Physiological and reproductive fitness cost in Aedes aegypti on exposure to toxic xenobiotics in New Delhi, India

Abstract

Aedes aegypti, is a well-known vector of dengue, Chikungunya and Zika at the global level. Primary use of pyrethroids as control interventions has caused the development of a considerable level of immunity in Ae. aegypti. The current study assessed the efficacy of a pyrethroid, ?-cypermethrin on the survival and various life parameters of Ae. aegypti. The larvicidal studies with ?-cypermethrin revealed the respective LC50 and LC90 values as 0.26526 mg/L and 0.60211 mg/L. The impact of LC50 level was assessed on the growth and life attributes; such as gonotrophic cycle, egg development, hatchability, development and survival of immature stages, adult longevity, reproduction rate and generation time; of fourth instar of susceptible (S) and ?-cypermethrin-exposed population (E). The exposed population showed diminished fitness as compared to the susceptible population. The individual female fecundity in susceptible population was recorded as 79.6 with 61.6% hatchability rate as compared to the 28 eggs/female and 25% hatchability in the exposed population. The mean egg hatch time in S strain increased by 2-fold in E strain. The proportion of immature survival observed in S strain was 0.88 for fourth instar to pupa (P/I), 0.94 for pupa to adult (A/P) and an overall 0.83 for fourth larva to adult (A/I), which respectively reduced to 0.32, 0.86 and 0.27 in E strain of Ae. aegypti. Likewise, the net reproductive rate, birth rate and death rate were significantly (p < 0.05) higher in S than in E strain. This study demonstrates the negative impact of ?-cypermethrin on the physiological and reproductive fitness of Ae. aegypti.