Gouri Sankar Bhunia

Spatial and temporal variation and hotspot detection of kala-azar disease in Vaishali district (Bihar), India

BackgroundAn improved understanding in transmission variation of kala-azar is fundamental to conduct surveillance and implementing disease prevention strategies. This study investigated the spatio-temporal patterns and hotspot detection for reporting kala-azar cases in Vaishali district based on spatial statistical analysis.MethodsEpidemiological data from the study area during 2007–2011 was used to examine the dynamic space-time pattern of kala-azar outbreaks, and all cases were geocoded at a village level. Spatial smoothing was applied to reduce random noise in the data. Inverse distance weighting (IDW) is used to interpolate and predict the pattern of VL cases distribution across the district. Moran’s I Index (Moran’s I) statistics was used to evaluate autocorrelation in kala-azar spatial distribution and test how villages were clustered or dispersed in space. Getis-Ord Gi*(d) was used to identify the hotspot and cold spot areas within the study site.ResultsMapping kala-azar cases or incidences reflects the spatial heterogeneity in the incidence rate of kala-azar affected villages in Vaishali district. Kala-azar incidence rate map showed most of the highest endemic villages were located in southern, eastern and northwestern part of the district; in the middle part of the district generally show the medium occurrence of VL. There was a significant positive spatial autocorrelation of kala-azar incidences for five consecutive years, with Moran’s I statistic ranging from 0.04-0.17 (P <0.01). The results revealed spatially clustered patterns with significant differences by village. The hotspots showed the spatial trend of kala-azar diffusion (P < 0.01).ConclusionsThe results pointed to the usefulness of spatial statistical approach to improve our understanding the spatio-temporal dynamics and control of kala-azar. The study also showed the north-western and southern part of Vaishali district is most likely endemic cluster region. To employ exact and geographically suitable risk-reduction programmes, apply of such spatial analysis tools should suit a vital constituent in epidemiology research and risk evaluation of kala-azar.

Study of house-level risk factors associated in the transmission of Indian Kala-azar

BackgroundIn visceral leishmaniasis (VL), phlebotomine vectors are the main target to reduce for control measures. An attempt has been taken to delineate the association between Phlebotomous argentipes and housing characteristics between two districts e.g. endemic and non-endemic.MethodsA cross-sectional survey was conducted on 240 households for both the endemic (Vaishali district) and non-endemic (Lohardaga district) site. Logistic regression analysis was used to identify factors related to housing characteristics influencing suitable habitats for P. argentipes. Vector density estimated using a CDC light trap.ResultsThe proportion of P. argentipes in both endemic and non-endemic areas was significantly much higher (P < 0.001) when compared with the proportion of Sergentomiya and P. papatasi. The results of multilevel logistic regression analysis showed that mud plastered wall (P value = 0.001), mixed dwelling (P value = 0.002) and area (P value = 0.001) were strongly associated with the presence of vectors.ConclusionResult of the studied household characteristics provides an accurate, rapid assessment of house-level variation in risk. The results also have implications for maximizing surveillance efficacy of sandflies, which is likely to become increasingly important while formulating any control strategy.

Asymptomatic Leishmania infections in northern India: a threat for the elimination programme?

Visceral leishmaniasis (VL) continues to embody as a mammoth public health problem and hurdle to the socioeconomic development of Bihar, India. Interestingly, all leishmanial infections do not lead to overt clinical disease and may stay asymptomatic for a period of time. Asymptomatic cases of VL are considered as probable potential reservoirs of VL, and thus can play a major role in transmission of the disease in highly endemic areas of Bihar, India. They outnumber the exact disease burden in endemic areas of this region, thus jeopardizing the goal of the elimination program that is due by 2015. This article discusses the potential risk factors, epidemiological markers of transmission and requirement of highly sensitive diagnostic tools for efficient recognition of the high risk groups of conversion to symptomatic for proper designing of strategies for implementation of the control programs.

