Malaria in sub-Saharan Africa

An insecticide-treated bed-net campaign and childhood malaria in Burkina Faso

OBJECTIVE

To investigate if the first national insecticide-treated bed-net campaign in Burkina Faso, done in 2010, was followed by a decrease in childhood malaria in a district with high baseline transmission of the disease.

METHODS

We obtained data on the prevalence of Plasmodium falciparum parasitaemia in children aged 2 weeks to 36 months from malaria surveys in 2009 and 2011. We assessed morbidity in children younger than 5 years by comparing data from the Nouna health district's health management information system before and after the campaign in 2010. We analysed mortality data from 2008 to 2012 from Nouna's health and demographic surveillance system.

FINDINGS

The bed-net campaign was associated with an increase in the reported use of insecticide-treated nets. In 2009, 73% (630/869) of children reportedly slept under nets. In 2011, 92% (449/487) did. The campaign had no effect on the proportion of young children with P. falciparum parasitaemia after the rainy season; 52% (442/858) in 2009 and 53% (263/499) in 2011. Cases of malaria increased markedly after the campaign, as did the number of children presenting with other diseases. The campaign was not associated with any changes in child mortality.

CONCLUSION

The 2010 insecticide-treated net campaign in Burkina Faso was not associated with a decrease in care-seeking for malaria or all-cause mortality in children younger than 5 years. The most likely explanation is the high coverage of nets in the study area before the campaign which could have had an effect on mosquito vectors, limiting the campaign's impact.

Efficacy and safety of triple combination therapy with artesunate-amodiaquine-methylene blue for falciparum malaria in children: a randomized controlled trial in Burkina Faso

BACKGROUND

Methylene blue (MB) has been shown to be safe and effective against falciparum malaria in Africa and to have pronounced gametocytocidal properties.

METHODS

Three days of treatment with artesunate (AS)-amodiaquine (AQ) combined with MB was compared with AS-AQ treatment in a randomized controlled phase IIb study; the study included 221 children aged 6-59 months with uncomplicated falciparum malaria in Burkina Faso. The primary end point was gametocyte prevalence during follow-up, as determined by microscopy and real-time quantitative nucleic acid sequence-based amplification (QT-NASBA).

RESULTS

The gametocyte prevalence of Plasmodium falciparum at baseline was 3.6% (microscopy) and 97% (QT-NASBA). It was significantly lower in the AS-AQ-MB than in the AS-AQ group on day 7 of follow-up (microscopy, 1.2% vs 8.9% [P < .05]; QT-NASBA, 36.7% vs 63.3% [P < .001]). Hemoglobin values were significantly lower in the AS-AQ-MB group than in the AS-AQ group at days 2 and 7 of follow-up. Vomiting of the study medication occurred significantly more frequently in the AS-AQ-MB group.

CONCLUSIONS

The combination of MB with an artemisinin-based combination therapy has been confirmed to be effective against the gametocytes of P. falciparum. MB-based combinations need to be compared with primaquine-based combinations, preferably using MB in an improved pediatric formulation. Clinical Trials Registration: NCT01407887.

Symptomatic malaria diagnosis overestimate malaria prevalence, but underestimate anaemia burdens in children: results of a follow up study in Kenya

BACKGROUND

The commonly accepted gold standard diagnostic method for detecting malaria is a microscopic reading of Giemsa-stained blood films. However, symptomatic diagnosis remains the basis of therapeutic care for the majority of febrile patients in malaria endemic areas. This study aims to compare the discrepancy in malaria and anaemia burdens between symptomatic diagnosed patients with those diagnosed through the laboratory.

METHODS

Data were collected from Western Kenya during a follow-up study of 887 children with suspected cases of malaria visiting the health facilities. In the laboratory, blood samples were analysed for malaria parasite and haemoglobin levels. Differences in malaria prevalence between symptomatic diagnosis and laboratory diagnosis were analysed by Chi-square test. Bayesian probabilities were used for the approximation of the malaria and anaemia burdens. Regression analysis was applied to: (1) determine the relationships between haemoglobin levels, and malaria parasite density and (2) relate the prevalence of anaemia and the prevalence of malaria.

RESULTS

The prevalence of malaria and anaemia ranged from 10% to 34%, being highest during the rainy seasons. The predominant malaria parasite was P. falciparum (92.3%), which occurred in higher density in children aged 2‒5 years. Fever, high temperature, sweating, shivering, vomiting and severe headache symptoms were associated with malaria during presumptive diagnosis. After conducting laboratory diagnosis, lower malaria prevalence was reported among the presumptively diagnosed patients. Surprisingly, there were no attempts to detect anaemia in the same cohort. There was a significant negative correlation between Hb levels and parasite density. We also found a positive correlation between the prevalence of anaemia and the prevalence of malaria after laboratory diagnosis indicating possible co-occurrence of malaria and anaemia.

