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Geographical distribution of intestinal schistosomiasis and soil-transmitted helminthiasis and preventive chemotherapy strategies in Sierra Leone.

Koroma JB, Peterson J, Gbakima AA, Nylander FE, Sahr F, Soares Magalhães RJ, Zhang Y, Hodges MH - PLoS Negl Trop Dis (2010)

Bottom Line: Hookworm infection was negatively associated with population density and land surface temperature, and was high across Sierra Leone with a large cluster of high infection risk (prevalence >70%) in the north-eastern part of the country.Remarkably low prevalence of Ascaris lumbricoides (7.2%) and Trichuris trichiura (3.3%) was recorded when compared with results published in the 1990s.PCT for STH in the remaining district, Kono is justified annually.

View Article: PubMed Central - PubMed

Affiliation: National Onchocerciasis Control Program, Ministry for Health and Sanitation, Freetown, Sierra Leone.

ABSTRACT

Background: A national baseline mapping of schistosomiasis and soil-transmitted helminthiasis (STH) was performed in Sierra Leone. The aim was to provide necessary tools for the Ministry of Health and Sanitation to plan the intervention strategies in the national integrated control program on neglected tropical diseases according to the World Health Organization (WHO) guidelines for preventative chemotherapy (PCT) and for future monitoring and evaluation.

Methodology/principal findings: 53 primary schools were randomly selected through a two-staged random sampling throughout the country. Approximately one hundred children aged 5-16 years of age were systematically selected from each school and their stool samples examined in a field laboratory. A total of 5,651 samples were examined. Data were analyzed with multivariable logistic regression models using model-based geostatistics. Spatial analysis predicted that S. mansoni infection was positively associated with population density and elevation and that there was a large cluster of high risk of S. mansoni infection (prevalence >70%) in the north and most of the eastern areas of the country, in line with the observed prevalence in Kono (63.8-78.3%), Koinadugu (21.6-82.1%), Kailahun (43.5-52.6%), Kenema (6.1-68.9%) and Tonkolili (0-57.3%). Hookworm infection was negatively associated with population density and land surface temperature, and was high across Sierra Leone with a large cluster of high infection risk (prevalence >70%) in the north-eastern part of the country. Remarkably low prevalence of Ascaris lumbricoides (7.2%) and Trichuris trichiura (3.3%) was recorded when compared with results published in the 1990s.

Conclusions/significance: Results justify PCT for schistosomiasis for school age children and at-risk adults every year in high-risk communities in five districts and every two years in moderate-risk communities in one more district. The high prevalence of STH, particularly hookworm, coupled with widespread anemia according to a national report in Sierra Leone, suggests all but one district justifying biannual PCT for STH for pre-school children, school age children, and at-risk adults. PCT for STH in the remaining district, Kono is justified annually.

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Geographical distribution of intestinal schistosomiasis and soil-transmitted helminthiasis in Sierra Leone.Observed point prevalence is shown by locations of the selected schools: (A) intestinal schistosomiasis, (B) hookworm, (C) Ascaris lumbricoides, and (D) Trichuris trichiura.
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pntd-0000891-g001: Geographical distribution of intestinal schistosomiasis and soil-transmitted helminthiasis in Sierra Leone.Observed point prevalence is shown by locations of the selected schools: (A) intestinal schistosomiasis, (B) hookworm, (C) Ascaris lumbricoides, and (D) Trichuris trichiura.

Mentions: The coordinates of each sample site were recorded using hand-held units of global positioning system (GPS).The survey data were summarized as prevalence of infection by survey location. These summary data were plotted in a geographical information system (GIS) (ArcView version 9.3, ESRI, Redlands, CA) (Figure 1). Electronic data for land surface temperature (LST) and normalised difference vegetation index (NDVI) for a 5 km×5 km grid cell resolution were obtained from the National Oceanographic and Atmospheric Administration's (NOAA) Advanced Very High Radiometer (AVHRR; see Hay et al. [25] for details on these datasets) and the location of large perennial inland water bodies was obtained from the Food and Agriculture Organization of the United Nations (http://www.fao.org/geonetwork/srv/en/main.home) and the distance to the nearest perennial water body (DPWB) was extracted for each survey location in the GIS. A 5km resolution population surface derived from the Global Rural-Urban Mapping Project (GRUMP) beta product was obtained from the Center for International Earth Science Information Network (CIESIN) of the Earth Institute at Columbia University (http://sedac.ciesin.columbia.edu/gpw/global.jsp). Elevation data with a 5 km×5 km grid resolution, generated by a digital elevation model (DEM) from the Shuttle Radar Topography Mission (SRTM), were obtained from the Global Land Cover Facility (http://glcf.umiacs.umd.edu/index.shtml). All environmental datasets were linked to survey locations and values at each survey location were extracted in the GIS.


