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A novel approach for measuring the burden of uncomplicated Plasmodium falciparum malaria: application to data from Zambia.

Crowell V, Yukich JO, Briët OJ, Ross A, Smith TA - PLoS ONE (2013)

Bottom Line: The use of burden estimates that do not consider effects of treatment, leads to under-estimation of the impact of improvements in case management.Official estimates of burden very likely massively underestimate the impact of the roll-out of ACT as first-line therapy across Africa.The estimates of recall bias, and of the numbers of days with illness contributing to single illness recalls, could be applied more generally.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.

ABSTRACT
Measurement of malaria burden is fraught with complexity, due to the natural history of the disease, delays in seeking treatment or failure of case management. Attempts to establish an appropriate case definition for a malaria episode has often resulted in ambiguities and challenges because of poor information about treatment seeking, patterns of infection, recurrence of fever and asymptomatic infection. While the primary reason for treating malaria is to reduce disease burden, the effects of treatment are generally ignored in estimates of the burden of malaria morbidity, which are usually presented in terms of numbers of clinical cases or episodes, with the main data sources being reports from health facilities and parasite prevalence surveys. The use of burden estimates that do not consider effects of treatment, leads to under-estimation of the impact of improvements in case management. Official estimates of burden very likely massively underestimate the impact of the roll-out of ACT as first-line therapy across Africa. This paper proposes a novel approach for estimating burden of disease based on the point prevalence of malaria attributable disease, or equivalently, the days with malaria fever in unit time. The technique makes use of data available from standard community surveys, analyses of fever patterns in malaria therapy patients, and data on recall bias. Application of this approach to data from Zambia for 2009-2010 gave an estimate of 2.6 (95% credible interval: 1.5-3.7) malaria attributable fever days per child-year. The estimates of recall bias, and of the numbers of days with illness contributing to single illness recalls, could be applied more generally. To obtain valid estimates of the overall malaria burden using these methods, there remains a need for surveys to include the whole range of ages of hosts in the population and for data on seasonality patterns in confirmed case series.

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Pattern of parasitaemia and febrile illness in a malaria therapy patient (Patient S-519).○: Parasite density; ▪ day with fever (core temperature > = 103°F).
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pone-0057297-g001: Pattern of parasitaemia and febrile illness in a malaria therapy patient (Patient S-519).○: Parasite density; ▪ day with fever (core temperature > = 103°F).

Mentions: Different issues arise in estimating how much morbidity is due to malaria from estimating the mortality burden (which accounts for most of the burden measured in terms of disability-adjusted life years (DALYs) [2]). This paper considers only morbidity. When promptly and effectively treated, malaria illness is of short duration, but if untreated, a single Plasmodium falciparum malaria infection can last for many months, causing recurring clinical attacks interspersed with asymptomatic periods [3] during which parasitaemia is often sub-patent. This can be clearly seen in the time courses of parasitaemia and fever observed among neurosyphilis patients treated with malaria therapy. In these studies, the full histories of many patients with untreated malaria infections were recorded following artificial inoculations of malaria parasites given for the purpose of clearing late stage syphilis infections [4]. Figure 1 shows the time pattern of parasitaemia and fever in a neurosyphilis patient treated with P. falciparum. In this figure, the single (untreated) infection gives rise to five periods of high parasitaemia. The first two of these are each associated with several bouts of fever indicated by the black bars at the top (see definitions in Table 1).


A novel approach for measuring the burden of uncomplicated Plasmodium falciparum malaria: application to data from Zambia.

Crowell V, Yukich JO, Briët OJ, Ross A, Smith TA - PLoS ONE (2013)

Pattern of parasitaemia and febrile illness in a malaria therapy patient (Patient S-519).○: Parasite density; ▪ day with fever (core temperature > = 103°F).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585385&req=5

pone-0057297-g001: Pattern of parasitaemia and febrile illness in a malaria therapy patient (Patient S-519).○: Parasite density; ▪ day with fever (core temperature > = 103°F).
Mentions: Different issues arise in estimating how much morbidity is due to malaria from estimating the mortality burden (which accounts for most of the burden measured in terms of disability-adjusted life years (DALYs) [2]). This paper considers only morbidity. When promptly and effectively treated, malaria illness is of short duration, but if untreated, a single Plasmodium falciparum malaria infection can last for many months, causing recurring clinical attacks interspersed with asymptomatic periods [3] during which parasitaemia is often sub-patent. This can be clearly seen in the time courses of parasitaemia and fever observed among neurosyphilis patients treated with malaria therapy. In these studies, the full histories of many patients with untreated malaria infections were recorded following artificial inoculations of malaria parasites given for the purpose of clearing late stage syphilis infections [4]. Figure 1 shows the time pattern of parasitaemia and fever in a neurosyphilis patient treated with P. falciparum. In this figure, the single (untreated) infection gives rise to five periods of high parasitaemia. The first two of these are each associated with several bouts of fever indicated by the black bars at the top (see definitions in Table 1).

Bottom Line: The use of burden estimates that do not consider effects of treatment, leads to under-estimation of the impact of improvements in case management.Official estimates of burden very likely massively underestimate the impact of the roll-out of ACT as first-line therapy across Africa.The estimates of recall bias, and of the numbers of days with illness contributing to single illness recalls, could be applied more generally.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.

ABSTRACT
Measurement of malaria burden is fraught with complexity, due to the natural history of the disease, delays in seeking treatment or failure of case management. Attempts to establish an appropriate case definition for a malaria episode has often resulted in ambiguities and challenges because of poor information about treatment seeking, patterns of infection, recurrence of fever and asymptomatic infection. While the primary reason for treating malaria is to reduce disease burden, the effects of treatment are generally ignored in estimates of the burden of malaria morbidity, which are usually presented in terms of numbers of clinical cases or episodes, with the main data sources being reports from health facilities and parasite prevalence surveys. The use of burden estimates that do not consider effects of treatment, leads to under-estimation of the impact of improvements in case management. Official estimates of burden very likely massively underestimate the impact of the roll-out of ACT as first-line therapy across Africa. This paper proposes a novel approach for estimating burden of disease based on the point prevalence of malaria attributable disease, or equivalently, the days with malaria fever in unit time. The technique makes use of data available from standard community surveys, analyses of fever patterns in malaria therapy patients, and data on recall bias. Application of this approach to data from Zambia for 2009-2010 gave an estimate of 2.6 (95% credible interval: 1.5-3.7) malaria attributable fever days per child-year. The estimates of recall bias, and of the numbers of days with illness contributing to single illness recalls, could be applied more generally. To obtain valid estimates of the overall malaria burden using these methods, there remains a need for surveys to include the whole range of ages of hosts in the population and for data on seasonality patterns in confirmed case series.

Show MeSH
Related in: MedlinePlus