Contributions of polyclonal malaria, gametocytemia, and pneumonia to infant severe anemia incidence in malaria hyperendemic Pemba, Tanzania.

The causative factors for severe anemia incidence in sub-Saharan Africa are multifactorial. In an observational, longitudinal study of two cohorts of about 300 infants followed-up for six months in a malaria hyperendemic area, the risk factors for severe anemia incidence were clinical malaria and pneumonia, which outweighed nutritional and sociodemographic factors. Severe anemia incidence was 1-2/year at age 2 months, peaked around 6-7/year at age 7-12 months, and decreased back to 1-2/year at age 16-22 months. The age-dependent increase of severe anemia incidence was shown to be parallel to the age-dependent increase of clinical malaria. Previous clinical malaria episodes increased the severe anemia risk by 80%, and gametocyte carriage and pneumonia at prior visit was associated with a six-fold increase and a > 10-fold increase, respectively. The role of pneumonia and malaria as risk factors, and areas for interventions for severe anemia, should not be underestimated.