The environmental aspects of dengue and chikungunya outbreaks in India: GIS for epidemic control

Background: The dengue and chikungunya epidemics have major challenging problems and have become essentially a public health importance in India for the recent years, and it has been transmitted by the Aedes genus (Aedes aegypti or Ae. Albopictus) mosquito vectors. The huge chikungunya epidemic cases was reported in 213 districts especially in South India during 2006 and it happened in India, after 25 years period of breaks. The epidemic was showing good improvement of spatially declining trend, however, the dengue epidemics were reported from 24 states / union territories of India with 37070 cases and 227 deaths during 2012 and it steadily increased to become a very serious threat to the public. Materials and Methods: The ARC View 3.2 GIS was used for mapping the occurrences of epidemics situation in the country, geo-statistical analysis was carried out using SPSS 10.0, and ERDAS Imagine 8.5 image processing software was used for calibrating the NDVI value from IRS WiFS data. Results and discussion: The spatial analysis of geo-climate and the determinant variables with the epidemic cases provided results that temperature was experienced with a range of 22 to 31 oC, and relative humidity of 70 % to 90 %, and rain fall providing most suitable environment for fueling the huge number of profusion of Aedes mosquito species, with 95% significant and 5 % precision. Dengue and chikungunya epidemics in major metropolitan cities across the country, and rural areas in Maharashtra, Haryana, Uttar Pradesh, Pondicherry and Tamil Nadu have been associated with the huge number of containers of damaged house hold things in the coastal areas making it suitable for Aedes aegypti mosquitoes breeding. The regulation of irregular drinking water supply was supplied once in a week or 10 days, and hence, the village people have the practice of drinking water storage in big plastic container/ vessels and cement container, which was statistically significant with chi-square χ2 test, (P value <0.05). Chikungunya in Kerala was most associated with massive number of coconut shell used for collection of rubber milk in the rubber plantation in Kerala, and the massive pineapple cultivation in the state also fueling for dengue vector profusion in the state. The NDVI values of <0.4was due to the presence of actively photosynthesizing vegetation of rubber plantation, pineapple, forest cover, and hence, provided guidelines to stratification of areas under vulnerable to the dengue and chikungunya transmission. Conclusion: Climate, landscape and environment play an important role and has influence on the epidemic transmission across the country. The application of remote sensing and GIS was potentially useful for stratification of transmission risk areas, and perhaps, useful for epidemic control and management in the country.