Identification of different malaria patterns due to Plasmodium falciparum and Plasmodium vivax in Ethiopian children: a prospective cohort study.
BACKGROUND
The identification of epidemiological pattern of infection with Plasmodium falciparum and Plasmodium vivax in malaria-endemic area, where multiple episodes are common, is important for intervention programmes.


METHODS
A longitudinal cohort study based on weekly house-to-house visits was conducted between July 2008 and June 2010 in 2040 children less than 10 years of age, living nearby the Gilgel-Gibe hydroelectric power dam reservoir in order to determine factors associated with increased P. vivax and P. falciparum incidence. Two types of multivariate frailty models were applied (using time-to-first malaria episode data and time-to-recurrent malaria episode data), allowing the estimation of adjusted hazard ratios (AHR) of potential risk factors (gender, age, proximity to the dam reservoir, and season) for species-specific malaria incidence.


RESULTS
Of 2040 children in 96 weeks of follow up, 864 children experienced at least one malaria episode: 685 due to P. falciparum in 548 children, and 385 due to P. vivax in 316 children. Plasmodium vivax and P. falciparum malaria incidence rates were 8.2 (95 % CI: 7.3-9.1) and 14.6 (95 % CI: 13.4-15.6) per 1000 children per month, respectively. According to the time-to-recurrent event models, children aged ≥7 years had a lower risk of presenting P. vivax episodes (AHR = 0.6; 95 % CI: 0.4-0.9), but a higher risk of P. falciparum episodes, when compared with children under ≤3 years (AHR = 1.2; 95 % CI: 1.1-1.6). In addition, P. vivax (AHR = 2.7; 95 % CI: 2.2-3.5) and P. falciparum (AHR = 16.9; 95 % CI: 14.3-20.2) episodes were respectively 2.7 and 16.9 times more frequent in the dry season than in the long rainy season.


CONCLUSIONS
The analysis of all malaria episodes (first and recurrent episodes) in the malaria cohort suggests different species-specific patterns of malaria disease in children, with mild seasonality in the incidence of P. vivax episodes mostly observed in younger age groups, and with marked seasonality in the incidence of P. falciparum episodes mainly seen in older children.
['Seyoum|Dinberu|D|', 'Kifle|Yehenew Getachew|YG|', 'Rondeau|Virginie|V|', 'Yewhalaw|Delenasaw|D|', 'Duchateau|Luc|L|', 'Rosas-Aguirre|Angel|A|', 'Speybroeck|Niko|N|']
D002648:Child D002675:Child, Preschool D015331:Cohort Studies D005002:Ethiopia D005260:Female D006801:Humans D015994:Incidence D007223:Infant D007231:Infant, Newborn D008137:Longitudinal Studies D016778:Malaria, Falciparum D016780:Malaria, Vivax D008297:Male D008962:Models, Theoretical D010963:Plasmodium falciparum D010966:Plasmodium vivax D011446:Prospective Studies D012307:Risk Factors
Plasmodium falciparum Plasmodium vivax Frailty model Ethiopia Recurrent malaria