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Application of geographical information system (GIS) technology in the control of Buruli ulcer in Ghana
© Kenu et al.; licensee BioMed Central Ltd. 2014
Received: 9 December 2013
Accepted: 10 July 2014
Published: 16 July 2014
Buruli ulcer (BU) disease is a chronic debilitating skin disease caused by Mycobacteriumulcerans. It is associated with areas where the water is slow-flowing or stagnant. Policy makers take the necessary strategic and policy decisions especially where to target interventions based on available evidence including spatial distribution of the disease. Unfortunately, there is limited information on the spatial distribution of BU in Ghana. The aim of the study was to use Geographical Information System (GIS) technology to show the spatial distribution and hot spots of BU in Greater Accra and Eastern Regions in Ghana. The information could then be used by decision makers to make the necessary strategic and policy decisions, especially where to target intervention.
We conducted a community case search and spatial mapping in two districts in Eastern region (Akuapem South and Suhum- Kraboa-Coaltar) and two districts in Greater Accra region (Ga West and Ga South Municipalities) of Ghana to identify the spatial distribution of BU cases in the communities along the Densu River. These municipalities are already known to the Ministry of Health as having high case load of BU. Structured questionnaires on demographic characteristics, environmental factors and general practices were administered to the cases.
Using the E-trex Garmin Geographical Positioning System (GPS), the location of the case patient was marked along with any important attributes of the community. ArcGIS was used to generate maps showing BU distribution and hot spots.
Two hundred and fifty-seven (257) probable BU patients were enrolled in the study after the case search. These cases and their houses (or homes) were located with the GPS. The GIS maps generated showed a varying distribution of BU in the various communities. We observed clustering of BU patients downstream of the Densu River which had hitherto not been observed.
There is clustering of BU in areas where the river was most contaminated. The identified hot spots for BU should be targeted for interventions by policy makers to ensure effective control of BU in Ghana.
KeywordsBuruli ulcer Ghana GIS Mapping Clustering Case search
Buruli ulcer (BU) disease is a chronic debilitating skin disease caused by Mycobacterium ulcerans[1, 2]. It is one of the neglected tropical diseases and second commonest disease caused by Mycobacterium in Ghana and third globally [3, 4]. Currently, BU has been reported in over 30 countries, in the subtropical regions of Asia, Latin America, the Western Pacific region and Eastern and Central Africa [1, 2, 5, 6]. Even though it has been reported in other continents, West Africa is the region most affected [1, 6]. Bayley reported the first case of BU in Ghana in 1971 [7, 8] and in 1999 there was national search for BU which found a prevalence rate of 87.7 per 100 000 population in Ga West District with the highest number of active cases . Over 426 communities have reported cases of BU in Ghana. These communities are in Ashanti, Brong Ahafo, Eastern, Greater Accra and the Western regions of the country. Children less than fifteen years are mostly affected, even though persons of any age can be affected [6, 10, 11].
Mycobacterium ulcerans can be detected in both endemic and non-endemic sites although quantitative data is lacking for African countries . It occurs in discrete foci suggesting a spatial correlate with infection. Due to the disparity between hospital and community data, a detailed small-scale study on the location of houses with BU with respect to specific features will lead to the identification of spatial correlates of infection.
Spatial epidemiology has proven to be useful for understanding the geographical distribution of many diseases [13–17]. Geographic Information Systems (GIS) technology offers the unique opportunity and the ability to collect vast amount of data over large spatial region and to make spatial analysis for identification of hotspots. Policy makers take the necessary strategic and policy decisions especially where to target interventions based on available evidence including spatial distribution of the disease. Unfortunately, there is limited information on the spatial distribution of BU in Ghana. The aim of the study was to use GIS technology to show the spatial distribution and hot spots of BU in Greater Accra and Eastern Regions.
Profile of study area
Population of study districts
Akuapem South Municipality
Ga West Municipality
Ga South Municipality
Ga West and South were originally one municipality and separated after the 2000 population and housing census. These districts are considered urban settlements with 60% of their population living in urban communities. The Akans, who are the indigenes, form the majority in Akuapem South and Suhum-Kraboa-Coaltar districts while the Ga-Adangmes are the majority in Ga West and South Municipalities. However, people from all walks of life are increasingly migrating into these districts. A large proportion of the inhabitants of these districts especially those in the rural areas draw their water for domestic use from rivers, ponds, dugouts wells and other open water sources that are most often contaminated . The population of these districts is increasing and with it, the demand for safe and potable water. The increasing scarcity of potable water, forces more people to use unsafe water and thereby exposing themselves to water related disease such as BU.
