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The spatial pattern of infectious disease help us to understand

By Carlos Cooper,2014-04-29 23:52
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The spatial pattern of infectious disease help us to understand

    KALA-AZAR EPIDEMICS STUDY THROUGH SPATIAL ANALYSIS IN

    VAISHALI DISTRICT, BIHAR, INDIA.

G S Bhunia, S Kesari*, V Kumar & P Das.

* Corresponding author

Dr. Shreekant Kesari

    Scientist ‘B’

    Vector Biology & Control Division

    Rajendra Memorial Research Institute of Medical Sciences

    Indian Council of Medical Research

    Aagamkuan, Patna 800 007

    Bihar, India

    Phone + 091 612- 2631565, 2636651, 2631561

    Fax- +91 0612-2634379

    E-mail drskesari@sify.com

ABSTRACT

    The spatial pattern of infectious disease help us to understand their causes and controls insight. Especially in Kala-azar cases, forming a control programme and putting strategic action plans into practice became an important matter for health industry. GIS used to analyze the distribution pattern and geographic location of the disease as well as its relationship between vector, hosts and reservoir. In epidemiology GIS aids in visualizing and analyzing geographic distribution of disease with respect to time and space that is more difficult and impossible to perform in other way. The distribution of Kala-azar cases was presented on Kala-azar density maps which were calculated for each PHC based region. Data analysis has also shown that above 5 per cent of the total kala-azar cases reported in Bihar from the district from 1991-2005. Therefore it is a need to strengthen surveillance and control Kala-azar cases in these areas and pay special attention to these pockets.

    Keywords: Geographic Information System, Kala-azar, Temporal & Spatial analysis.

INTRODUCTION

    Kala-azar or Visceral Leishmaniasis in Vaishali district, Bihar, India is a major public health problems during last twenty years decay. Ecological factors, social infrastructure and other substantial characteristics of the area play a great role in distribution of the disease. Most of the cases incidence of disease can be identified by locations of affected people, vector of the disease and its pattern of spread. More than 90% of all the cases in India are reported from Bihar alone (Thakur CP, 2000). The increasing case fatality rate observed during the past 10years in amatter of serious concern among health care providers and policy makers (Zijlstra EE et al., 2003). GIS plays a vital role in strengthening the whole process of epidemiological surveillance information management and analysis. GIS is particularly useful to health professionals and administrators and day to day management (Colledge et al., 1996).

    Spatial epidemiology, also called health geography, considers the spatial and temporal characteristics of epidemiology. Epidemiologist finds out the spatial pattern of infectious disease which provides insight as to their causes and controls (Boscue FP et al,. 1999, Dobson AP, 2000). GIS and cartographic technique have created new opportunities for public health administrators to enhance planning, analysis, monitoring and management of kala-azar elimination.

    The application of GIS in Kala-azar elimination programme can be as simple as means of visualizing and analyzing geographic distribution and pattern of the disease through time. It relevant the spatio-temporal trends and pattern of the disease which is not possible in tabular or other formats. The Kala-azar cases and related information were displayed on the maps by GIS techniques to make Kala-azar cases data in spatial meaning.

GOALS OF THE STUDY

The main goal of the study is

    A. To be determined the kala-azar density areas and to be guiding component for

    geographical analysis research to factors causing Kala-azar on these area.

    B. Highlight the role of GIS in monitoring and management of Kala-azar control

    programme.

MATERIALS AND METHOD

Study Area

Vaishali district in Bihar, India lies between the latitude 23º38?N to 25º26?N and

    longitude 88º05?E to 90º11?E. The total area of the district is 2036 sq.km. and the total population of the district was 2718421 based on 2001 census data. The density of population of the district was 1335 and sex ratio was 920 in 2001. The district comprises an extensive plain formed by alluvium brought by the Ganga, Gandak and other rivers

    which flow through it. The district enjoying a bracing and healthy climate with three well marked seasons- summer, winter and rainy. January is the coldest month (Temperature <5ºC) and April-May is the warmest (Temperature 44ºC), and in the rainy season lasts till the end of September to the middle of October (Annual average rainfall 1154 mm). The soil of the district of the district is highly calcareous and the alluvial type. Rice, maize, wheat and sugarcane are the main crops of the district.

Data Used

    Different sets of data are to be used in this study. District boundary maps as well as block boundary maps were used which were collected from Land survey Revenue office, Patna, Bihar. Disease incidence report from 1991 to 2005 is used for this study. The data was collected from Rajendra Memorial Research Institute of Medical sciences, Agamkuan, Patna-800007, Bihar, India and the census data of 2001 was used for this study. Physical altitude map was generated from the topographical sheet (Scale 1:50, 000) of Vaishali, collected from Survey of India, Patna, Bihar.

Methodology

    All the maps were geo-referenced to real world co-ordinate system with respect to known reference point, based on geographic lat long and WGS 84 datum. Spatial data were digitized using ERDAS Imagine software. All the coverages were editing to remove digitization errors such as overshoot, undershoot, dangles, and labels for each polygon. Database was generated based on disease incidence report and linked with the vector layer. Digital maps were generated using ERDAS Imagine software and suitable cartographic techniques.

