Global water quality changes posing threat of increasing infectious diseases, a case study on malaria vector...

Water pollution due to uncontrolled release of chemical pollutants is an important global problem. Its effect on medically important insects, especially mosquitoes, is a critical issue in the epidemiology of mosquito-borne diseases.

In order to understand the effect of water pollutants on the demography of Anopheles stephensi, colonies were reared in clean, moderately and highly polluted water for three consecutive generations at 27 °C, 75% RH, and a photoperiod of 12:12 h (L:D). The demographic data of the 4th generation of An. stephensi were collected and analysed using the age-stage, two-sex life table.

The intrinsic rate of increase (r), finite rate of increase (λ), mean fecundity (F) and net reproductive rate (R₀) of An. stephensi in clean water were 0.2568 d^-1, 1.2927 d^-1, 251.72 eggs, and 109.08 offspring, respectively. These values were significantly higher than those obtained in moderately polluted water (r = 0.2302 d^-1, λ = 1.2589 d^-1, 196.04 eggs, and R₀ = 65.35 offspring) and highly polluted water (r = 0.2282 d^-1, λ = 1.2564 d^-1, 182.45 eggs, and R₀ = 62.03 offspring). Female adult longevity in moderately polluted (9.38 days) and highly polluted water (9.88 days) were significantly shorter than those reared in clean water (12.43 days), while no significant difference in the male adult longevity was observed among treatments.

The results of this study showed that An. stephensi can partially adapt to water pollution and this may be sufficient to extend the range of mosquito-borne diseases.