Individual, household and environmental risk factors for malaria infection in Amhara, Oromia and SNNP regions of Ethiopia

We assessed malaria infection in relation to age, altitude, rainfall, socio-economic factors and coverage of control measures in a representative sample of 11 437 people in Amhara, Oromia and SNNP regions of Ethiopia in December 2006–January 2007. Surveys were conducted in 224 randomly selected clusters of 25 households (overall sample of 27 884 people in 5708 households). In 11 538 blood slides examined from alternate households (83% of those eligible), malaria prevalence in people of all ages was 4.1% (95% CI 3.4–4.9), with 56.5% of infections being Plasmodium falciparum. At least one mosquito net or one long-lasting insecticidal net (LLIN) was present in 37.0% (95% CI 31.1–43.3) and 19.6% (95% CI 15.5–24.5) of households, respectively. In multivariate analysis (n = 11 437; 82% of those eligible), significant protective factors were: number of LLINs per household (odds ratio [OR] per additional net = 0.60; 95% CI 0.40–0.89), living at higher altitude (OR per 100 m = 0.95; 95% CI 0.90–1.00) and household wealth (OR per unit increase in asset index = 0.79; 95% CI 0.66–0.94). Malaria prevalence was positively associated with peak monthly rainfall in the year before the survey (OR per additional 10 mm rain = 1.10; 95% CI 1.03–1.18). People living above 2000 m and people of all ages are still at significant risk of malaria infection