The Burden of Visceral Leishmaniasis in India: Challenges in Using Remote Sensing and GIS to Understand and Control

Visceral leishmaniasis (VL) continues to constitute immense public health problems and be an obstacle to socioeconomic development in India. The scrutiny of this disease remains a necessary step in its control, eradication, and prevention. Space technologies proffer new opportunities for rapid appraisal of endemic areas, stipulation of trustworthy estimation of populations at risk, prediction of disease distributions in areas that lack baseline data and are difficult to access, and guiding intervention strategies. Here, we focus on the epidemiology and control of VL in India and review remote sensing (RS) and GIS applications to date. For the original evidenced report, a search was done on electronic databases of PubMed, ERMSS, EQUEST and from online Internet searching to come across the recent research problems. We discuss the previous work conducted in this field, outlined potential new applications of GIS and RS techniques, and utilization of emerging satellite information, as they hold a promising area to further enhance VL risk mapping and prediction. Finally, we concluded with a discussion of strategies to overcome some of the perspective challenges of GIS and RS applications for VL control, so that supplementary and continued progress can be made to control this disease in India and elsewhere.

Morphometric Analysis of Kangshabati-Darkeswar Interfluves Area in West Bengal, India using ASTER DEM and GIS Techniques

The aim of the study is to delineate the morphometric characteristics of Kangshabati-Darkeswar Interfluves Area using remote sensing and GIS technology. 10 km2 grids were elaborate to delineate the relief characteristics using Advance Space Thermal Emission and Radiometer (ASTER) data. Drainage networks were automatically extracted from digital aster elevation models. Second order local polynomial (LP) interpolation technique was used to estimate the surface characteristics of the study area using ArcGIS 9.3. The absolute elevation of the study region is extended between 4.0-949.29 m with an average elevation of 484.50 m. The highest relative relief resulted 833.69 m, whereas the average ruggedness index of the study area is recorded as 0.09 per 10 km2 area. The average drainage density of the study area was computed 0.73/sq. km and the highest drainage intensity are recorded as 9.58/10 km2 grid area. The average length of overland flow of the study area was 2.56/10 km2 grid areas. The result of the study highlights an about the spatial distribution of relief and hydrological characteristics which may provide the knowledge to devise and accomplish an appropriate plan to progress agriculture and others allied activities. Hence, from the study, it can be concluded that remote sensing data (ASTER –DEM) coupled with GIS techniques prove to be a competent tool in morphometric analysis and the data can be used for basin or interfluves area management and other hydrological studies in future.

A comparative evaluation of end emic and non-endemic region of visceral leishmaniasis (Kala-azar) in India with ground survey and space technology

In visceral leishmaniasis, phlebotomine vectors are targets for control measures. Understanding the ecosystem of the vectors is a prerequisite for creating these control measures. This study endeavours to delineate the suitable locations of Phlebotomus argentipes with relation to environmental characteristics between endemic and non-endemic districts in India. A cross-sectional survey was conducted on 25 villages in each district. Environmental data were obtained through remote sensing images and vector density was measured using a CDC light trap. Simple linear regression analysis was used to measure the association between climatic parameters and vector density. Using factor analysis, the relationship between land cover classes and P. argentipes density among the villages in both districts was investigated. The results of the regression analysis indicated that indoor temperature and relative humidity are the best predictors for P. argentipes distribution. Factor analysis confirmed breeding preferences for P. argentipes by landscape element. Minimum Normalised Difference Vegetation Index, marshy land and orchard/settlement produced high loading in an endemic region, whereas water bodies and dense forest were preferred in non-endemic sites. Soil properties between the two districts were studied and indicated that soil pH and moisture content is higher in endemic sites compared to non-endemic sites. The present study should be utilised to make critical decisions for vector surveillance and controlling Kala-azar disease vectors.

Spatial variability of groundwater quality of Sabour block, Bhagalpur district (Bihar, India)

This paper examines the quality of groundwater of Sabour block, Bhagalpur district of Bihar state, which lies on the southern region of Indo-Gangetic plains in India. Fifty-nine samples from different sources of water in the block have been collected to determine its suitability for drinking and irrigational purposes. From the samples electrical conductivity (EC), pH and concentrations of Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Potassium (K+), carbonate ion (CO32−), Bicarbonate ion (HCO3-), Chloride ion (Cl−), and Fluoride (F−) were determined. Surface maps of all the groundwater quality parameters have been prepared using radial basis function (RBF) method. RBF model was used to interpolate data points in a group of multi-dimensional space. Root Mean Square Error (RMSE) is employed to scrutinize the best fit of the model to compare the obtained value. The mean value of pH, EC, Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, and F− are found to be 7.26, 0.69, 38.98, 34.20, 16.92, 1.19, 0.02, and 0.28, respectively. Distribution of calcium concentration is increasing to the eastern part and K+ concentrations raise to the downstream area in the southwestern part. Low pH concentrations (less than 6.71) occur in eastern part of the block. Spatial variations of hardness in Sabour block portraying maximum concentration in the western part and maximum SAR (more than 4.23) were recorded in the southern part. These results are not exceeding for drinking and irrigation uses recommended by World Health Organization. Therefore, the majority of groundwater samples are found to be safe for drinking and irrigation management practices.

