title: Identification of different malaria patterns due to Plasmodium falciparum and Plasmodium vivax in Ethiopian children: a prospective cohort study.
abstract: 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.
authors.affiliation: Institute of Health and Society (IRSS), Université catholique de Louvain, Brussels, Belgium.|Department of Statistics, Natural Science College, Jimma University, Jimma, Ethiopia.
authors.forename: Dinberu
authors.initials: D
authors.lastname: Seyoum
authors.affiliation: Department of Statistics and Operations Research, University of Limpopo, Polokwane, 0727, South Africa.
authors.forename: Yehenew Getachew
authors.initials: YG
authors.lastname: Kifle
authors.affiliation: INSERM EMI 0338 (Biostatistics), Université Victor Segalen Bordeaux 2, 146 rue Leo Saignat, 33076, Bordeaux Cedex, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Rondeau
authors.affiliation: Department of Laboratory Technology Science and Pathology, College of Public Health and Medical Science, Jimma University, Jimma, Ethiopia.
authors.forename: Delenasaw
authors.initials: D
authors.lastname: Yewhalaw
authors.affiliation: Department of Comparative Physiology and Biometrics, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium.
authors.forename: Luc
authors.initials: L
authors.lastname: Duchateau
authors.affiliation: Institute of Health and Society (IRSS), Université catholique de Louvain, Brussels, Belgium.|Institute of Tropical Medicine "Alexander von Humboldt", Universidad Peruana Cayetano Heredia, Lima, Peru.
authors.forename: Angel
authors.initials: A
authors.lastname: Rosas-Aguirre
authors.affiliation: Institute of Health and Society (IRSS), Université catholique de Louvain, Brussels, Belgium. niko.speybroeck@uclouvain.be.
authors.forename: Niko
authors.initials: N
authors.lastname: Speybroeck
mesh_terms: D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005002:Ethiopia / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000469:parasitology; D016780:Malaria, Vivax / Q000453:epidemiology* / Q000469:parasitology; D008297:Male; D008962:Models, Theoretical; D010963:Plasmodium falciparum / Q000502:physiology*; D010966:Plasmodium vivax / Q000502:physiology*; D011446:Prospective Studies; D012307:Risk Factors
keywords: Ethiopia; Frailty model; Plasmodium falciparum; Plasmodium vivax; Recurrent malaria