MALARIA: Impact of national malaria control scale-up programmes in Africa: magnitude and attribution of effects

Richard W Steketee and Carlos C Campbell
Malaria Control and Evaluation Partnership in Africa
Malaria Journal 2010, 9:299doi:10.1186/1475-2875-9-299
27 October 2010
Background
Since 2005, malaria control scale-up has progressed in many African countries. Controlled studies of insecticide-treated mosquito nets (ITNs), indoor residual spraying (IRS), intermittent preventive treatment during pregnancy (IPTp) and malaria case management suggested that when incorporated into national programmes a dramatic health impact, likely more than a 20% decrease in all-cause childhood mortality, was possible. To assess the extent to which national malaria programmes are achieving impact the authors reviewed African country programme data available through 2009.
Methods
National survey data, published literature, and organization or country reports produced during 2000-2009 were reviewed to assess available malaria financing, intervention delivery, household or target population coverage, and reported health benefits including infection, illness, severe anaemia, and death.
Results
By the end of 2009, reports were available for ITN household ownership (n = 34) and IPTp use (n = 27) in malaria-endemic countries in Africa, with at least two estimates (pre-2005 and post-2005 intervals). Information linking IRS and case management coverage to impact were more limited. There was generally at least a three-fold increase in household ITN ownership across these countries between pre-2005 (median of 2.4% of households with at least one ITN) and post-2005 (median of 32.5% of households with at least one ITN). Ten countries had temporal data to assess programme impact, and all reported progress on at least one impact indicator (typically on mortality); in under-five year mortality rates most observed a decline of more than 20%. The causal relationship between malaria programme scale-up and reduced child illness and mortality rates is supported by biologic plausibility including mortality declines consistent with experience from intervention efficacy trials, consistency of findings across multiple countries and different epidemiologic settings, and temporal congruity where morbidity and mortality declines have been documented in the 18 to 36 months following intervention scale-up.
Conclusions
Several factors potentially have contributed to recent health improvement in African countries, but there is substantial evidence that achieving high malaria control intervention coverage, especially with ITNs and targeted IRS, has been the leading contributor to reduced child mortality. The documented impact provides the evidence required to support a global commitment to the expansion and long-term investment in malaria control to sustain and increase the health impact that malaria control is producing in Africa.
http://www.malariajournal.com/content/9/1/299

MALARIA: Control vs elimination - the great malaria debate

Photo: Wendy Stone/IRIN

Bed nets are a first step
1 November 2010 (IRIN) -
In 2007, Bill and Melinda Gates committed their foundation to eradicating malaria. It was, said Richard Feachem, director of the Global Health Group, part of the University of California, San Francisco, “a shock to the system for the malaria community, because for a couple of decades the ‘E’ words, eradication and elimination, were not used in polite company”.
That reticence was due to the very public failure of elimination campaigns, but the debate has been re-opened with the publication by the medical journal, The Lancet, of a special series on the subject.
The study sets out the real progress that has been made, assesses the chances for countries that might feel ready to try to eliminate all transmission within their borders, weighs up potential costs and benefits of elimination over control, and establishes research priorities for the tools that can make elimination possible.
The overall message is that malaria can be eliminated – indeed, has been wiped out in many places – but moving from control to elimination might not necessarily save money, or be quick or simple.
In 1945, the world malaria map was pretty much red all over, endemic almost everywhere except in the far north – Norway, Sweden, Iceland and Greenland, and in the Swiss alps. Now, 65 years later, the whole of Europe and North America is malaria free, as are Russia, Australia and some southerly parts of Latin America, as well as some islands, such as Mauritius.
The push to eliminate malaria is now going on along the borders of the world’s malaria zone, in North Africa and the Middle East, Central Asia, China and Central America. Morocco was certified malaria-free earlier this year; Turkmenistan just last week. Meanwhile, countries in Latin America and southern Africa are working to shrink the malaria zone in the south.
These are countries that have already achieved a high degree of malaria control, through vector control, the use of bed-nets, and effective diagnosis and treatment. Huge social and economic benefits have been realized. Children do not miss school; adults are no longer too debilitated to work.
Balancing act
Bruno Moonen, of the Clinton Health Access Initiative, says the decision to move from control to elimination is not as easy or as obvious as one might imagine. “When infection gets below 1 percent of the population, you have to make a choice. And you may choose to say, ‘We have almost no deaths and very few cases, and we can handle that’.”
He makes the point that elimination is much harder than control: all malaria cases have to be fully treated, including mild cases that might not normally have presented at a clinic. Then the sick person’s family and neighbours have to be screened, looking for people who have no symptoms but are carrying the parasite. Then they have to be treated with an aggressive drug regimen, even though they are not ill.
This is complicated by the fact that in most countries that could try to eliminate malaria, the predominant strain of the parasite is Plasmodium Vivax, which can lie dormant in the liver for years. Detection techniques for the dormant form are not totally effective, and the only drug available to eliminate them from the system – Primaquine – can cause a potentially fatal reaction in some people. Giving low doses over two weeks is safer, but raises compliance problems in healthy people who can see no obvious reason why they should be taking drugs at all. The Lancet identifies better tests for P Vivax and better drugs against the dormant form of the parasite as key research priorities.
And all this time control measures cannot be relaxed. As one of The Lancet contributors, Oliver Sabot, put it: “The moment you take your eye off the ball, malaria is going to come roaring back.” Even when a country is malaria-free, there still has to be surveillance to catch imported cases. Geoffrey Targett, of the London School of Tropical Medicine, said the UK still sees about 1,500 imported cases of malaria a year.
Sabot’s studies of Zanzibar, Mauritius, Swaziland and two areas of China indicate that elimination would probably be more expensive than low level control in most cases. Only Zanzibar showed a clear cost benefit, because its current control programme is already very expensive. His conclusion: “Someone considering elimination should not consider cost savings as one of the benefits.”
There may of course be other, less tangible benefits. Tourists may prefer to visit malaria-free Mauritius, for instance, rather than nearby Madagascar. There would also be a huge sense of accomplishment in being able to say a country had conquered the disease.
So is there a risk of governments embarking on elimination as a prestige project, without thinking through the implications? Feachem thinks there is, telling IRIN: “There are a number of malaria-endemic countries that have begun to speak about elimination in a way which is almost certainly premature… In our view they should do a feasibility study and be influenced by the mass of evidence, and for some of these ‘premature eliminators’, if they did such a study, they might retreat and say, ‘Not yet,’ not just because of their own situation but also because of their neighbours’.”
Even so, in the long term Feachem believes malaria can be conquered. “My guess,” he says, “would be 2050 or 2060. That would be a reasonable guess for complete eradication.”
http://www.irinnews.org/Report.aspx?Reportid=90938