Geographical distribution of intestinal schistosomiasis and soil-transmitted helminthiasis and preventive chemotherapy strategies in Sierra Leone.

Koroma JB, Peterson J, Gbakima AA, Nylander FE, Sahr F, Soares Magalhães RJ, Zhang Y, Hodges MH - PLoS Negl Trop Dis (2010)

Geographical distribution of intestinal schistosomiasis and soil-transmitted helminthiasis in Sierra Leone.Observed point prevalence is shown by locations of the selected schools: (A) intestinal schistosomiasis, (B) hookworm, (C) Ascaris lumbricoides, and (D) Trichuris trichiura.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2990690&req=5

pntd-0000891-g001: Geographical distribution of intestinal schistosomiasis and soil-transmitted helminthiasis in Sierra Leone.Observed point prevalence is shown by locations of the selected schools: (A) intestinal schistosomiasis, (B) hookworm, (C) Ascaris lumbricoides, and (D) Trichuris trichiura.
Mentions: The coordinates of each sample site were recorded using hand-held units of global positioning system (GPS).The survey data were summarized as prevalence of infection by survey location. These summary data were plotted in a geographical information system (GIS) (ArcView version 9.3, ESRI, Redlands, CA) (Figure 1). Electronic data for land surface temperature (LST) and normalised difference vegetation index (NDVI) for a 5 km×5 km grid cell resolution were obtained from the National Oceanographic and Atmospheric Administration's (NOAA) Advanced Very High Radiometer (AVHRR; see Hay et al. [25] for details on these datasets) and the location of large perennial inland water bodies was obtained from the Food and Agriculture Organization of the United Nations (http://www.fao.org/geonetwork/srv/en/main.home) and the distance to the nearest perennial water body (DPWB) was extracted for each survey location in the GIS. A 5km resolution population surface derived from the Global Rural-Urban Mapping Project (GRUMP) beta product was obtained from the Center for International Earth Science Information Network (CIESIN) of the Earth Institute at Columbia University (http://sedac.ciesin.columbia.edu/gpw/global.jsp). Elevation data with a 5 km×5 km grid resolution, generated by a digital elevation model (DEM) from the Shuttle Radar Topography Mission (SRTM), were obtained from the Global Land Cover Facility (http://glcf.umiacs.umd.edu/index.shtml). All environmental datasets were linked to survey locations and values at each survey location were extracted in the GIS.

Bottom Line: Hookworm infection was negatively associated with population density and land surface temperature, and was high across Sierra Leone with a large cluster of high infection risk (prevalence >70%) in the north-eastern part of the country.Remarkably low prevalence of Ascaris lumbricoides (7.2%) and Trichuris trichiura (3.3%) was recorded when compared with results published in the 1990s.PCT for STH in the remaining district, Kono is justified annually.

View Article: PubMed Central - PubMed

Affiliation: National Onchocerciasis Control Program, Ministry for Health and Sanitation, Freetown, Sierra Leone.

ABSTRACT

Background: A national baseline mapping of schistosomiasis and soil-transmitted helminthiasis (STH) was performed in Sierra Leone. The aim was to provide necessary tools for the Ministry of Health and Sanitation to plan the intervention strategies in the national integrated control program on neglected tropical diseases according to the World Health Organization (WHO) guidelines for preventative chemotherapy (PCT) and for future monitoring and evaluation.

Methodology/principal findings: 53 primary schools were randomly selected through a two-staged random sampling throughout the country. Approximately one hundred children aged 5-16 years of age were systematically selected from each school and their stool samples examined in a field laboratory. A total of 5,651 samples were examined. Data were analyzed with multivariable logistic regression models using model-based geostatistics. Spatial analysis predicted that S. mansoni infection was positively associated with population density and elevation and that there was a large cluster of high risk of S. mansoni infection (prevalence >70%) in the north and most of the eastern areas of the country, in line with the observed prevalence in Kono (63.8-78.3%), Koinadugu (21.6-82.1%), Kailahun (43.5-52.6%), Kenema (6.1-68.9%) and Tonkolili (0-57.3%). Hookworm infection was negatively associated with population density and land surface temperature, and was high across Sierra Leone with a large cluster of high infection risk (prevalence >70%) in the north-eastern part of the country. Remarkably low prevalence of Ascaris lumbricoides (7.2%) and Trichuris trichiura (3.3%) was recorded when compared with results published in the 1990s.

Conclusions/significance: Results justify PCT for schistosomiasis for school age children and at-risk adults every year in high-risk communities in five districts and every two years in moderate-risk communities in one more district. The high prevalence of STH, particularly hookworm, coupled with widespread anemia according to a national report in Sierra Leone, suggests all but one district justifying biannual PCT for STH for pre-school children, school age children, and at-risk adults. PCT for STH in the remaining district, Kono is justified annually.

Show MeSH
Related in: MedlinePlus