Risk of infection of Wuchereria bancrofti to humans by Culex quinquefasciatus in Pondicherry and its relationship with microfilaria prevalence

The risk of infection (RI) with Wuchereria bancrofti by vector mosquitoes has been conventionally estimated from the biting population of all age classes. This estimate of RI had no correlation with microfilaria (mf) prevalence and intensity of infection in humans. A new method for estimating RI from a resting population of Culex quinquefasciatus is proposed based on a longitudinal study in seventeen sites in Pondicherry, India. Unlike previous estimates, RI calculated by the present method considering the density of parous mosquitoes collected per man-hour and the mean number of infective stage larvae per parous mosquito significantly correlated with mf prevalence in humans during both early ( r = 0.559; P = 0.038) and late in the control operation ( r = 0.572; P = 0.033). RI varied significantly between the early and late in the control operation and different sites. On average, RI was reduced significantly during the control operation. Further epidemiological implications are discussed.