title: Haemoglobin variants and Plasmodium falciparum malaria in children under five years of age living in a high and seasonal malaria transmission area of Burkina Faso.
abstract: BACKGROUND
  Genetic factors play a key role in determining resistance/susceptibility to infectious disease. Susceptibility of the human host to malaria infection has been reported to be influenced by genetic factors, which could be confounders if not taken into account in the assessment of the efficacy of interventions against malaria. This study aimed to assess the relationship between haemoglobin genotypes and malaria in children under five years in a site being characterized for future malaria vaccine trials.
  
  
  METHODS
  The study population consisted of 452 children living in four rural villages. Hb genotype was determined at enrolment. Clinical malaria incidence was evaluated over a one-year period using combined active and passive surveillance. Prevalence of infection was evaluated via bi-annual cross-sectional surveys. At each follow-up visit, children received a brief clinical examination and thick and thin blood films were prepared for malaria diagnosis. A clinical malaria was defined as Plasmodium falciparum parasitaemia >2,500 parasites/μl and axillary temperature ≥37.5°C or reported fever over the previous 24 hours.
  
  
  RESULTS
  Frequencies of Hb genotypes were 73.2% AA; 15.0% AC; 8.2% AS; 2.2% CC; 1.1% CS and 0.2% SS. Prevalence of infection at enrolment ranged from 61.9%-54.1% among AA, AC and AS children. After one year follow-up, clinical malaria incidence (95% CI) (episodes per person-year) was 1.9 (1.7-2.0) in AA, 1.6 (1.4-2.1) in AC, and 1.7 (1.4-2.0) in AS children. AC genotype was associated with lower incidence of clinical malaria relative to AA genotype among children aged 1-2 years [rate ratio (95% CI) 0.66 (0.42-1.05)] and 2-3 years [rate ratio (95% CI) 0.37 (0.18-0.75)]; an association of opposite direction was however apparent among children aged 3-4 years. AS genotype was associated with lower incidence of clinical malaria relative to AA genotype among children aged 2-3 years [rate ratio (95% CI) 0.63 (0.40-1.01)].
  
  
  CONCLUSIONS
  In this cohort of children, AC or AS genotype was associated with lower risk of clinical malaria relative to AA genotype only among children aged one to three years. It would be advisable for clinical studies of malaria in endemic regions to consider haemoglobin gene differences as a potentially important confounder, particularly among younger children.
authors.affiliation: Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso.
authors.forename: Edith C
authors.initials: EC
authors.lastname: Bougouma
authors.forename: Alfred B
authors.initials: AB
authors.lastname: Tiono
authors.forename: Alphonse
authors.initials: A
authors.lastname: Ouédraogo
authors.forename: Issiaka
authors.initials: I
authors.lastname: Soulama
authors.forename: Amidou
authors.initials: A
authors.lastname: Diarra
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Yaro
authors.forename: Espérance
authors.initials: E
authors.lastname: Ouédraogo
authors.forename: Souleymane
authors.initials: S
authors.lastname: Sanon
authors.forename: Amadou T
authors.initials: AT
authors.lastname: Konaté
authors.forename: Issa
authors.initials: I
authors.lastname: Nébié
authors.forename: Nora L
authors.initials: NL
authors.lastname: Watson
authors.forename: Megan
authors.initials: M
authors.lastname: Sanza
authors.forename: Tina J T
authors.initials: TJ
authors.lastname: Dube
authors.forename: Sodiomon B
authors.initials: SB
authors.lastname: Sirima
mesh_terms: D001831:Body Temperature; D002050:Burkina Faso / Q000453:epidemiology; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006454:Hemoglobins / Q000145:classification / Q000235:genetics*; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D016778:Malaria, Falciparum / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics*; D008297:Male; D018512:Parasitemia / Q000175:diagnosis / Q000453:epidemiology; D010963:Plasmodium falciparum / Q000302:isolation & purification; D015995:Prevalence
chemical_list: D006454:Hemoglobins