CONCLUSION

Symptomatic diagnosis of malaria overestimates malaria prevalence, but underestimates the anaemia burden in children. Good clinical practice dictates that a laboratory should confirm the presence of parasites for all suspected cases of malaria.

Changing patterns of malaria epidemiology between 2002 and 2010 in Western Kenya: the fall and rise of malaria

Background

The impact of insecticide treated nets (ITNs) on reducing malaria incidence is shown mainly through data collection from health facilities. Routine evaluation of long-term epidemiological and entomological dynamics is currently unavailable. In Kenya, new policies supporting the provision of free ITNs were implemented nationwide in June 2006. To evaluate the impacts of ITNs on malaria transmission, we conducted monthly surveys in three sentinel sites with different transmission intensities in western Kenya from 2002 to 2010.

Methods and Findings

Longitudinal samplings of malaria parasite prevalence in asymptomatic school children and vector abundance in randomly selected houses were undertaken monthly from February 2002. ITN ownership and usage surveys were conducted annually from 2004 to 2010. Asymptomatic malaria parasite prevalence and vector abundances gradually decreased in all three sites from 2002 to 2006, and parasite prevalence reached its lowest level from late 2006 to early 2007. The abundance of the major malaria vectors, Anopheles funestus and An. gambiae, increased about 5–10 folds in all study sites after 2007. However, the resurgence of vectors was highly variable between sites and species. By 2010, asymptomatic parasite prevalence in Kombewa had resurged to levels recorded in 2004/2005, but the resurgence was smaller in magnitude in the other sites. Household ITN ownership was at 50–70% in 2009, but the functional and effective bed net coverage in the population was estimated at 40.3%, 49.4% and 28.2% in 2010 in Iguhu, Kombewa, and Marani, respectively.

Conclusion

The resurgence in parasite prevalence and malaria vectors has been observed in two out of three sentinel sites in western Kenya despite a high ownership of ITNs. The likely factors contributing to malaria resurgence include reduced efficacy of ITNs, insecticide resistance in mosquitoes and lack of proper use of ITNs. These factors should be targeted to avoid further resurgence of malaria transmission.

Molecular epidemiology of Plasmodium species prevalent in Yemen based on 18 s rRNA

Background

Malaria is an endemic disease in Yemen and is responsible for 4.9 deaths per 100,000 population per year and 43,000 disability adjusted life years lost. Although malaria in Yemen is caused mainly by Plasmodium falciparum and Plasmodium vivax, there are no sequence data available on the two species. This study was conducted to investigate the distribution of the Plasmodium species based on the molecular detection and to study the molecular phylogeny of these parasites.

Methods

Blood samples from 511 febrile patients were collected and a partial region of the 18 s ribosomal RNA (18 s rRNA) gene was amplified using nested PCR. From the 86 positive blood samples, 13 Plasmodium falciparum and 4 Plasmodium vivax were selected and underwent cloning and, subsequently, sequencing and the sequences were subjected to phylogenetic analysis using the neighbor-joining and maximum parsimony methods.

Results

Malaria was detected by PCR in 86 samples (16.8%). The majority of the single infections were caused by P. falciparum (80.3%), followed by P. vivax (5.8%). Mixed infection rates of P. falciparum + P. vivax and P. falciparum + P. malariae were 11.6% and 2.3%, respectively. All P. falciparum isolates were grouped with the strain 3D7, while P. vivax isolates were grouped with the strain Salvador1. Phylogenetic trees based on 18 s rRNA placed the P. falciparum isolates into three sub-clusters and P. vivax into one cluster. Sequence alignment analysis showed 5-14.8% SNP in the partial sequences of the 18 s rRNA of P. falciparum.

Conclusions

Although P. falciparum is predominant, P. vivax, P. malariae and mixed infections are more prevalent than has been revealed by microscopy. This overlooked distribution should be considered by malaria control strategy makers. The genetic polymorphisms warrant further investigation.

[Subsidized artemisinin based combination treatments for Africa]

Malaria-associated mortality and morbidity have increased in recent decades, with the worldwide spread of chloroquine and sulfadoxine-pyrimethamine resistant parasites. Artemisinin-based combination therapies (ACTs) have been proposed as an alternative to conventional antimalarial drugs. ACTs are effective against multidrug-resistant infections, work quickly, are safe and well tolerated, and seem to decrease transmission by inactivating gametocytes. The affordable medicines facility-malaria (AMFm) - an initiative aiming at increasing the availability of affordable ACTs through public and private practice - is trying to accelerate the large-scale use of ACT worldwide. This began with an initial pilot phase in a selected group of African countries. However, the epidemiology of malaria, the economic context, and healthcare infrastructure of African countries differ considerably from those prevailing in Asia, where ACTs were first implemented in the 1990s. ACT implementation in Africa must therefore be accompanied by control and operational measures to maintain the efficacy of ACT and to protect patients against misuse. We discuss the expected benefits of the AMFm initiative in Africa and stress the importance of dealing with operational issues before implementation in the field, focusing particularly on drug resistance.

