Nearly 200 Million Africans at Risk for Malaria

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New research shows that after 10 years of intensified campaigns against malaria 184-million people in Africa still live in moderate to high-risk areas. While the number is high, it’s down from nearly 220-million in 2000 when anti-malaria efforts began to increase.

The findings are based on thousands of community-based surveys in 44 African countries and territories. These are places where malaria has been endemic.

Dr. Abdisalan Noor, co-leader of the team that conducted the research, said, “What we are looking at, first of all, is to try and estimate the level of infection with malaria in African communities. This doesn’t necessarily mean the number of people who die of malaria, but the proportion of people who are likely to carry the most virulent type of the malaria parasite. That’s Plasmodium falciparum.”

Noor and co-leader Professor Robert Snow are with the Kenya Medical Research Institute-Wellcome Trust Research Program. The team also included researchers from Oxford University and the World Health Organization.

The study reflects the effects of the Roll Back Malaria campaign and other programs. The campaign brought together many multi-lateral, private and non-governmental organizations. The goal was to cut in half the number of deaths from malaria by 2010. It had a shaky start and was criticized in its early years for a lack of progress.

Dr. Noor said that the new study finds a mix of good and bad news about efforts to combat malaria.

“The positive news is there has been production in 40 of the 44 African countries for which we were able to estimate change. There has been some reduction in the proportion of people who are likely to be affected with the falciparum parasite. About 218-million people in 2010 lived in areas where transmission – malaria transmission – had dropped by at least one level of endemicity. So that’s good news.”

Endemicity is described as the measure of disease prevalence in a region.

“The other side of it.” said Noor, “is that despite all these gains almost 60 percent of African populations still live in areas where more than 10-percent of the population is likely to carry the malaria parasite. And out of these about 184-million people live in areas where more than 50-percent of the population are likely to carry malaria infections.”

Among the countries where disease transmission remained high or unchanged are DRC, Uganda, Malawi and South Sudan.

Despite the large number of people still likely to be infected, Noor says he does not want to detract from the gains made by the international community – namely, the reduction in risk for 34-million people from 2000 to 2010.

“We haven’t actually looked at the reasons why some places are more resilient to change than others. Epidemiologically, it’s got something to do with the higher the starting transmission, the longer it takes to bring down the disease,” he said.

Another reason, he said, may be weak health care systems in many countries. It can be difficult to get reliable estimates on how many people get sick or die from malaria. Noor says stronger health care systems would play a major role in reducing infection risk.

In the 10-year period studied, funding for malaria programs steadily increased from 100-million-dollars to two-billion dollars a year.

He said, “It’s no news that despite all this investment we need more. I think the estimate for the needs for malaria control in Africa is around five-billion dollars if we look at the last global malaria action plan.”

Noor said that there’s a lot to be proud of in the global community in terms of reducing malaria cases.

He added that despite a recent global recession — and competing priorities — resources for malaria campaigns should not only be sustained, but increased. That would help bring malaria to a point where, he said, it would be of “minimal public significance.”

Right now, though, the Roll Back Malaria campaign estimates a child dies every 60 seconds from the disease.

 

Source: VOA News

G6PD Deficiency Prevalence and Estimates of Affected Populations in Malaria Endemic Countries

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Primaquine is a key drug for malaria elimination. In addition to being the only drug active against the dormant relapsing forms of Plasmodium vivax, primaquine is the sole effective treatment of infectious P. falciparum gametocytes, and may interrupt transmission and help contain the spread of artemisinin resistance. However, primaquine can trigger haemolysis in patients with a deficiency in glucose-6-phosphate dehydrogenase (G6PDd). Poor information is available about the distribution of individuals at risk of primaquine-induced haemolysis. We present a continuous evidence-based prevalence map of G6PDd and estimates of affected populations, together with a national index of relative haemolytic risk.

