Changes in malaria indices between 1999 and 2007 in The Gambia: a retrospective analysis

Abstract

Background: Malaria is a major cause of morbidity and mortality in Africa. International effort and funding for control has been stepped up, with substantial increases from 2003 in the delivery of malaria interventions to pregnant women and children younger than 5 years in The Gambia. We investigated the changes in malaria indices in this country, and the causes and public-health significance of these changes.

Methods: We undertook a retrospective analysis of original records to establish numbers and proportions of malaria inpatients, deaths, and blood-slide examinations at one hospital over 9 years (January, 1999-December, 2007), and at four health facilities in three different administrative regions over 7 years (January, 2001-December, 2007). We obtained additional data from single sites for haemoglobin concentrations in paediatric admissions and for age distribution of malaria admissions.

Findings: From 2003 to 2007, at four sites with complete slide examination records, the proportions of malaria-positive slides decreased by 82% (3397/10861 in 2003 to 337/6142 in 2007), 85% (137/1259 to 6/368), 73% (3664/16932 to 666/11333), and 50% (1206/3304 to 336/1853). At three sites with complete admission records, the proportions of malaria admissions fell by 74% (435/2530 to 69/1531), 69% (797/2824 to 89/1032), and 27% (2204/4056 to 496/1251). Proportions of deaths attributed to malaria in two hospitals decreased by 100% (seven of 115 in 2003 to none of 117 in 2007) and 90% (22/122 in 2003 to one of 58 in 2007). Since 2004, mean haemoglobin concentrations for all-cause admissions increased by 12 g/L (85 g/L in 2000-04 to 97 g/L in 2005-07), and mean age of paediatric malaria admissions increased from 3.9 years (95% CI 3.7-4.0) to 5.6 years (5.0-6.2).

Interpretation: A large proportion of the malaria burden has been alleviated in The Gambia. Our results encourage consideration of a policy to eliminate malaria as a public-health problem, while emphasising the importance of accurate and continuous surveillance.

Figure 1

Location of the five sites studied for hospital admissions, inpatient deaths, and laboratory slide microscopy in The Gambia The facilities at Fajara and Brikama serve mostly urban and peri-urban communities in the most densely populated part of the country near the coast; Farafenni is a small town with a large hospital serving a predominantly rural population; and facilities at Sibanor and Keneba are in large villages serving surrounding rural communities.

Figure 2

Monthly numbers (left panel) and yearly proportions (right panel) of malaria hospital admissions (A), deaths (B), and positive slides in outpatients (C) at the MRC in Fajara from January, 1999, to December, 2007 Monthly and yearly rainfall in the Greater Banjul Area over the period is also shown (D). Error bars indicate 95% CIs.

Figure 3

Age distribution of malaria cases admitted to the MRC ward from April, 1999, to December, 2007 (A) Mean age of paediatric cases (≤ 15 years) of malaria in every year from 1999 to 2007. Bars represent mean and error bars 95% CI. (B) Proportion of paediatric cases (≤ 15 years) of malaria in every age class in 1999–2000 and 2005–07.

Figure 4

Monthly numbers (left panel) and yearly proportions (right panel) of malaria hospital admissions in Sibanor (A) and Farafenni (B); malaria mortality in Sibanor (C); and malaria-positive slides in Brikama (D) and Keneba (E) from January, 2001, to December, 2007, and in Farafenni (F) from January, 2003, to December, 2007 Error bars indicate 95% CIs.

Figure 5

Proportion of maternally derived antibodies and frequency of new responses to malaria antigens in children born in 2003–04 The plot shows the percentage seropositive for IgG to the merozoite antigens AMA1 and MSP1-19 in 53 children at birth and at 4, 9, 18, and 36 months of age. The cut-off values for positivity were the mean plus 3 SD of ELISA OD (optical density) levels for 20 sera obtained from non-exposed individuals.

Figure 6

Rate of anaemia in children younger than 5 years who were admitted to Sibanor health facilities Data are from 7408 children from 2000 to 2007. (A) Monthly mean haemoglobin concentrations of patients. The months of the yearly malaria seasons (August–December) are marked with blue shading. (B) Percentage of children receiving blood transfusion every year from 2000 to 2007.