Plasmodium falciparum gametocyte dynamics in areas of different malaria endemicity.
BACKGROUND
The aim of this study was to identify and compare factors associated with Plasmodium falciparum gametocyte carriage in three regions of differing malaria endemicity.


METHODS
Retrospective data from Thailand, The Gambia and Tanzania were used. The data came from large prospective field-based clinical trials, which investigated gametocyte carriage after different anti-malarial drug treatments.


RESULTS
Gametocytaemia was detected during the observation period in 12% of patients (931 out of 7548) in Thailand, 34% (683 out of 2020) in The Gambia, and 31% (430 out of 1400) in Tanzania (p < 0.001). Approximately one third (33%, 680/2044) of the patients with gametocytaemia during the observation period, already had patent gametocytaemia at enrolment (day 0 or day 1): 35% (318/931) in Thailand, 37% (250/683) in The Gambia, 26% (112/430) in Tanzania. Maximum gametocytaemia was usually observed on or before the seventh day after starting treatment (93% in Thailand, 70% in Tanzania and 78% in The Gambia). Lowest gametocyte carriage rates were observed following treatment with artemisinin derivatives, while sulphadoxine-pyrimethamine (SP) was associated with significantly greater development of gametocytaemia than other drug treatments (p < 0.001). The duration of gametocyte carriage was shorter in Thailand by 86% and Tanzania by 65% than in The Gambia. Gametocyte carriage was 27% longer among people presenting with anaemia, and was shorter in duration among patients who received artemisinin derivatives, by 27% in Thailand and by 71% in Tanzania and The Gambia.


CONCLUSIONS
This study confirms the independent association of gametocytaemia with anaemia, and the significantly lower prevalence and duration of gametocyte carriage following treatment with an artemisinin derivative. The large differences in gametocyte carriage rates between regions with different levels of malaria transmission suggest that drug interventions to prevent transmission will have different effects in different places.
Stepniewska
Kasia
K
Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok 10400, Thailand. kasia@tropmedres.ac
Price
Ric N
RN
Sutherland
Colin J
CJ
Drakeley
Chris J
CJ
von Seidlein
Lorenz
L
Nosten
Francois
F
White
Nicholas J
NJ
D000293:Adolescent; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D037621:Artemisinins / Q000494:pharmacology / Q000627:therapeutic use*; D002353:Carrier State / Q000188:drug therapy / Q000453:epidemiology / Q000469:parasitology*; D002648:Child; D002675:Child, Preschool; D004338:Drug Combinations; D019353:Endemic Diseases; D005260:Female; D005714:Gambia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D053208:Kaplan-Meier Estimate; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000453:epidemiology; D008297:Male; D015999:Multivariate Analysis; D018512:Parasitemia / Q000188:drug therapy* / Q000453:epidemiology / Q000469:parasitology; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000254:growth & development; D016016:Proportional Hazards Models; D011739:Pyrimethamine / Q000494:pharmacology / Q000627:therapeutic use*; D012189:Retrospective Studies; D013413:Sulfadoxine / Q000494:pharmacology / Q000627:therapeutic use*; D013636:Tanzania / Q000453:epidemiology; D013785:Thailand / Q000453:epidemiology
D000962:Antimalarials; D037621:Artemisinins; D004338:Drug Combinations; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; C031327:artemisinin; D011739:Pyrimethamine