    Base Map (District and Block Map)

     Scanned the base map

     Geo-referencing

     Vector Layer Generation

     Error Detection and Remove

     Database Generation

     Linked the database with vector layer

    Thematic Map Generation

Flow chart to map Kala-azar in Vaishali.

RESULTS AND DISCUSSION

    Application of GIS in epidemiology through visualizing and analyzing geographic distribution of diseases through time, thus revealing spatio-temporal trends and patterns that would be more difficult or obscure to discover in other way (Nipada Ruankaew, 2005). It performs a spatial statistical task such as overlaying of different layers of information to determine dependencies and relationship between outbreaks and environmental factors. Climate plays a major role in disease occurrence. Higher temperature and humidity is required for the Kala-azar vector breeding. The annual maximum and minimum temperature ranges from 25?C-26?C and 14?C-16?C

    respectively and humidity ranges from 70-80% in the study site and the annual average precipitation of the district is 1154mm. These types of weather characteristics are responsible for the vector breeding (Napier LE, 1926). The density of vector (P.argentipes) is increases in summer and rainy season and in the winter season the density is less.

    The geographical distribution of the disease and annual number of human affected by Kala-azar in vaishali from the year 1991 to 2005 shows in figure 1. The Kala-azar cases data have been arranged in a database in the Microsoft Office Excel program. Polygon and Point layers were generated in ERDAS Imagine Software. After wards the data were linked with the Administrative boundaries of Vaishali district, used as a base graphical data. Cases data were categorized into 6 divisions with equal intervals per year and thematic maps were generated based on density of cases in different years which show the high, medium, and less affected PHCs of the district with different time intervals. From these analyses it is shown that in 1991 highest numbers of cases were in Lalganj and Mahua PHC (1389 & 1270) and lowest number of cases was in Raghopur PHC (79). In 2005 the highest number of cases was found in Raghopur PHC (275) and lowest number of cases was Hajipur PHC (37).

     Fig 1 Maps of different period from 1991-2005 (A-1991, B-1995, C-2001, D-2005) serve as an animation

    of phenomenon.

    Geo-spatial analysis provides the information of land cover, soil, terrain, and demographic characteristics (Thakur CP, 2000) of this area i.e. highly influenced the vector of the disease. Calcaric fluvisols and calcic cambisols type of soil are found in the district which has water holding capacity 200mm. This nature of soil enhances its capability of successful growth and abundance of edible shrubs, plants or agricultural crop. This characteristic of soil is considered favourable for sandflygenic condition (S. Sudhakar et al., 2006). Most of the area in the district is considered as arable land. The physical altitude of the area is less than 150m. Overlaying with other geo-referenced information, such as physical altitude, suggests a relationship between areas with a high frequency of Kala-azar cases and low altitude of this region (Figure 2).

     Fig 2 Physical altitude of the study area and its geographical distribution of human affected by Kala-Azar

    from 1991-2005.

    Kala-azar cases reported 1991-2005

    N Total Cumulative Annual Name of the

    (%) (%) rate Block

    Hajipur 1396 4.82 4.82 0.2

    Bidupur 1564 5.39 10.21 2.56

    Vaishali 1841 6.35 16.56 2.26

    Goraul 2236 7.71 24.27 3.76

    Mahannar 3487 12.02 36.29 3.54

    Mahua 4610 15.88 52.17 4.12

    Lalganj 3465 11.94 64.11 2.99

    Sahdai Buzurg 2278 7.85 71.96 3.56

    Jandaha 4383 15.11 87.07 2.93

    Patepur 3062 10.55 97.62 1.33

    Raghopur 690 2.38 100 1.44

    *Mean number of kala-azar cases reported per 10,000 per year, based on estimated district population and cases in 2001.

    Table 1 The cumulative reported incidence of kala-azar by PHCs (block) from 1991-2005.

    The Kala-azar cases seemed to be decreasing during the decade which is representing in figure 3. Analyzing the disease incidence data, it is observed that the high peaks were recorded in the year of 1991 and it is gradually decreases up to 2004 and again the peak is

    found in 2005. Annual kala-azar case totals ranged from 625 in 2002 to 9,658 in 1991, with a trend of rising incidence. Every year from 1991 to 2005, Vaishali district accounted for more than 5 per cent of the total kala-azar cases reported in Bihar, and disease transmission in the district appears to be the major focus fueling a sustained epidemic. Annual kala-azar incidence rates calculated using total district population in 2001 as the denominator (Table I) are misleading, since all PHCs in an affected district report cases (Figure 1). Using the population of the respective PHCs as the denominator, the annual incidence of kala-azar in Mahua PHCs is high (4.12) per 10,000, and the next most affected PHCs is Goraul (3.76) and the less affected PHCs is Hajipur (0.2) which is representing in table 1.

     Fig 3 Bar graph - showing the human affected by Kala-azar in different years in Vaishali district.

CONCLUSION

    The ability of GIS comprehensive Kala-azar control, however, comes from the flexibility and extensibility of the digital environment. Spatio-temporal analysis and mapping of Kala-azar for the years 1991-2005 depicted spatial spread of disease in Vaishali district. GIS provides epidemiologists and health practitioners with capabilities that are ideally suited for use in deadly disease monitoring, analysis, management the epidemiological surveillance and control of the disease. It also provides a framework for extending the GIS functionability over time. Therefore there is a need to strengthen surveillance in these areas and pay special attention to these pockets.

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