Plasmodium falciparum gametocyte carriage in asymptomatic children in western Kenya.
BACKGROUND
Studies on Plasmodium falciparum gametocyte development and dynamics have almost exclusively focused on patients treated with antimalarial drugs, while the majority of parasite carriers in endemic areas are asymptomatic. This study identified factors that influence gametocytaemia in asymptomatic children in the absence and presence of pyrimethamine-sulphadoxine (SP) antimalarial treatment.


METHODS
A cohort of 526 children (6 months-16 years) from western Kenya was screened for asexual parasites and gametocytes and followed weekly up to four weeks. Children with an estimated parasitaemia of > or =1,000 parasites/microl were treated with SP according to national guidelines. Factors associated with gametocyte development and persistence were determined in untreated and SP-treated children with P. falciparum mono-infection.


RESULTS
Gametocyte prevalence at enrollment was 33.8% in children below five years of age and decreased with age. In the absence of treatment 18.6% of the children developed gametocytaemia during follow-up; in SP-treated children this proportion was 29.8%. Age, high asexual parasite density and gametocyte presence at enrollment were predictive factors for gametocytaemia. The estimated mean duration of gametocytaemia for children below five, children from five to nine and children ten years and above was 9.4, 7.8 and 4.1 days, respectively.


CONCLUSIONS
This study shows that a large proportion of asymptomatic untreated children develop gametocytaemia. Gametocytaemia was particularly common in children below five years who harbor gametocytes for a longer period of time. The age-dependent duration of gametocytaemia has not been previously shown and could increase the importance of this age group for the infectious reservoir.
Bousema
J Teun
JT
Department of Medical Microbiology, University Medical Centre, Nijmegen, The Netherlands. t.bousema@ncmls.kun.nl
Gouagna
Louis C
LC
Drakeley
Chris J
CJ
Meutstege
Annemiek M
AM
Okech
Bernard A
BA
Akim
Ikupa N J
IN
Beier
John C
JC
Githure
John I
JI
Sauerwein
Robert W
RW
D000293:Adolescent; D000367:Age Factors; D000818:Animals; D000962:Antimalarials / Q000627:therapeutic use; D002353:Carrier State / Q000188:drug therapy / Q000453:epidemiology* / Q000469:parasitology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004197:Disease Reservoirs; D004338:Drug Combinations; D006801:Humans; D007223:Infant; D007630:Kenya / Q000453:epidemiology; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000453:epidemiology* / Q000469:parasitology; D008403:Mass Screening; D018512:Parasitemia / Q000188:drug therapy / Q000453:epidemiology* / Q000469:parasitology; D010963:Plasmodium falciparum / Q000302:isolation & purification; D015995:Prevalence; D011739:Pyrimethamine / Q000627:therapeutic use; D012307:Risk Factors; D013413:Sulfadoxine / Q000627:therapeutic use
D000962:Antimalarials; D004338:Drug Combinations; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D011739:Pyrimethamine