The target population for the study was made up of all people living in the four districts at the time of study.
Any person aged 2 years or more who resided in the Suhum-Kraboa-Coaltar, Akuapem South, Ga west and South districts diagnosed of BU meeting the WHO clinical case definition for M. ulcerans disease. WHO clinical case definition for BU divides the disease into two stages: active and inactive. The active form is characterized by non-ulcerative (papules, nodules, plaques, and edema) and ulcerative disease. The distinctive features of a BU include undermining edges, white cotton wool-like appearance, and thickening and darkening of the skin surrounding the lesion.
Clinically diagnosed BU patients were recruited into the study following an active case search in the communities by trained Community Based Surveillance Volunteers, Community Health Workers and principal investigators in all the four districts from May 2010 to December 2011. The study area was divided into geographic study areas to make numbering of the communities, active case search, detailed data collection and case tracing more manageable. Communities within the study area and 10 kilometers radius from the Densu River were included in the study.
Use of trained Community Based Volunteers who had pictures of BU cases, skin conditions that could likely be BU and the case definition for BU
All children of School going age were thoroughly examined from head to toe for BU lesions
Self-referral through the use of the laminated pictures of BU lesions and WHO posters on BU posted in the various communities for awareness creation and easy identification of BU cases.
Samples were taken from all the active lesions for laboratory confirmation for positive polymerase chain reaction (PCR) or a positive Ziehl-Neelsen test for acid-fast bacilli in smears of lesions. The Laboratory confirmations were done at Noguchi Memorial Institute of Medical Research and all the positive cases were linked to care at any of the district/municipal hospitals closest to the patient eg Ga West Municipal Hospital, Kojo Ashong Health Centre, Pakro-Dago Health Centre and Nsawam Government Hospital.
E-trex Garmin Geographical positioning system (GPS) receiver was used to mark the location of each suspected BU patient. Houses, water bodies, field/crops, gardens, footpaths, rivers, roads and any other features of importance were also marked with the GPS receiver. In order to have accurate data from the Garmin eTrex Legend GPS receiver, the research assistants were trained on the use of the GPS receiver (DD, WGS-84, and WAAS-enabled). When the receiver had acquired signals from 4 or more satellites (3D fix), the coordinates were displayed on the screen and when the positional accuracy shown was less than or equal to 4meters (12.5 feet), then the point was taken. Accuracy Check Point (ACP) on the GPS receiver was set. Questionnaires administered collected information on demography (age, sex, place of residence, marital status, occupation, and educational status). GIS co-ordinates data taken for the cases were entered into an excel spread sheet and imported into ArcGIS software.
GIS maps were developed showing BU case distributions along the Densu River. Maps were generated based on BU cases per population of the communities and districts. Diameters called Buffer Zones were created around the places where BU cases reside to find out if there were particular environmental features there. Further analysis was done to determine the presence of clustering among the BU cases.
The Institutional Review Board (IRB) of Noguchi Memorial Institute for Medical Research and the Ethical Committee of Ghana Health Service gave ethical approval for the study. Permission was sought from community leaders, all adult subjects provided written informed consent and a parent or guardian of any child participant provided written informed consent on their behalf.
Results and discussion
A total of 257 suspected buruli ulcer cases were identified from over 400 communities over a period of 18 months. Of the 257 BU cases, 85.6% (220/257) were active and the rest inactive. Ninety percent (198/220) of the active cases were pre-ulcers and 22 presented as ulcers. One hundred and eighty-seven (187) of the suspected cases were in Akuapem South, 22 in Suhum Kraboa Coaltar Districts, 40 in Ga west and 8 in Ga South Municipalities. Though not the first active case search for Buruli ulcer in Ghana , the unique nature of the planning, involvement of all stakeholders and linking the patients identified into care makes this study unique in the country.
District prevalence of Buruli ulcer
The goal of the study was to determine the spatial distribution of the disease in the communities along the Densu river. The GPS maps generated clearly show where the cases were coming from, the clustering nature of the disease and the risk level per population of the districts. In addition, this study has clearly shown that BU cases were not present upstream of the Densu river but rather were only seen from the point where the river was contaminated and flowed slowly.
The authors would like to thank field workers for the community case search, Edith Tetteh, Dr Nana Konama Kotey, Dr Edwin Ampadu, Linda Seefeld and Dr Feena Veeltman for their enormous contribution.
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