The southern districts of Odisha State in east-central India have been highly endemic for falciparum malaria for many decades. However, there is no adequate information on the abundance of the vector species or their bionomics in relation to space and time in these districts. Therefore, a study was carried out on the entomological aspects of malaria transmission to generate such information. Collections of mosquitoes were made once during each of the three seasons in 128 villages selected from eight districts. Villages within the foot-hill ecotype had a significantly greater abundance of Anopheles fluviatilis James s. l., whereas the abundance of Anopheles culicifacies Giles s. l. was significantly greater in the plain ecotype. The abundance of An. fluviatilis was maximum during the cold season, whereas An. culicifacies abundance was highest during summer and rainy seasons. The maximum likelihood estimation of the malaria infection rate in An. fluviatilis was 1.78%, 6.05%, and 2.6% in Ganjam, Kalahandi, and Rayagada districts, respectively. The infection rate of An. culicifacies was 1.39% only in Kandhamal district; infected females were not detected elsewhere. Concurrently, the annual malaria parasite incidence (MPI) was significantly higher in hill-top (17.6) and foot-hill (14.4) villages compared to plain villages (4.1). The districts with more villages in hill-top and foot-hill ecotypes also had a greater abundance of An. fluviatilis, the major malaria vector, and exhibited a higher incidence of malaria than villages within the plain ecotype, where An. culicifacies was the most abundant vector.

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The culture supernatant of a strain of Bacillus subtilis subsp. subtilis isolated from mangrove forests of Andaman and Nicobar islands, India was found to kill larval and pupal stages of mosquitoes. A chloroform extract of the culture supernatant of the bacterium showed pupicidal effects at an LC(50) dose of 1 microg/ml. The mosquitocidal metabolite(s) produced by this strain were purified by gel permeation chromatography. The purified fraction was subjected to Fourier transform infrared (FTIR) spectroscopy and Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. The FTIR spectrum of active fraction/CHCl3 residue showed strong band characteristic of peptides. MALDI-TOF spectrum of the sample showed well-resolved group of peaks at m/z values 1,030.6, 1,046.7, 1,044.6, 1,060.5, 1,058.6, 1,058.7, and 1,074.6. The results indicated production of different isoforms of surfactin, ranging from C13-C15. Further, the sfp gene responsible for the production of surfactin was amplified and sequenced. In conclusion, this study showed that the mosquito pupicidal metabolite(s), produced by B. subtilis subsp. subtilis is the cyclic lipopeptide, surfactin. The mode of action of surfactin on pupae of mosquitoes is discussed. This is the first report on the mosquito pupicidal activity of surfactin produced by B. subtilis subsp. subtilis.