title: A cohort study of Plasmodium falciparum infection dynamics in Western Kenya Highlands.
abstract: BACKGROUND
  The Kenyan highlands were malaria-free before the 1910s, but a series of malaria epidemics have occurred in the highlands of western Kenya since the 1980s. Longitudinal studies of the genetic structure, complexity, infection dynamics, and duration of naturally acquired Plasmodium falciparum infections are needed to facilitate a comprehensive understanding of malaria epidemiology in the complex Kenyan highland eco-epidemiological systems where malaria recently expanded, as well as the evaluation of control measures.
  
  
  METHODS
  We followed a cohort of 246 children residing in 3 villages at altitudes 1430 - 1580 m in western Kenya. Monthly parasitological surveys were undertaken for one year, yielding 866 P. falciparum isolates that were analyzed using 10 microsatellite markers.
  
  
  RESULTS
  Infection complexity and genetic diversity were high (HE = 0.787-0.816), with ≥83% of infections harboring more than one parasite clone. Diversity remained high even during the low malaria transmission season. There was no significant difference between levels of genetic diversity and population structure between high and low transmission seasons. Infection turn-over rate was high, with the average infection duration of single parasite genotypes being 1.11 months, and the longest genotype persistence was 3 months.
  
  
  CONCLUSIONS
  These data demonstrate that despite the relatively recent spread of malaria to the highlands, parasite populations seem to have stabilized with no evidence of bottlenecks between seasons, while the ability of residents to clear or control infections indicates presence of effective anti-plasmodial immune mechanisms.
authors.affiliation: Department of Medicine, Division of Infectious Diseases, University of California-San Francisco, CA 94143-0811, USA. fbaliraine@daad-alumni.de
authors.forename: Frederick N
authors.initials: FN
authors.lastname: Baliraine
authors.forename: Yaw A
authors.initials: YA
authors.lastname: Afrane
authors.forename: Dolphine A
authors.initials: DA
authors.lastname: Amenya
authors.forename: Mariangela
authors.initials: M
authors.lastname: Bonizzoni
authors.forename: Anne M
authors.initials: AM
authors.lastname: Vardo-Zalik
authors.forename: David M
authors.initials: DM
authors.lastname: Menge
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Githeko
authors.forename: Guiyun
authors.initials: G
authors.lastname: Yan
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D016054:DNA, Protozoan / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D015994:Incidence; D007630:Kenya / Q000453:epidemiology; D015810:Linkage Disequilibrium; D008137:Longitudinal Studies; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology*; D018895:Microsatellite Repeats; D010963:Plasmodium falciparum / Q000235:genetics* / Q000302:isolation & purification; D011156:Population Density; D012621:Seasons
chemical_list: D016054:DNA, Protozoan