Susceptibility of malaria vectors to insecticides in Gumla district, Jharkhand state, India.

Development of resistance to DDT in malaria vectors is being reported from various parts of India. Jharkhand state in India is one of the high malaria endemic states with Plasmodium falciparum accounting for 44% of the cases1. In order to find out the rationale of using DDT in vector control, this study was carried out on insecticide susceptibility of malaria vectors in 12 endemic villages of six PHCs, namely Gumla, Sisai, Raidih, Basia, Palkot and Bharno, in Gumla district of Jharkhand state. The Gumla district has uneven terrain with hills, valleys and forests at different altitudes and having a population of 0.7 million2 is highly malarious and situated close to the border of Simdega, a highly malarious district with a SPR of 14% in 20053. Slide positivity rate (SPR) in Gumla district in 2005 was 3.4% but had been substantially higher in the recent past, ranging from as low as 10% to as high as 19.7% between 1997 and 2003 in Jharkhand1. In Jharkhand state, indoor residual spray with DDT and insecticide-treated bed nets (ITBNs) are being used under vector control. There are 11 PHC’s in the district and all the areas have been receiving two rounds of DDT spray every year from 1958 onwards. In spite of control measures, malaria remains a major health problem in these areas. The main vectors of malaria in Gumla district are Anopheles culicifacies and An. fluviatilis (Diptera: Culicidae)4–5.