Impact of long-lasting insecticidal nets on resting and feeding behaviour of Anopheles fluviatilis and Anopheles culicifacies (Diptera: Culicidae), the vectors of malaria in East- Central India

Abstract

Abstract Background & Objectives: Currently, the malaria control strategies in Odisha to achieve the goal of malaria elimination rely on long-lasing insecticidal nets. Shifting of behaviour in anopheline vectors poses a significant challenge for elimination of malaria. This manuscript discusses the shift in the behaviour of two primary vectors of malaria; Anopheles fluviatilis James s. l. and Anopheles culicifacies Giles s. l. after universal coverage of LLINs in Odisha State during 2017. Methods: Mosquito collections were made fortnightly from the selected villages of Koraput and Malkangiri districts of Odisha State from April 2019 to March 2021. The entomological parameters; density, parity, sibling species composition, infection and human blood index of two malaria vectors and epidemiological parameters such as malaria incidence were assessed. Results: The PMD of An. fluviatilis was zero in human dwellings in both the districts and the average PMD in cattle sheds was 1.5 in Koraput and 0.01 in Malkangiri district. In Koraput district, the average PMD of An. culicifacies was zero in human dwellings and 7.0 in cattle sheds and the corresponding values in Malkangiri district was 2.2 and 10.1, respectively. The foot-hill and plain ecotypes had a significantly greater abundance of An. fluviatilis and An. culicifacies, respectively. While winter season was the favourable period for the abundance of An. fluviatilis, both summer and rainy seasons are favourable period for An. culicifacies. The HBI of An. fluviatilis and An. culicifacies was 0.01 and 0.007, respectively. Discussion: A shift in the resting behaviour of An. fluviatilis from human dwellings to cattle sheds and feeding behaviour from anthropophagy to zoophagy, change in sibling species composition from species S to T and reduction of vector infection status to zero was observed in this study. None was found positive for malaria in the study villages. Conclusion: The study highlighted the necessity of continuing the ongoing vector control tool, i.e. LLINs for effective control of malaria.