Abstract
BackgroundInformation on the epidemiology of malaria is essential for designing and interpreting results of clinical trials of drugs, vaccines and other interventions. As a background to the establishment of a site for anti-malarial drugs and vaccine trials, the epidemiology of malaria in a rural site in central Ghana was investigated.MethodsActive surveillance of clinical malaria was carried out in a cohort of children below five years of age (n = 335) and the prevalence of malaria was estimated in a cohort of subjects of all ages (n = 1484) over a 12-month period. Participants were sampled from clusters drawn around sixteen index houses randomly selected from a total of about 22,000 houses within the study area. The child cohort was visited thrice weekly to screen for any illness and a blood slide was taken if a child had a history of fever or a temperature greater than or equal to 37.5 degree Celsius. The all-age cohort was screened for malaria once every eight weeks over a 12-month period. Estimation of Entomological Inoculation Rate (EIR) and characterization of Anopheline malaria vectors in the study area were also carried out.ResultsThe average parasite prevalence in the all age cohort was 58% (95% CI: 56.9, 59.4). In children below five years of age, the average prevalence was 64% (95% CI: 61.9, 66.0). Geometric mean parasite densities decreased significantly with increasing age. More than 50% of all children less than 10 years of age were anaemic. Children less than 5 years of age had as many as seven malaria attacks per child per year. The attack rates decreased significantly with increasing cut-offs of parasite density. The average Multiplicity of Infection (MOI) was of 6.1. All three pyrimethamine resistance mutant alleles of the Plasmodium falciparum dhfr gene were prevalent in this population and 25% of infections had a fourth mutant of pfdhps-A437G. The main vectors were Anopheles funestus and Anopheles gambiae and the EIR was 269 infective bites per person per year.ConclusionThe transmission of malaria in the forest-savanna region of central Ghana is high and perennial and this is an appropriate site for conducting clinical trials of anti-malarial drugs and vaccines.
Highlights
Information on the epidemiology of malaria is essential for designing and interpreting results of clinical trials of drugs, vaccines and other interventions
Prevalence of malaria The annual prevalence of malaria over the 12-month period in the all-age cohort was 58% and it ranged from 67.3% in May-June to 51.9% in November-December
The average annual prevalence in children below five years of age was 64% and it ranged from 74.3% in MayJune to 56.8% in NovemberDecember, a statistically significant difference between the two periods
Summary
Information on the epidemiology of malaria is essential for designing and interpreting results of clinical trials of drugs, vaccines and other interventions. Over 500 million episodes of malaria occur yearly, predominantly in sub-Saharan African children under five years of age, resulting in the death of approximately a million of these children [1,2,3]. Severe anaemia due to malaria occurs in 1.5 to 6.0 million African children per year with a case fatality rate of about 10%; respiratory distress, hypoglycaemia and overlapping conditions contribute a further 1-2 million cases with a mortality of nearly 20% [4]. Knowledge of the epidemiology of malaria is essential for the design and interpretation of the results of trials of drugs, vaccines and other anti-malarial interventions [710]. Prior to the conduct of a series of drug and vaccine trials, a study of the epidemiology of malaria were carried out in a forest area of central Ghana, an area where a few malaria studies have been done in recent years
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