Incidence of visceral leishmaniasis in the Vaishali district of Bihar, India: spatial patterns and role of inland water bodies

• Main Authors: Gouri Sankar Bhunia, Shreekant Kesari, Nandini Chatterjee, Dilip Kumar Pal, Vijay Kumar, Alok Ranjan, Pradeep Das
• Format: Article
• Language: English
• Published: PAGEPress Publications 2011-05-01
• Series: Geospatial Health
• Subjects: visceral leishmaniasis, inland water body, normalized differential pond index, India.
• Online Access: http://www.geospatialhealth.net/index.php/gh/article/view/173

The role of the distribution of inland water bodies with respect to the transmission of visceral leishmaniasis (VL) and its dominant vector, <em>Phlebotomous argentipes</em>, has been studied at the regional scale in Bihar, eastern India. The Landsat TM sensor multispectral scanning radiometer, with a spatial resolution of 30 m in the visible, reflective-infrared and shortwave- infrared (SWIR) bands, was used to identify water bodies using the normalized differential pond index (NDPI) calculated as follows: (Green – SWIR I)/(Green + SWIR I). Nearest neighbour and grid square statistics were used to delineate spatial patterns and distribution of the sandfly vector and the disease it transmits. The female <em>P. argentipes</em> sandfly was found to be associated with the distance from open water and particularly abundant near non-perennial river banks (68.4%; P &lt;0.001), while its association with rivers was focused further away from the water source (<em>X</em>2 = 26.3; P &lt;0.001). The results also reveal that the distribution of VL is clustered around non-perennial riverbanks, while the pattern is slightly random around the perennial river banks. The grid square technique illustrate that the spatial distribution of the disease has a much stronger correlation with lower density of open waters surfaces as well as with sandfly densities <em>(X2</em> = 26.0; P &lt;0.001). The results of our study suggest that inland water presence poses a risk for VL by offering suitable breeding sites for <em>P. argentipes</em>, a fact that should be taken into account when attempting to control disease transmission.