Factors associated with high heterogeneity of malaria at fine spatial scale in the Western Kenyan highlands

Amrish Y. Baidjoe, Jennifer Claire Stevenson, Philip Knight, William Stone, Gillian Stresman, Victor Osoti, Euniah Makori, Chrispin Owaga, Wycliffe Odongo, Pauline China, Shehu Shagari, Simon Kariuki, Chris Drakeley, Jonathan Cox, Teun Bousema

Research output: Contribution to journalArticle

Abstract

Background: The East African highlands are fringe regions between stable and unstable malaria transmission. What factors contribute to the heterogeneity of malaria exposure on different spatial scales within larger foci has not been extensively studied. In a comprehensive, community-based cross-sectional survey an attempt was made to identify factors that drive the macro- and micro epidemiology of malaria in a fringe region using parasitological and serological outcomes. Methods: A large cross-sectional survey including 17,503 individuals was conducted across all age groups in a 100 km2 area in the Western Kenyan highlands of Rachuonyo South district. Households were geo-located and prevalence of malaria parasites and malaria-specific antibodies were determined by PCR and ELISA. Household and individual risk-factors were recorded. Geographical characteristics of the study area were digitally derived using high-resolution satellite images. Results: Malaria antibody prevalence strongly related to altitude (1350-1600 m, p <0.001). A strong negative association with increasing altitude and PCR parasite prevalence was found. Parasite carriage was detected at all altitudes and in all age groups; 93.2 % (2481/2663) of malaria infections were apparently asymptomatic. Malaria parasite prevalence was associated with age, bed net use, house construction features, altitude and topographical wetness index. Antibody prevalence was associated with all these factors and distance to the nearest water body. Conclusion: Altitude was a major driver of malaria transmission in this study area, even across narrow altitude bands. The large proportion of asymptomatic parasite carriers at all altitudes and the age-dependent acquisition of malaria antibodies indicate stable malaria transmission; the strong correlation between current parasite carriage and serological markers of malaria exposure indicate temporal stability of spatially heterogeneous transmission.

Original languageEnglish (US)
Article number15
JournalMalaria Journal
Volume15
Issue number1
DOIs
StatePublished - Jun 4 2016

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Malaria
Parasites
Antibodies
Age Groups
Cross-Sectional Studies
Polymerase Chain Reaction
Body Water
Epidemiology
Enzyme-Linked Immunosorbent Assay

Keywords

  • Elimination
  • Heterogeneity
  • Hotspots
  • Malaria
  • Plasmodium falciparum
  • Polymerase chain reaction
  • Risk-factors
  • Serology
  • Transmission

ASJC Scopus subject areas

  • Infectious Diseases
  • Parasitology

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Factors associated with high heterogeneity of malaria at fine spatial scale in the Western Kenyan highlands. / Baidjoe, Amrish Y.; Stevenson, Jennifer Claire; Knight, Philip; Stone, William; Stresman, Gillian; Osoti, Victor; Makori, Euniah; Owaga, Chrispin; Odongo, Wycliffe; China, Pauline; Shagari, Shehu; Kariuki, Simon; Drakeley, Chris; Cox, Jonathan; Bousema, Teun.

In: Malaria Journal, Vol. 15, No. 1, 15, 04.06.2016.

Research output: Contribution to journalArticle

Baidjoe, AY, Stevenson, JC, Knight, P, Stone, W, Stresman, G, Osoti, V, Makori, E, Owaga, C, Odongo, W, China, P, Shagari, S, Kariuki, S, Drakeley, C, Cox, J & Bousema, T 2016, 'Factors associated with high heterogeneity of malaria at fine spatial scale in the Western Kenyan highlands', Malaria Journal, vol. 15, no. 1, 15. https://doi.org/10.1186/s12936-016-1362-y
Baidjoe, Amrish Y. ; Stevenson, Jennifer Claire ; Knight, Philip ; Stone, William ; Stresman, Gillian ; Osoti, Victor ; Makori, Euniah ; Owaga, Chrispin ; Odongo, Wycliffe ; China, Pauline ; Shagari, Shehu ; Kariuki, Simon ; Drakeley, Chris ; Cox, Jonathan ; Bousema, Teun. / Factors associated with high heterogeneity of malaria at fine spatial scale in the Western Kenyan highlands. In: Malaria Journal. 2016 ; Vol. 15, No. 1.
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abstract = "Background: The East African highlands are fringe regions between stable and unstable malaria transmission. What factors contribute to the heterogeneity of malaria exposure on different spatial scales within larger foci has not been extensively studied. In a comprehensive, community-based cross-sectional survey an attempt was made to identify factors that drive the macro- and micro epidemiology of malaria in a fringe region using parasitological and serological outcomes. Methods: A large cross-sectional survey including 17,503 individuals was conducted across all age groups in a 100 km2 area in the Western Kenyan highlands of Rachuonyo South district. Households were geo-located and prevalence of malaria parasites and malaria-specific antibodies were determined by PCR and ELISA. Household and individual risk-factors were recorded. Geographical characteristics of the study area were digitally derived using high-resolution satellite images. Results: Malaria antibody prevalence strongly related to altitude (1350-1600 m, p <0.001). A strong negative association with increasing altitude and PCR parasite prevalence was found. Parasite carriage was detected at all altitudes and in all age groups; 93.2 {\%} (2481/2663) of malaria infections were apparently asymptomatic. Malaria parasite prevalence was associated with age, bed net use, house construction features, altitude and topographical wetness index. Antibody prevalence was associated with all these factors and distance to the nearest water body. Conclusion: Altitude was a major driver of malaria transmission in this study area, even across narrow altitude bands. The large proportion of asymptomatic parasite carriers at all altitudes and the age-dependent acquisition of malaria antibodies indicate stable malaria transmission; the strong correlation between current parasite carriage and serological markers of malaria exposure indicate temporal stability of spatially heterogeneous transmission.",
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AU - Baidjoe, Amrish Y.

AU - Stevenson, Jennifer Claire

AU - Knight, Philip

AU - Stone, William

AU - Stresman, Gillian

AU - Osoti, Victor

AU - Makori, Euniah

AU - Owaga, Chrispin

AU - Odongo, Wycliffe

AU - China, Pauline

AU - Shagari, Shehu

AU - Kariuki, Simon

AU - Drakeley, Chris

AU - Cox, Jonathan

AU - Bousema, Teun

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KW - Hotspots

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KW - Plasmodium falciparum

KW - Polymerase chain reaction

KW - Risk-factors

KW - Serology

KW - Transmission

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