Mapping the geographical distribution of lymphatic filariasis in Zambia

Enala T Mwase; Anna-Sofie Stensgaard; Mutale Nsakashalo-Senkwe; Likezo Mubila; James Mwansa; Peter Songolo; Sheila T. Shawa; Paul Erik Simonsen

doi:10.1371/journal.pntd.0002714

Mapping the geographical distribution of lymphatic filariasis in Zambia

Enala T Mwase, Anna-Sofie Stensgaard, Mutale Nsakashalo-Senkwe, Likezo Mubila, James Mwansa, Peter Songolo, Sheila T. Shawa, Paul Erik Simonsen

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Abstract

BACKGROUND: Past case reports have indicated that lymphatic filariasis (LF) occurs in Zambia, but knowledge about its geographical distribution and prevalence pattern, and the underlying potential environmental drivers, has been limited. As a background for planning and implementation of control, a country-wide mapping survey was undertaken between 2003 and 2011. Here the mapping activities are outlined, the findings across the numerous survey sites are presented, and the ecological requirements of the LF distribution are explored.

METHODOLOGY/PRINCIPAL FINDINGS: Approximately 10,000 adult volunteers from 108 geo-referenced survey sites across Zambia were examined for circulating filarial antigens (CFA) with rapid format ICT cards, and a map indicating the distribution of CFA prevalences in Zambia was prepared. 78% of survey sites had CFA positive cases, with prevalences ranging between 1% and 54%. Most positive survey sites had low prevalence, but six foci with more than 15% prevalence were identified. The observed geographical variation in prevalence pattern was examined in more detail using a species distribution modeling approach to explore environmental requirements for parasite presence, and to predict potential suitable habitats over unsurveyed areas. Of note, areas associated with human modification of the landscape appeared to play an important role for the general presence of LF, whereas temperature (measured as averaged seasonal land surface temperature) seemed to be an important determinant of medium-high prevalence levels.

CONCLUSIONS/SIGNIFICANCE: LF was found to be surprisingly widespread in Zambia, although in most places with low prevalence. The produced maps and the identified environmental correlates of LF infection will provide useful guidance for planning and start-up of geographically targeted and cost-effective LF control in Zambia.

Original language	English
Article number	e2714
Journal	PLoS Neglected Tropical Diseases
Volume	8
Issue number	2
Number of pages	13
ISSN	1935-2735
DOIs	https://doi.org/10.1371/journal.pntd.0002714
Publication status	Published - Feb 2014

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Mapping the geographical distribution of lymphatic filariasis in ZambiaFinal published version, 2.53 MBLicence: CC BY

Cite this

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title = "Mapping the geographical distribution of lymphatic filariasis in Zambia",

abstract = "BACKGROUND: Past case reports have indicated that lymphatic filariasis (LF) occurs in Zambia, but knowledge about its geographical distribution and prevalence pattern, and the underlying potential environmental drivers, has been limited. As a background for planning and implementation of control, a country-wide mapping survey was undertaken between 2003 and 2011. Here the mapping activities are outlined, the findings across the numerous survey sites are presented, and the ecological requirements of the LF distribution are explored.METHODOLOGY/PRINCIPAL FINDINGS: Approximately 10,000 adult volunteers from 108 geo-referenced survey sites across Zambia were examined for circulating filarial antigens (CFA) with rapid format ICT cards, and a map indicating the distribution of CFA prevalences in Zambia was prepared. 78% of survey sites had CFA positive cases, with prevalences ranging between 1% and 54%. Most positive survey sites had low prevalence, but six foci with more than 15% prevalence were identified. The observed geographical variation in prevalence pattern was examined in more detail using a species distribution modeling approach to explore environmental requirements for parasite presence, and to predict potential suitable habitats over unsurveyed areas. Of note, areas associated with human modification of the landscape appeared to play an important role for the general presence of LF, whereas temperature (measured as averaged seasonal land surface temperature) seemed to be an important determinant of medium-high prevalence levels.CONCLUSIONS/SIGNIFICANCE: LF was found to be surprisingly widespread in Zambia, although in most places with low prevalence. The produced maps and the identified environmental correlates of LF infection will provide useful guidance for planning and start-up of geographically targeted and cost-effective LF control in Zambia.",

author = "Mwase, {Enala T} and Anna-Sofie Stensgaard and Mutale Nsakashalo-Senkwe and Likezo Mubila and James Mwansa and Peter Songolo and Shawa, {Sheila T.} and Simonsen, {Paul Erik}",