Changes in the burden of malaria in sub-Saharan Africa

The burden of malaria in countries in sub-Saharan Africa has declined with scaling up of prevention, diagnosis, and treatment. To assess the contribution of specific malaria interventions and other general factors in bringing about these changes, we reviewed studies that have reported recent changes in the incidence or prevalence of malaria in sub-Saharan Africa. Malaria control in southern Africa (South Africa, Mozambique, and Swaziland) began in the 1980s and has shown substantial, lasting declines linked to scale-up of specific interventions. In The Horn of Africa, Ethiopia and Eritrea have also experienced substantial decreases in the burden of malaria linked to the introduction of malaria control measures. Substantial increases in funding for malaria control and the procurement and distribution of effective means for prevention and treatment are associated with falls in malaria burden. In central Africa, little progress has been documented, possibly because of publication bias. In some countries a decline in malaria incidence began several years before scale-up of malaria control. In other countries, the change from a failing drug (chloroquine) to a more effective drug (sulphadoxine plus pyrimethamine or an artemisinin combination) led to immediate improvements; in others malaria reduction seemed to be associated with the scale-up of insecticide-treated bednets and indoor residual spraying.

Access to malaria treatment in young children of rural Burkina Faso

Background

Effective and timely treatment is an essential aspect of malaria control, but remains a challenge in many parts of sub-Saharan Africa. The objective of this study was to describe young children's access to malaria treatment in Nouna Health District, Burkina Faso.

Methods

In February/March 2006, a survey was conducted in a representative sample of 1,052 households.

Results

Overall 149/1052 (14%) households reported the current possession of anti-malarial medicine, which was significantly associated with urban area, literacy of household head, having young children, and high socio-economic status. Out of a total of 802 children under five years, at least one malaria episode was reported for 239 (30%) within the last month. Overall 95% of children received treatment, either modern (72%), traditional (18%) or mixed (5%). Most of the medicines were provided as home treatment by the caregiver and half of children received some type of modern treatment within 24 hours of the occurrence of first symptoms. Despite a recent policy change to artemisinin-based combination therapy, modern anti-malarials consisted mainly of chloroquine (93%). Modern drugs were obtained more often from a health facility in localities with a health facility compared to those without (60% vs. 25.6%, p < 0.001). In contrast, beside informal providers, volunteer community health workers (CHW) were the main source of modern medicine in localities without a health centre (28% vs. 3%, p < 0.001).

Conclusion

Access to modern health services providing quality controlled effective combination therapies against malaria needs to be strengthened in rural Africa, which should include a re-investigation of the role of CHW 30 years after Alma Ata.

Decreasing childhood mortality and increasing proportion of malaria deaths in rural Burkina Faso

BACKGROUND

Malaria is the leading cause of death among children less than five years of age in sub-Saharan Africa (SSA), however, precise estimates on the burden of malaria are lacking. The aim of this study was to describe temporal trends for malaria and all-cause mortality by combining a series of clinical and intervention studies conducted in Burkina Faso.

METHODS

Data from a demographic surveillance system was used to follow-up children under five years who participated in five observational and intervention studies between June 1999 and December 2004 in rural north-western Burkina Faso. Mortality data was analyzed with cause-specific mortality ascertained using the verbal autopsy method. Person-years (PY) of observations were computed and age-standardized mortality rates (MR) for all-causes and malaria (adjusted for missing causes of death) were calculated. Rate ratios to investigate mortality variations over years were calculated using multivariate Poisson regression.

RESULTS

The study followed 6,387 children aged less than five years (mean follow-up: 2.8 years; 16,099 PY). During the study period, 443 deaths were registered with malaria accounting for 49% of all deaths. All-cause and malaria-specific MR were 26.7 (95% CI: 24.2-29.2) and 15.8 (95% CI: 14.217.7) per 1,000 PY. All-cause MR declined over years of follow-up (from 31.2 to 16.3 per 1,000 PY in 1999/2000 to 2004, respectively) but malaria MR remained relatively stable (from 15.8 to 12.1 per 1,000 PY in 1999/2000 to 2004, respectively) resulting in an increasing relative effect of malaria on all-cause mortality. Variations in all-cause and malaria-specific mortality were observed with increasing age and across village town clusters.

CONCLUSION

The findings of this study support the continuously decreasing trend of all-cause mortality in most of SSA, but call for more efforts to comprehensively address malaria with existing control tools such as insecticide-treated bed nets and effective first-line combination therapies.