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Identifying residual foci of Plasmodium falciparum infections for malaria elimination: the urban context of Khartoum, Sudan.

Nourein AB, Abass MA, Nugud AH, El Hassan I, Snow RW, Noor AM - PLoS ONE (2011)

Bottom Line: In 1999, overall prevalence was 2.5%, rising to 3.2% in 2000 and consistently staying below 1% in subsequent years.Spatial clustering of infections was present in each year but not statistically significant in the years 2001, 2002, 2004 and 2008.Spatial clusters of high infection were often located at the junction of the Blue and White Niles.

View Article: PubMed Central - PubMed

Affiliation: Department of Parasitology, Institute of Endemic Diseases, University of Khartoum, Khartoum, Sudan.

ABSTRACT

Background: Identifying the location and size of residual foci of infections is critical where malaria elimination is the primary goal. Here the spatial heterogeneity of Plasmodium falciparum infections within the urban extent of Khartoum state in Sudan is investigated using data from cross-sectional surveys undertaken from 1999 to 2008 to inform the Khartoum Malaria Free Initiative (KMFI).

Methods: From 1999-2008 the KMFI undertook cross-sectional surveys of 256 clusters across 203 random samples of residential blocks in the urban Khartoum state in September of each year. Within sampled blocks, at least five persons, including at least one child under the age of five years, were selected from each household. Blood smears were collected from the sampled individuals to examine the presence of P. falciparum parasites. Residential blocks were mapped. Data were analysed for spatial clustering using the Bernoulli model and the significance of clusters were tested using the Kulldorff scan statistic.

Results: A total of 128,510 malaria slide examinations were undertaken during the study period. In 1999, overall prevalence was 2.5%, rising to 3.2% in 2000 and consistently staying below 1% in subsequent years. From 2006, over 90% of all surveyed clusters reported no infections. Spatial clustering of infections was present in each year but not statistically significant in the years 2001, 2002, 2004 and 2008. Spatial clusters of high infection were often located at the junction of the Blue and White Niles.

Conclusion: Persisting foci of malaria infection in Khartoum are likely to distort wide area assessments and disproportionately affect future transmission within the city limits. Improved investments in surveillance that combines both passive and active case detection linked to a geographic information system and a more detailed analysis of the location and stability of foci should be undertaken to facilitate and track malaria elimination in the state of Khartoum.

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Map of Khartoum state showing the distribution of survey locations.A total of 256 P. falciparum prevalence surveys were undertaken in 203 locations (some survey locations were repeated in subsequent years) from 1999–2008. Inset is the state map of the Sudan showing the location of Khartoum state.
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pone-0016948-g001: Map of Khartoum state showing the distribution of survey locations.A total of 256 P. falciparum prevalence surveys were undertaken in 203 locations (some survey locations were repeated in subsequent years) from 1999–2008. Inset is the state map of the Sudan showing the location of Khartoum state.

Mentions: Khartoum state is one of the 26 states in Sudan with a total population of more than 5 million people in an area of approximately 28,000 Km2 [20], [21]. The Blue and White Nile rivers converge in Khartoum to form the River Nile along which the three administrative areas of the state: Khartoum, Khartoum Bahry and Omdurman are divided (Figure 1). The three areas differ in their malaria vulnerability due to differences in topographic, agricultural and the socioeconomic characteristics with small-scale irrigation concentrated in the Khartoum Bahry area [20]. The state experiences hot summers from April to July, patchy rains from August to October and dry winters from November to March. Anopheles arabiensis is the main vector of malaria [22] with the peak months of malaria transmission from September to November.


Identifying residual foci of Plasmodium falciparum infections for malaria elimination: the urban context of Khartoum, Sudan.

Nourein AB, Abass MA, Nugud AH, El Hassan I, Snow RW, Noor AM - PLoS ONE (2011)

Map of Khartoum state showing the distribution of survey locations.A total of 256 P. falciparum prevalence surveys were undertaken in 203 locations (some survey locations were repeated in subsequent years) from 1999–2008. Inset is the state map of the Sudan showing the location of Khartoum state.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3044149&req=5

pone-0016948-g001: Map of Khartoum state showing the distribution of survey locations.A total of 256 P. falciparum prevalence surveys were undertaken in 203 locations (some survey locations were repeated in subsequent years) from 1999–2008. Inset is the state map of the Sudan showing the location of Khartoum state.
Mentions: Khartoum state is one of the 26 states in Sudan with a total population of more than 5 million people in an area of approximately 28,000 Km2 [20], [21]. The Blue and White Nile rivers converge in Khartoum to form the River Nile along which the three administrative areas of the state: Khartoum, Khartoum Bahry and Omdurman are divided (Figure 1). The three areas differ in their malaria vulnerability due to differences in topographic, agricultural and the socioeconomic characteristics with small-scale irrigation concentrated in the Khartoum Bahry area [20]. The state experiences hot summers from April to July, patchy rains from August to October and dry winters from November to March. Anopheles arabiensis is the main vector of malaria [22] with the peak months of malaria transmission from September to November.

Bottom Line: In 1999, overall prevalence was 2.5%, rising to 3.2% in 2000 and consistently staying below 1% in subsequent years.Spatial clustering of infections was present in each year but not statistically significant in the years 2001, 2002, 2004 and 2008.Spatial clusters of high infection were often located at the junction of the Blue and White Niles.

View Article: PubMed Central - PubMed

Affiliation: Department of Parasitology, Institute of Endemic Diseases, University of Khartoum, Khartoum, Sudan.

ABSTRACT

Background: Identifying the location and size of residual foci of infections is critical where malaria elimination is the primary goal. Here the spatial heterogeneity of Plasmodium falciparum infections within the urban extent of Khartoum state in Sudan is investigated using data from cross-sectional surveys undertaken from 1999 to 2008 to inform the Khartoum Malaria Free Initiative (KMFI).

Methods: From 1999-2008 the KMFI undertook cross-sectional surveys of 256 clusters across 203 random samples of residential blocks in the urban Khartoum state in September of each year. Within sampled blocks, at least five persons, including at least one child under the age of five years, were selected from each household. Blood smears were collected from the sampled individuals to examine the presence of P. falciparum parasites. Residential blocks were mapped. Data were analysed for spatial clustering using the Bernoulli model and the significance of clusters were tested using the Kulldorff scan statistic.

Results: A total of 128,510 malaria slide examinations were undertaken during the study period. In 1999, overall prevalence was 2.5%, rising to 3.2% in 2000 and consistently staying below 1% in subsequent years. From 2006, over 90% of all surveyed clusters reported no infections. Spatial clustering of infections was present in each year but not statistically significant in the years 2001, 2002, 2004 and 2008. Spatial clusters of high infection were often located at the junction of the Blue and White Niles.

Conclusion: Persisting foci of malaria infection in Khartoum are likely to distort wide area assessments and disproportionately affect future transmission within the city limits. Improved investments in surveillance that combines both passive and active case detection linked to a geographic information system and a more detailed analysis of the location and stability of foci should be undertaken to facilitate and track malaria elimination in the state of Khartoum.

Show MeSH
Related in: MedlinePlus