Methods and Findings

Representative community surveys of phenotypic G6PDd prevalence were identified for 1,734 spatially unique sites. These surveys formed the evidence-base for a Bayesian geostatistical model adapted to the gene’s X-linked inheritance, which predicted a G6PDd allele frequency map across malaria endemic countries (MECs) and generated population-weighted estimates of affected populations. Highest median prevalence (peaking at 32.5%) was predicted across sub-Saharan Africa and the Arabian Peninsula. Although G6PDd prevalence was generally lower across central and southeast Asia, rarely exceeding 20%, the majority of G6PDd individuals (67.5% median estimate) were from Asian countries. We estimated a G6PDd allele frequency of 8.0% (interquartile range: 7.4–8.8) across MECs, and 5.3% (4.4–6.7) within malaria-eliminating countries. The reliability of the map is contingent on the underlying data informing the model; population heterogeneity can only be represented by the available surveys, and important weaknesses exist in the map across data-sparse regions. Uncertainty metrics are used to quantify some aspects of these limitations in the map. Finally, we assembled a database of G6PDd variant occurrences to inform a national-level index of relative G6PDd haemolytic risk. Asian countries, where variants were most severe, had the highest relative risks from G6PDd.

Conclusions

G6PDd is widespread and spatially heterogeneous across most MECs where primaquine would be valuable for malaria control and elimination. The maps and population estimates presented here reflect potential risk of primaquine-associated harm. In the absence of non-toxic alternatives to primaquine, these results represent additional evidence to help inform safe use of this valuable, yet dangerous, component of the malaria-elimination toolkit.

Background

Malaria is a parasitic infection that is transmitted to people through the bites of infected mosquitoes. Of the four parasites that cause malaria, Plasmodium falciparum is the most deadly and P. vivax is the commonest and most widely distributed. Malaria parasites have a complex life cycle. Infected mosquitoes inject “sporozoites” into people, a form of the parasite that replicates inside human liver cells. After a few days, the liver cells release “merozoites,” which invade red blood cells where they replicate rapidly before bursting out and infecting other red blood cells. This increase in the parasitic burden causes malaria’s characteristic fever and can cause organ damage and death. Infected red blood cells also release “gametocytes,” which infect mosquitoes when they take a blood meal. In the mosquito, gametocytes multiply and develop into sporozoites, thus completing the parasite’s life cycle. Malaria can be prevented by controlling the mosquitoes that spread the parasite and by avoiding mosquito bites by sleeping under insecticide-treated bed nets. Treatment with effective antimalarial drugs also decreases malaria transmission.

Why Was This Study Done?

The Global Malaria Action Plan aims to reduce malaria deaths to zero by 2015 and to eradicate malaria in the long-term through its progressive elimination in malaria-endemic countries (countries where malaria is always present). Primaquine is a key drug for malaria elimination. It is the only treatment effective against the gametocytes that transmit malaria between people and mosquitoes and against P. vivax “hypnozoites,” which hibernate in the liver and cause malaria relapses. Unfortunately, primaquine induces mild to severe destruction of red blood cells (hemolysis) in people who have a deficiency in the enzyme glucose-6-phosphate dehydrogenase (G6PD). G6PD deficiency (G6PDd) is common in some ethnic groups but the global distribution of individuals at risk of primaquine-induced hemolysis is unknown and there is no practical field test for G6PDd. Consequently, it is hard to design and implement primaquine treatment practices that balance the benefits of malaria transmission reduction and relapse prevention against the risk of hemolysis. Here, the researchers use a geostatistical model to map the prevalence (frequency in a population) of G6PDd in malaria-endemic countries and to estimate how many people are affected in these countries. They also develop a national index of relative hemolytic risk.

What Did the Researchers Do and Find?

The researchers fed data from community surveys of the prevalence of phenotypic G6PDd (reduced enzyme activity) for 1,734 sites (including 1,289 sites in malaria-endemic countries) into a geostatistical model originally developed to map global malaria endemicity. The model predicted that G6PDd is widespread across malaria-endemic regions, with the lowest prevalences in the Americas and the highest in tropical Africa and the Arabian Peninsula, but that most G6PDd individuals live in Asian countries. The predicted prevalence of G6PDd varied considerably over relatively short distances in many areas but, averaged across malaria-endemic countries it was 8%, which corresponds to about 350 million affected individuals; averaged across countries that are currently planning for malaria elimination, the prevalence was 5.3% (nearly 100 million affected individuals). Finally, the researchers used data on the geographical occurrence of G6PD variants classified according to their enzyme activity levels as mild or severe to derive an index of hemolytic risk from G6PDd for each malaria-endemic country. The greatest risk was in the Arabian Peninsula and west Asia where the predicted prevalence of G6PDd and the occurrence of severe G6PD variants were both high.