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AU - Mwase, Enala T

AU - Stensgaard, Anna-Sofie

AU - Nsakashalo-Senkwe, Mutale

AU - Mubila, Likezo

AU - Mwansa, James

AU - Songolo, Peter

AU - Shawa, Sheila T.

AU - Simonsen, Paul Erik

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N2 - BACKGROUND: Past case reports have indicated that lymphatic filariasis (LF) occurs in Zambia, but knowledge about its geographical distribution and prevalence pattern, and the underlying potential environmental drivers, has been limited. As a background for planning and implementation of control, a country-wide mapping survey was undertaken between 2003 and 2011. Here the mapping activities are outlined, the findings across the numerous survey sites are presented, and the ecological requirements of the LF distribution are explored.METHODOLOGY/PRINCIPAL FINDINGS: Approximately 10,000 adult volunteers from 108 geo-referenced survey sites across Zambia were examined for circulating filarial antigens (CFA) with rapid format ICT cards, and a map indicating the distribution of CFA prevalences in Zambia was prepared. 78% of survey sites had CFA positive cases, with prevalences ranging between 1% and 54%. Most positive survey sites had low prevalence, but six foci with more than 15% prevalence were identified. The observed geographical variation in prevalence pattern was examined in more detail using a species distribution modeling approach to explore environmental requirements for parasite presence, and to predict potential suitable habitats over unsurveyed areas. Of note, areas associated with human modification of the landscape appeared to play an important role for the general presence of LF, whereas temperature (measured as averaged seasonal land surface temperature) seemed to be an important determinant of medium-high prevalence levels.CONCLUSIONS/SIGNIFICANCE: LF was found to be surprisingly widespread in Zambia, although in most places with low prevalence. The produced maps and the identified environmental correlates of LF infection will provide useful guidance for planning and start-up of geographically targeted and cost-effective LF control in Zambia.

AB - BACKGROUND: Past case reports have indicated that lymphatic filariasis (LF) occurs in Zambia, but knowledge about its geographical distribution and prevalence pattern, and the underlying potential environmental drivers, has been limited. As a background for planning and implementation of control, a country-wide mapping survey was undertaken between 2003 and 2011. Here the mapping activities are outlined, the findings across the numerous survey sites are presented, and the ecological requirements of the LF distribution are explored.METHODOLOGY/PRINCIPAL FINDINGS: Approximately 10,000 adult volunteers from 108 geo-referenced survey sites across Zambia were examined for circulating filarial antigens (CFA) with rapid format ICT cards, and a map indicating the distribution of CFA prevalences in Zambia was prepared. 78% of survey sites had CFA positive cases, with prevalences ranging between 1% and 54%. Most positive survey sites had low prevalence, but six foci with more than 15% prevalence were identified. The observed geographical variation in prevalence pattern was examined in more detail using a species distribution modeling approach to explore environmental requirements for parasite presence, and to predict potential suitable habitats over unsurveyed areas. Of note, areas associated with human modification of the landscape appeared to play an important role for the general presence of LF, whereas temperature (measured as averaged seasonal land surface temperature) seemed to be an important determinant of medium-high prevalence levels.CONCLUSIONS/SIGNIFICANCE: LF was found to be surprisingly widespread in Zambia, although in most places with low prevalence. The produced maps and the identified environmental correlates of LF infection will provide useful guidance for planning and start-up of geographically targeted and cost-effective LF control in Zambia.

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JO - P L o S Neglected Tropical Diseases (Online)

JF - P L o S Neglected Tropical Diseases (Online)

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M1 - e2714

ER -

Mapping the geographical distribution of lymphatic filariasis in Zambia

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