Altitude-dependent and -independent variations in Plasmodium falciparum prevalence in northeastern Tanzania

TY - JOUR

T1 - Altitude-dependent and -independent variations in Plasmodium falciparum prevalence in northeastern Tanzania

AU - Drakeley, Chris J

AU - Carneiro, Ilona

AU - Reyburn, Hugh

AU - Malima, Robert

AU - Lusingu, John P A

AU - Cox, Jonathan

AU - Theander, Thor G

AU - Nkya, Watoky M M M

AU - Lemnge, Martha M

AU - Riley, Eleanor M

N1 - Keywords: Adolescent; Adult; Altitude; Animals; Child; Child, Preschool; Cross-Sectional Studies; Female; Humans; Infant; Malaria, Falciparum; Male; Middle Aged; Rain; Tanzania

PY - 2005

Y1 - 2005

N2 - BACKGROUND: Effective malaria control requires information about intensity of transmission across large areas and populations. Estimates based on entomological factors lack precision and are not cost-effective to obtain. We tested altitude and rainfall measurements as correlates of transmission intensity in different ecological settings. METHODS: We conducted 2 cross-sectional surveys of approximately 12,000 people (1-45 years old) in 6 altitude transects (150-1800 m) in the Kilimanjaro and Tanga regions of Tanzania. Data were analyzed for associations with altitude and rainfall estimates by use of appropriate regression models. RESULTS: Plasmodium falciparum prevalence showed a negative relationship with altitude (19% and 21% decrease/100-m altitude increase, respectively, in children in Kilimanjaro and Tanga) and rainfall during the 3 months before the survey (46% decrease/100-mm rainfall increase in children in Kilimanjaro). Mean hemoglobin concentrations increased with altitude (0.05 and 0.09 g/dL/100-m altitude increase, respectively, in children in Kilimanjaro and Tanga) and rainfall (0.17 g/dL/100-mm rainfall increase in children and adults in Kilimanjaro). DISCUSSION: Altitude and rainfall were correlated with parasite prevalence and mean hemoglobin concentration; however, the relationship varied according to ecological setting. Climatological variables alone cannot predict malarial outcomes. Local variations in seasonality of malaria transmission--together with vector species composition, topography, host and parasite genetics, and socioeconomic factors--may influence malaria prevalence.

AB - BACKGROUND: Effective malaria control requires information about intensity of transmission across large areas and populations. Estimates based on entomological factors lack precision and are not cost-effective to obtain. We tested altitude and rainfall measurements as correlates of transmission intensity in different ecological settings. METHODS: We conducted 2 cross-sectional surveys of approximately 12,000 people (1-45 years old) in 6 altitude transects (150-1800 m) in the Kilimanjaro and Tanga regions of Tanzania. Data were analyzed for associations with altitude and rainfall estimates by use of appropriate regression models. RESULTS: Plasmodium falciparum prevalence showed a negative relationship with altitude (19% and 21% decrease/100-m altitude increase, respectively, in children in Kilimanjaro and Tanga) and rainfall during the 3 months before the survey (46% decrease/100-mm rainfall increase in children in Kilimanjaro). Mean hemoglobin concentrations increased with altitude (0.05 and 0.09 g/dL/100-m altitude increase, respectively, in children in Kilimanjaro and Tanga) and rainfall (0.17 g/dL/100-mm rainfall increase in children and adults in Kilimanjaro). DISCUSSION: Altitude and rainfall were correlated with parasite prevalence and mean hemoglobin concentration; however, the relationship varied according to ecological setting. Climatological variables alone cannot predict malarial outcomes. Local variations in seasonality of malaria transmission--together with vector species composition, topography, host and parasite genetics, and socioeconomic factors--may influence malaria prevalence.

U2 - 10.1086/429669

DO - 10.1086/429669

M3 - Journal article

C2 - 15838785

SN - 0022-1899

VL - 191

SP - 1589

EP - 1598

JO - Journal of Infectious Diseases

JF - Journal of Infectious Diseases

IS - 10

ER -