MALARIA: Reducing Plasmodium falciparum Malaria Transmission in Africa: A Model-Based Evaluation of Intervention Strategies

Background. Half the world’s population is at risk of malaria, and every year nearly one million people—mainly children living in sub-Saharan Africa—die from this mosquito-borne parasitic disease. Most malarial deaths are caused by Plasmodium falciparum, which is transmitted to people by mainly night-biting Anopheles mosquitoes. When infected mosquitoes feed on people, they inject sporozoites, a parasitic form 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 more red blood cells. This increase in the parasitic burden causes malaria’s characteristic fever.
Infected red blood cells also release ‘‘gametocytes,’’ which infect mosquitoes when they take a blood meal. In the mosquito, the gametocytes multiply and develop into sporozoites, thus completing the parasite’s life cycle.
Malaria can be prevented by spraying the insides of houses (where most anopheles species feed and rest) with insecticides (indoor residual spraying, IRS) and by sleeping under bed nets that have been treated with long-lasting
insecticides (long-lasting insecticide nets, LLINs). Mass screening and treatment (MSAT) with effective antimalarial drugs can also reduce malaria transmission.
Why Was This Study Done? Early attempts to eradicate malaria (reduce its global incidence to zero) in the 1950s reduced the incidence of malaria to zero in some countries (malaria elimination) and greatly reduced malarial illnesses and
deaths in others (malaria control). However, this eradication program was aborted in the 1970s in part because of emerging drug and insecticide resistance. Recently, the advent of artemisinin-based combination therapies and new insecticides and the prospect of a malaria vaccine have renewed interest in
controlling, eliminating, and ultimately eradicating malaria.
Consequently, in September 2008, the Roll Back Malaria Partnership launched the Global Malaria Action Plan, which aims to reduce malaria deaths to near zero by 2015. But are the currently available tools for reducing malaria transmission
sufficient to control and eliminate malaria in Africa, the continent where most malaria deaths occur? In this study, the researchers use a new mathematical model of P. falciparum transmission to investigate this question.
What Did the Researchers Do and Find? The researchers’ P. falciparum transmission model consists of ‘‘compartments’’ through which individuals pass as they become infected with parasites, develop immunity, become
infectious to mosquitoes, and so on. The researchers used published data about parasite prevalence (the proportion of the population infected with parasites) and about relevant aspects of mosquito, parasite, and human biology, to
estimate the chances of an individual moving between compartments. Finally, they used the model to explore the impact over 25 years of increased coverage of LLINs, IRS, and MSAT, and of a future vaccine on malaria transmission in six
representative African settings. In a low-transmission setting, 80% coverage with LLINs reduced the parasite prevalence to below 1% in all age groups. In two moderate-transmission settings, LLIN scale-up alone failed to reach this target but the addition of IRS and MSAT drove the parasite prevalence below 1%. However, this combination of interventions did not control malaria in a moderate-transmission setting in which a mosquito species that bites and rests outside houses contributes to malaria transmission. Finally, in two hightransmission
settings, parasite prevalence could be driven below 1% only by setting unrealistic coverage targets for existing interventions.
What Do These Findings Mean? This new mathematical model greatly simplifies the complex dynamics of malaria transmission and includes several assumptions about which there is considerable uncertainty. The findings of this study are not, therefore, firm predictions of the future of malaria control in specific settings. Nevertheless, they suggest that it should be possible to make large reductions in malaria transmission and the associated disease burden in Africa over the next 25 years using currently available tools. Specifically, in regions where transmission is low or moderate and mosquitoes mainly feed indoors, it should be possible to reduce parasite prevalence to less than 1% provided a sustained intervention program is achieved. Importantly, however, these findings suggest that in regions where malaria transmission is high or where mosquitoes rest and bite outside houses, new approaches will be needed to control and eliminate malaria.

http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1000324