Evaluation of insecticidal resistance in mosquitoes under controlled conditions.

Abstract

On an overall basis, fifteen species were recorded from four selected districts during 2016-17. However, populated area proved to more infested followed by agricultural and industrial area. Rawalpindi depicted as more diversified district as compared to Lahore, Sialkot and Faisalabad. A huge number of insecticides are used for the control of agricultural pests and household pests, such as mosquitoes, with the application of over and under doses in Punjab, Pakistan. Moreover, after the dengue epidemic that occurred during 2010, insecticides were sprayed in huge amounts and at high doses in major cities of Punjab to control mosquitoes. This also resulted in insecticidal resistance in mosquitoes. Mosquitocidal assays of larvae (in beakers) and adults (impregnated papers) were evaluated after 24 h. The bioassay data showed Temephos, Fenitrothion, Malathion, Pirimiphos Methyl, Cypermethrin, Deltamethrin, Permethrin and Bendiocarb lethal concentration (LC50) for 50 percent mortality of Ae. aegypti, Cx. quinquefasciatus and An. Stephensi susceptible population (SS) compared with field populations of Faisalabad (FSD), Sialkot (SKT), Rawalpindi (RWP) and Lahore (LHR). The larvicidal LC50 value of temephos ranged from 0.007 to 0.416 ppm. In the case of adulticides, three groups of insecticides were applied to papers and used against different populations collected from populated, agricultural and industrial areas of Lahore (LHR), Rawalpindi (RWP), Sialkot (SKT) and Faisalabad (FSD). Pyrethroids demonstrated the lowest effective concentration among the tested pesticides (organophosphates & carbamates). Among the pyrethroid group, deltamethrin was recorded as being the most toxic (0.483 – 9.245 ppm), followed by cypermethrin (1.839 – 33.139 ppm) and permethrin (5.145 – 101.533 ppm). ppm. The chi-squared value showed no heterogeneity across all the experiments. The results also indicated that the LHR population was highly resistant, followed by the RWP, SKT and FSD populations; moreover, the mosquito populations from agricultural areas were more resistant than those from populated and industrial areas. However, the resistance map also reflected that LHR showed extremely high to high level resistance which was indicated by red to blue color whereas RWP found high to moderate resistance indicated by blue to yellow followed by SKT and FSD. The biochemical analysis showed the elevated activity of enzymes (esterases, mixed-function oxidases, glutathione S-transferase and acetyl-cholinesterase) in resistant populations. It was concluded that the injudicious application of chemicals in an area caused the risk of resistance and the reappearance and resurgence of certain mosquitoes. Further, research is needed to identify health and environmental risks and to devise an effective programme through the use of selective and specific insecticides.