Seasonal prevalence & resting behaviour of Anopheles minimus Theobald & An. fluviatilis James (Diptera: Culicidae) in east-central India

BACKGROUND & OBJECTIVES: Anopheles minimus has recently been reported to have re-appeared in Keonjhar district of Orissa after a period of about 45 years of launching the malaria eradication programme. An. minimus and An. fluviatilis were the incriminated major malaria vectors in the district, endemic for falciparum malaria. The information on seasonal prevalence and resting behaviour of the vectors is crucial for implementing appropriate malaria control measures. Therefore, a study was undertaken on seasonal prevalence and resting behaviour of An. minimus and An. fluviatilis in this district. METHODS: Seven randomly selected villages of Keonjhar district, Orissa, were studied during August 2005 to November 2007. Daytime resting collections indoors and outdoors were made covering three seasons of the year. The Anopheles mosquitoes obtained from different habitats were identified. Collections were maintained separately according to different sites as well as heights of the walls in human dwellings. RESULTS: Among the indoor collections, the densities of An. minimus and An. fluviatilis were higher in human dwellings than cattle sheds. An. fluviatilis was the predominant (41.5%) species followed by An. minimus (26.3%) in human dwellings. The density of both the vector species in human dwellings peaked during rainy and winter seasons followed by summer. Walls were the most preferred site by these vectors for resting and the maximum number was collected at a height of 3 to 4 ft. INTERPRETATION & CONCLUSIONS: The resting behaviour of the vector species increases their contact with the sprayed walls and therefore, a quality residual spraying of human dwellings focusing indoor walls could interrupt the malaria transmission in this area.