Variation in malariometric and red cell indices in children in the Mount Cameroon area following enhanced malaria control measures: evidence from a repeated cross-sectional study

Background: Following enhanced malaria control measures, such as nationwide free distribution of insecticide-treated bed nets (ITN) by the government of Cameroon, its impact on malariometric and red cell indices in children <= 14 years in Muea, in the Mount Cameroon area was evaluated. Methods: Two cross-sectional studies were conducted during the malaria transmission season (March-July) in 2006 (baseline) and 2013 (follow-up), respectively. The investigative methods included the use of a questionnaire to assess ITN use and coverage, clinical evaluation and laboratory investigations. Blood sample collected from each child was used for the preparation of blood films for detection of malaria parasites and density as well as full blood count determination using standard procedures and also an automated haematology analyzer. Results: The majority of children (81.5%) possessed an ITN in 2013. The proportion of effective users of ITN increased significantly from 20.9% (CI = 17.3-25%) in 2006 to 35.2% (CI = 31-39.7%) in 2013. The highest relative risk reduction in prevalence during the follow-up study was observed in malaria anaemia (79%, CI = 58.0-69.1% [69.1 to 14.5%]), followed by gametocytaemia (71.6%, CI = 58.9-80.3% [25.6 to 7.3%]), anaemia (64%, CI = 58.0-69.1% [80.1 to 28.9%]), and malaria parasitaemia (57.2%, CI = 51.4-62.3% [85.4 to 36.6%]). In the baseline survey, the prevalence of splenomegaly was significantly highest (chi(2) = 18.3, P <0.001) in the youngest group of children while in the follow-up study, it was highest in the oldest (chi(2) = 6.03, P = 0.049). The overall prevalence of mild, moderate and severe anaemia in the study population at baseline (59.6, 14.9, 6.3%) decreased significantly (P <0.001) to 24.4, 2.7 and 1.3%, respectively during the follow-up with the highest relative risk reduction in prevalence occurring in moderate anaemia (82.1%, CI = 67.3-90.2% [14.9 to 2.7%]). Microcytic anaemia also decreased significantly (P <0.001) from 56 to 7.7% during the follow-up survey. Conclusion: Following interventions, anaemia (moderate to severe) was a more sensitive measure to changes in malaria exposure and children between 11-14 years of age experienced a significant increase in malaria-related morbidity.