What Do These Findings Mean?

These findings suggest that G6PDd is widespread and spatially heterogeneous across most of the malaria-endemic countries where primaquine would be valuable for malaria control and elimination. The accuracy of these findings is limited, however, by the assumptions made in the geostatistical model, by the accuracy of the data fed into the model, and by the lack of data for some malaria-endemic countries. Moreover, there is considerable uncertainty associated with the proposed index of hemolysis risk because it is based on phenotypic G6PDd enzyme activity classifications, which is presumed, but not widely demonstrated, to be a surrogate marker for hemolysis. Nevertheless, these findings pave the way for further data collection and for the refinement of G6PDd maps that, in the absence of non-toxic alternatives to primaquine, will guide the design of safe primaquine regimens for the elimination of malaria.

Citation: Howes RE, Piel FB, Patil AP, Nyangiri OA, Gething PW, et al. (2012) G6PD Deficiency Prevalence and Estimates of Affected Populations in Malaria Endemic Countries: A Geostatistical Model-Based Map. PLoS Med 9(11): e1001339. doi:10.1371/journal.pmed.1001339

Academic Editor: Lorenz von Seidlein, Menzies School of Health Research, Australia

Received: February 22, 2012; Accepted: October 4, 2012; Published: November 13, 2012

Funding: This work was supported by a Wellcome Trust Biomedical Resources Grant (#085406), which funded REH, FBP, OAN, and MMH; SIH is funded by a Senior Research Fellowship from the Wellcome Trust (#095066) that also supports PWG and KEB; APP was funded by a Biomedical Resources Grant from the Wellcome Trust (#091835). MD is funded by the Oxford University-Li Ka Shing Foundation Global Health Programme. This work forms part of the output of the Malaria Atlas Project (MAP), principally funded by the Wellcome Trust, UK. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: G6PDd, glucose-6-phosphate dehydrogenase deficiency; GRUMP, Global Rural-Urban Mapping Project; IQR, interquartile range; MEC, malaria endemic country; PPD, posterior predictive distribution; UN, United Nations; WHO, World Health Organization

Full Article: G6PD Deficiency Prevalence and Estimates of Affected Populations in Malaria Endemic Countries: A Geostatistical Model-Based Map (PDF)

Copyyight © 2012 Rosalind E. Howes, Frédéric B. Piel, Anand P. Patil, Oscar A. Nyangiri, Peter W. Gething, Mewahyu Dewi, Mariana M. Hogg, Katherine E. Battle, Carmencita D. Padilla, J. Kevin Baird, Simon I. Hay

This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Mobile Phone Text Messaging: Tool for Malaria Control in Africa

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Across many malaria-endemic areas in rural Africa, the communication gap between managers, health workers, and patients is a significant barrier to efficient malaria control. The rapid expansion of mobile network coverage and the widespread availability of basic handsets have the potential to substantively bridge the communication gap. Text messaging, as the least-expensive mobile phone function found on all handsets, could improve the delivery of health services and health outcomes.

Six major areas of malaria control in which deficiencies are apparent and text messaging interventions could be beneficial are:

  1. Disease and treatment effectiveness surveillance
  2. Monitoring of the availability of health commodities
  3. Pharmacovigilance and post-marketing surveillance of the safety and quality of antimalarial drugs
  4. Health worker adherence to guidelines
  5. Patient adherence to medication regimen
  6. Post-treatment review

Text messages transmitting information from the periphery of the health systems to malaria control managers are in the first three malaria control areas: (1) disease and treatment effectiveness surveillance, (2) monitoring of the availability of health commodities, and (3) pharmacovigilance and post-marketing surveillance of the safety and quality of antimalarial medicines. Future projects in these three areas should demonstrate responses to data signals and comparative advantages with routine information systems.

