DDT-Modulated Behavioural Profile in Terms of Longevity, Fecundity Fertility and Fitness in Subsequent Generations of DDT-resistant Phlebotomus argentipes (Diptera: Psychodidae)

Dichlorodiphenyltrichloroethane (DDT), a chlorinated insecticide served as a well-established tool against the Indian Visceral leishmaniasis (VL) or kala-azar vector, i.e. Phlebotomus argentipes (Diptera: Psychodidae) till infestation with insecticide resistance (IR) among these vector species, leading to the legacy of failure of major campaigns for global VL elimination via vector control strategy. Failing in the task of controlling the insect population, IR has definitely imposed a negative impact over the quality of mosquito vector species in terms of their physiological fitness and reproductive viability, but this has never been reported in the case of Indian VL vector. Therefore, to explore IR implications and comparative assessment over the physiological fitness and reproductive robustness within subsequent generations of laboratory- reared resistant sand flies, bioassay experiments have been performed up till the seventh generation of homozygous 4% DDT-resistant strained colony (DRC) of P. argentipes. With observed mean vector longevity ranging between 3 and 9 days (for male sand flies) as well as 5 and 13.5 days (for female sand flies) till their seventh generation, IR causes an abrupt decrease in fecundity (with mean potential fecundity per female from 60.72 to 6.44), fertility (with mean no. of eggs oviposited per female from 53.4 to 6.02 and mean no. of eggs hatching per female from 13.6 to 1.67) and greatly affecting reproductive fitness and behaviour throughout the studied generations of DRC sand flies. The affected DDT-modulated behavioural profile in terms of the studied four-pronged LF3 parameters (i.e. longevity, fitness, fecundity and fertility), revealed that the changed quality of DRC P. argentipes in the forthcoming generations to such an extent, that it might prove to be detrimental to the survival and fitness of the sand flies, if selection pressures maintained throughout their subsequent generations. The results of the present study provide the probable reasons and side effects associated with the developed resistance both at macroscopic and microscopic levels, which deserve additional attention for upischolar_maining the disease from its end.