Seasonal profiles of malaria infection, anaemia, and bednet use among age groups and communities in northern Ghana

We conducted all-age point prevalence surveys to profile the severity and seasonality of malaria and anaemia in Kassena-Nankana District of northern Ghana. Random cross-sectional surveys were timed to coincide with the end of low ( May 2001) and high ( November 2001) malaria transmission seasons and to yield information as to the potential value of haemoglobin (Hb) levels and parasitaemia as markers of malaria morbidity and/or malaria vaccine effect. Parasitaemia was found in 22% ( 515 of 2286) screened in May (dry-low transmission), and in 61% of the general population ( 1026 of 1676) screened in November (wet-high transmission). Malaria prevalence in May ranged from 4% ( infants < 6 months and adults 50 - 60 years) to 54% ( children 5 - 10 years). Age-specific malaria prevalence in November ranged from 38% ( adults 50 - 60 years) to 82% ( children 5 - 10 years). Differences between low- and high-transmission periods in the prevalence of severe anaemia ( SA) among young children ( 6 - 24 months) were unexpectedly comparable ( low, 3.9% vs. high, 5.4%; P = 0.52) and greatly reduced from levels measured in this same community and age group in November 2000 (12.5%) and November 1996 (22.0%). Despite the lower frequency of anaemia/SA in young children surveyed in 2001, it was still clear that this condition was strongly associated with parasitaemia and that children under 5 years of age experienced a significant drop in their mean Hb levels by the end of the high transmission season. Prevalence of parasitaemia was significantly lower ( P < 0.01) among infants and young children (< 2 years) whose parents reported the use of bednets. There was a significantly lower risk of parasitaemia among infants [ odds ratio (OR) 6 - 8] and young children (OR 3 - 4) living in the central, more urbanized sector of the study area.