Text messages in the second three areas transmit information to health workers and patients to support the management of malaria patients by improving (4) health workers’ adherence to guidelines, (5) patient adherence to medicines, and (6) post-treatment review. Future priorities in these areas are cost-effectiveness evaluations, qualitative research, and studies measuring impact on the processes of care and health outcomes.


Funding: DZ is supported by the Wellcome Trust project grant [#084253]. RWS is supported by the Wellcome Trust as Principal Research Fellow [#079080]. AOT is supported by the Worldwide Antimalarial Resistance Network (WWARN) through a Bill & Melinda Gates Foundation grant [#48807.01]. All authors acknowledge support from the Wellcome Trust core grant [#092654/Z/10/A]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Citation: Zurovac D, Talisuna AO, Snow RW (2012) Mobile Phone Text Messaging: Tool for Malaria Control in Africa. PLoS Med 9(2): e1001176. doi:10.1371/journal.pmed.1001176

Copyright: © 2012 Zurovac et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Full Article: Mobile Phone Text Messaging: Tool for Malaria Control in Africa (PDF)

 

Counterfeit Anitmalarial Drugs Threaten Crisis in Africa

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Hopes of at last controlling malaria in Africa could be dashed by the emergence of poor-quality and fraudulent antimalarial medicines, warn experts writing in Malaria Journal. Unless urgent action is taken both within Africa and internationally, they argue, millions of lives could be put at risk. [Read more…]

Monkeys Provide Malaria Reservoir for Human Disease in South-East Asia

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Macaque Monkey

Juvenile Macaque - Sandakan, Malaysia. Photo by Frances Williams (Sandakan-Travel.com).

Monkeys infected with an emerging malaria strain are providing a reservoir for human disease in Southeast Asia, according to recent research. The study confirms that the species has not yet adapted to humans and that monkeys are the main source of infection.

Malaria is a potentially deadly disease that kills over a million people each year. The disease is caused by malaria parasites, which are transmitted by infected mosquitoes and injected into the bloodstream.

There are five species of malaria parasite that are known to cause disease in humans, of which Plasmodium knowlesi is the most recently identified. Previously thought to only infect monkeys, researchers have shown that human P. knowlesi infections are widely distributed in Southeast Asia and that it is a significant cause of malaria in Malaysian Borneo. Until now, it was not clear whether the infection is transmitted from person to person, or is passed over from infected monkeys.

Researchers led by Professor Balbir Singh at the Malaria Research Centre, Universiti Malaysia Sarawak, collaborating with Sarawak State Health Department, St George’s University of London and the London School of Hygiene and Tropical Medicine, examined blood samples from 108 wild macaques from different locations around the Sarawak division in Malaysian Borneo. Their results reveal that 78% were infected with the P. knowlesi species of malaria parasite, and many were infected with one or more of four other species of monkey malaria parasites that have not yet been found in humans.

By comparing the molecular identity of the parasites from monkeys and those isolated from patients with knowlesi malaria, the team were able to build a picture of the evolutionary history of the parasite and its preferred host. Their analysis reveals that transmission of the knowlesi species is more common amongst wild monkeys, than from monkeys to humans, and that monkeys remain the dominant host.

“Our findings strongly indicate that P. knowlesi is a zoonosis in this area, that is to say it is passed by mosquitoes from infected monkeys to humans, with monkeys acting as a reservoir host,” explains Professor Singh. “However, with deforestation threatening the monkeys’ habitat and increases in the human population, it’s easy to see how this species of malaria could switch to humans as the preferred host. This would also hamper current efforts aimed at eliminating malaria.”

Based on the molecular data, the researchers estimate that the knowlesi malaria species evolved from its ancestral species between 98 000 and 478 000 years ago. This predates human settlement in the area, meaning that monkeys are mostly likely to have been the initial host for the parasite when the species first emerged. This estimate also indicates that the species is as old as, or older than, the two most common human malaria parasites, P. falciparum and P. vivax.

The study was funded by the Wellcome Trust, a global charitable foundation that supports biomedical research and the medical humanities. It was published today in the journal PLoS Pathogens.

Source: The Wellcome Trust