Spatial analysis of soil properties using GIS based geostatistics models

Accurate assessment of the spatial variability of soil properties is key component of the agriculture ecosystem and environment modeling. The main objective of the present study is to measure the soil properties and their spatial variability. A combination of conventional analytical methods and geostatistical methods were used to analyze the data for spatial variability. In November 2014 a total of 32 soil samples were collected in the field through random sampling in Medinipur Sadar block of Paschim Medinipur district in West Bengal (India). Soil properties of pH, electric conductivity (EC), phosphorus (P), potassium (K), and organic carbon (OC) were estimated using the standard analytical methods. A classical ordinary kriging (OK) interpolation was used for direct visualization of soil properties. The spatial distribution of EC, pH, and OC in soil are influenced by structural factors, such as climate, parent material, topography, soil properties and other natural factors. The semivariograms of the six soil properties were fit with exponential curve and root mean square error value is near about zero (0). Finally, spatial distribution and correlation between OC and other soil properties is shown by overlay of maps in GIS environment. The present study suggest that the OK interpolation can directly reveal the spatial distribution of soil properties and the sample distance in this study is sufficient for interpolation.

Spatial distribution of P. argentipes in association with agricultural surrounding environment in North Bihar, India.

INTRODUCTION Phlebotomus argentipes is considered to be one of the major control measure targets in eradicating visceral leishmaniasis (VL). This study demonstrates the spatial association of P. argentipes abundance in relation to agricultural environment in the endemic area of north Bihar. METHODOLOGY Vector data were collected from the 95 villages of the study area using a handheld aspiration technique. Space technology and ground observationwere made to estimate the environmental characteristics. RESULTS A total of 1,663 P. argentipes were collected between April and November 2011. Results showed negative and significant association between P. argentipes density and proximity to the agricultural land in both the dry (r = -0.39) and wet seasons (r = -0.55), respectively. A strong and positive association was observed between relative humidity and P. argentipes abundance (r = 0.55). Results illustrated a very strong positive association between soil moisture and P. argentipes abundance (r = 0.58). The agricultural land class density and the spatial abundance of P. argentipes showed a very strong and positive association (r = 0.46). CONCLUSIONS This study will help in understanding the advantage of agricultural land use practices to delineate of P. argentipes habitat suitability, which may strengthen existing control strategies in this endemic area.

Vegetation Influence on Runoff and Sediment Yield in the Lateritic Region: An Experimental Study

The lateritic badland topography (Western part of West Bengal, India) is prone to severe erosion, caused by heavy rainfall events of short duration and high intensities. Five catchments were instrumented in order to study the rainfall– runoff process and soil management impact on runoff and/or sediment yield. In the five micro catchments (Rangamati, Medinipur), characterized by a homogeneity of surface geology, a data set of about 43 rainfall–runoff events covering the January 2012 to Sept, 2012 period was generated by field monitoring. Multiple regression analysis is done to define the role of rainfall volume vis-a-vis vegetation cover on sediment yield. The physical and chemical properties of soil were estimated at the initial and final stage of the gully development in the lower gully basin area. Temporal assessment of soil erosion indicated that increase of rainfall volume protracted the whole process of sediment production, and vegetation on the slope delayed that process. Results indicated that the highest spatial coverage of vegetation (73.5%) yield very low amount of soil [basin-I experimental site (Adjusted R2 = 0.56)] whereas, the lowest spatial coverage (5.9%) leads to severe soil loss [(basin-IV experimental site (Adjusted R2 = 0.33)]. Results illustrated that at the initial stage, the percent of sand was maximum in the upper catchment of each gully basin and the concentration of silt and clay is less. Gradually as vegetation starts trapping the sediment, composition of soil changes registering higher percentage of finer particles. Again, the nutrients detached from the upper catchment were arrested by check dams that induced nutrients supply and water storage, which in turn, increased the growth of vegetation. This result proved the significance of vegetation cover to curb soil erosion and it may help the planners and managers to take proper decision for the conservation of soil.