BHUBANESWAR: Anopheles Minimus mosquitoes, one of the major malaria vectors, have reappeared in the hyper-endemic districts of the State. It was believed to have disappeared for more than 45 years since the launching of the malaria eradication programme in Orissa. The re-emergence of the An. Minimus and the increasing concentration of An. Flutiviatilis, both incriminating vectors for the deadly falciparum malaria in the hyper-endemic districts of Keonjhar, Mayurbhanj and Sundargarh, have once again brought to focus intensification of prevention and control programmes in the regions, a study conducted by the Vector Control Research Centre (VCRC), Puducherry, under Indian Council of Medical Research (ICMR) has emphasised. An. Minimus was believed to have vanished with introduction of DDT residual spraying under the National Malaria Eradication Programme (NMEP). But it is still present and transmits malaria parasites raising questions over the coverage of spraying and vector control mechanisms in the hyper-endemic regions, said Dr SS Sahu, senior scientist and officer in-charge of the VCRC Field Station, Koraput.The study, which concentrated on Keonjhar district, more importantly has revealed that the indoor densities of both the species are higher in human dwellings than in other structures like cattle sheds and store houses. The density of both the vector species peaked during the rainy and the winter seasons. The vectors preferred to rest on the walls of dwellings, mostly at a very reachable height of three to four feet.During the present study, An. Minimus was collected from human dwellings and not from cattle sheds, indicating its preference to close human contact. In case of An. Flutiviatilis, the concentration was also more in human dwellings than in cattle sheds. The prevalence of both the species could be made accountable for the hyper-endemic situation of the area for falciparum malaria.Both the species are susceptible to DDT and synthetic pyrethroids. Indoor residual spraying with DDT/synthetic pyrethroids has been the main vector control measure in the district since 1958. “In such a situation, it is expected that malaria transmission is controlled but it has not been so as the disease continues to persist with high morbidity. This indicates improper implementation of indoor residual spraying over the years. Therefore, the residual spraying should be intensified across the region to reduce the vector density and ensure low malaria transmission,” stated Dr Sahu.The study on seasonal prevalence and resting behaviour of An. Minimus and An. Flutiviatilis in east-central India by Sahu, K Gunasekaran, P Vanamail and P Jambulingam has been published in the latest edition of Indian Journal of Medical Research.
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