Malaria is endemic throughout Ghana and continues to be a major cause of morbidity and mortality. In most parts of Ghana, malaria accounts for over 20% of childhood deaths. According to statistics by the National Malaria Control Programme, about 3.2 million malaria cases are recorded annually resulting in about 38,000 malaria deaths .
Epidemiological studies carried out in northern and southern Ghana have documented levels of malaria transmission, bed-net usage, trends in parasite density and severe anaemia, acquisition of parasitaemia in relation to age and sex, and also the prevalence of molecular markers of drug resistance in Plasmodium falciparum[2–4]. In the Kintampo districts of Ghana, malaria is a major health problem, which is ranked among the top three causes of mortality and morbidity . Until recently , no malaria epidemiological data had been reported from the Kintampo area, which is located in the middle part of Ghana.
The recent reports from Kintampo have shown decreasing parasite densities with increasing age [5, 6], amidst entomological inoculation rates (EIR) of 231–269 infective bites per person per year (ib/p/y) . In these reports, EIR, which estimates the level of exposure of an individual to malaria-infected mosquitoes, was used to estimate the malaria transmission rate. In other malaria endemic areas, molecular studies have shown that the number of clones of malaria parasites co-infecting a single host is a useful indicator of transmission intensity, as well as a guide in determining the immune status of the host [8, 9]. This view emanates from data, which have shown that an increase in transmission intensity generally correlates with a progressive increase in the average number of malaria parasite clones per host [8, 9]. High correlations between parasite density and multiplicity of infection (MOI) have also been reported in infants and young children but not in older individuals . Furthermore, the presence of a high number of clones or MOI is believed to be positively associated with protection against mild episodes of malaria in some circumstances. In holoendemic malarious areas high MOIs have not been related to clinical malaria among older children, [11–13] while in areas of lower transmission, positive relationships between high MOIs and clinical malaria have been observed [14–16].
A study of the multiplicity of malaria infections among an asymptomatic cohort of children and adults resident in the Kintampo districts, based on surveys carried out at two-monthly intervals, over a one-year period, is reported here. This study also examined the distribution of MOI and parasite densities in children less than five years, during different months of the study year as well as the relationships between monthly malaria transmission and merozoite surface protein 2 (MSP2) allelic variants.