that of Aedes spp. in the outdoor location. The indoor ovitrap index of Culex spp. was highest in Mardan (16.05%) and lowest in Peshawar (9.38%). The outdoor ovitrap index of Aedes spp. was highest in Nowshera (19.3%) and lowest in Charsadda (7.83%). The vector control In Vitro experiments showed significant differences in larval and adult mortalities as affected by the different synthetic insecticides, IGRs and plant extracts tested in various concentrations. Spatial variation in the mortality of both larvae and adults were observed in response to the insecticides. This variable response might be due to the intra-specie genetic variations from selection pressure of insecticides resulting into the development of resistance in the mosquitoes. The IGRs exhibited LC50 and LC90 in range of 0.002 to 0.016 ppm and 0.008 to 0.115 ppm, respectively. The IGRs yielded significant inhibition (79 to 99.5%) in adult emergence in the 3rd instars larvae of both Aedes and Culex spp. The IGRs were classified in terms of the tested parameters in order of Pyriproxyfen 1.0 WDG > Pyriproxyfen 0.5 WDG > Methoprene. In the field experiments, Pyriproxyfen 1.0 WDG @ 0.1g/m3 resulted in negligible adult emergence over a period of six months in water samples from different treated habitats. Crude plant extracts were tested for larvicidal activity against 3rd and 4th instars of Culex and Aedes spp. Parthenium showed lowest LC50 (0.849-1.543%), LC90 (1.875-2.882%) while Stevia extract the highest LC50 (2.086-2.889%), LC90 (5.836-8.533%) against the 3rd and 4th instar larvae of both the species after 24-48 hrs exposure periods. The larvicidal efficiency of plant extracts were ranked in order of Parthenium > Neem extract > Chrysanthemum > Neem oil > Stevia extract. The results of SIT experiments with Aedes albopictus revealed irradiation dose of 40-60 Gy as optimum for acceptable number of mating (7-8) of sterile males with wild female, negligible fecundity and subsequent hatching in no choice tests.