Seasonal prevalence of Aedes aegypti in urban and industrial areas of Dibrugarh district, Assam.

In Dibrugarh district, one of the most populous districts of Assam, there is a potential risk of dengue virus transmission by the mosquito Aedes aegypti during the autumn, in the urban and industrial areas of the district. The seasonal patterns of oviposition activity and abundance of breeding sites of this vector were studied in two areas of the district. From January 2010 to December 2010, we examined a total of 767 ovitraps and 6562 water filled containers. Both study areas showed high percentages of positive ovitraps (urban: 18.2% and industrial: 45.08%) and positive breeding sites (urban: 22.8% and industrial: 53.5%) for Aedes aegypti with higher abundance in the post monsoon season. In industrial areas, percentages of breeding sites and positive ovitraps were high as compared to the percentages in the urban areas. The percentages of breeding sites and the positive ovitraps are high in autumn when compared to the percentages of the other seasons. In both the areas and with both the methodologies the highest infestation levels were registered in October (ovitraps: 29.3% and 65.1%, breeding sites: 27.5% and 65.2%). This highest abundance took place after heavy rainfall. A sharp decline in oviposition activity was observed when monthly room temperature decreased to16ºC with low rainfall (38 mm).