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. 2019 Jul 8;17(1):124.
doi: 10.1186/s12916-019-1359-9.

Observational study: 27 years of severe malaria surveillance in Kilifi, Kenya

Patricia Njuguna  1 , Kathryn Maitland  1   2 , Amek Nyaguara  1 , Daniel Mwanga  1 , Polycarp Mogeni  1 , Neema Mturi  1 , Shebe Mohammed  1 , Gabriel Mwambingu  1 , Caroline Ngetsa  1 , Kenedy Awuondo  1 , Brett Lowe  1   3 , Ifedayo Adetifa  1   4 , J Anthony G Scott  1   4 , Thomas N Williams  1   2 , Sarah Atkinson  1   5 , Faith Osier  1 , Robert W Snow  1   3 , Kevin Marsh  1   3 , Benjamin Tsofa  1 , Norbert Peshu  1 , Mainga Hamaluba  1 , James A Berkley  1   3 , Charles R J Newton  1   6 , John Fondo  7 , Anisa Omar  7 , Philip Bejon  8
Affiliations

Observational study: 27 years of severe malaria surveillance in Kilifi, Kenya

Patricia Njuguna et al. BMC Med. .

Abstract

Background: Many parts of Africa have witnessed reductions in Plasmodium falciparum transmission over the last 15 years. Since immunity to malaria is acquired more rapidly at higher transmission, the slower acquisition of immunity at lower transmission may partially offset the benefits of reductions in transmission. We examined the clinical spectrum of disease and predictors of mortality after sustained changes in transmission intensity, using data collected from 1989 to 2016.

Methods: We conducted a temporal observational analysis of 18,000 children, aged 14 days to 14 years old, who were admitted to Kilifi County Hospital, Kenya, from 1989 to 2016 with malaria. We describe the trends over time of the clinical and laboratory criteria for severe malaria and associated risk of mortality.

Results: During the time periods 1989-2003, 2004-2008, and 2009-2016, Kilifi County Hospital admitted averages of 657, 310, and 174 cases of severe malaria per year including averages of 48, 14, and 12 malaria-associated deaths per year, respectively. The median ages in years of children admitted with cerebral malaria, severe anaemia, and malaria-associated mortality were 3.0 (95% confidence interval (CI) 2.2-3.9), 1.1 (95% CI 0.9-1.4), and 1.1 (95% CI 0.3-2.2) in the year 1989, rising to 4.9 (95% CI 3.9-5.9), 3.8 (95% CI 2.5-7.1), and 5 (95% CI 3.3-6.3) in the year 2016. The ratio of children with cerebral malaria to severe anaemia rose from 1:2 before 2004 to 3:2 after 2009. Hyperparasitaemia was a risk factor for death after 2009 but not in earlier time periods.

Conclusion: Despite the evidence of slower acquisition of immunity, continued reductions in the numbers of cases of severe malaria resulted in lower overall mortality. Our temporal data are limited to a single site, albeit potentially applicable to a secular trend present in many parts of Africa.

Keywords: Africa; Longitudinal surveillance; Mortality; Secular trend; Severe malaria.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Trends in mortality and clinical features of severe malaria over time. The trends over time are shown for clinical features of severe malaria among all children admitted with a parasite threshold of > 2500 μl. The percentage of children with a parasite threshold > 2500/μl where the relevant observation was positive is shown in red bars (left y-axis), and the absolute number of cases where the observation was positive is shown by the blue line (right y-axis). a All severe. b Cerebral. c Anaemia. d Resp. distress. e Other. f Mortality
Fig. 2
Fig. 2
Median ages for children admitted to Kilifi County Hospital. Median ages of presentation to hospital for specific phenotypes (see color legend) are shown over time with 95% confidence intervals calculated by the binomial exact method
See this image and copyright information in PMC

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