MALARIA: Mosquitoes score in chemical war

Declan Butler : 07 Jul 2011 : Nature
Key weapons in the fight against malaria, pyrethroid insecticides, are losing their edge. Over the past decade, billions of dollars have been spent on distributing long-lasting pyrethroid-treated bed nets and on indoor spraying. Focused in Africa, where most malaria deaths occur, these efforts have greatly reduced the disease's toll. But they have also created intense selection pressure for mosquitoes to develop resistance.
"Data are coming in thick and fast indicating increasing levels of resistance, and also of resistance in new places," says Jo Lines, an entomological epidemiologist and head of vector control at the Global Malaria Programme of the World Health Organization (WHO) in Geneva, Switzerland. The WHO now intends to launch a global strategy to tackle the problem by the end of the year.
Pyrethroids are the mainstay of malaria control because they are safe, cheap, effective and long-lasting. Alternatives such as organophosphates and carbamates are available for indoor spraying, although they cost more and are less effective. But pyrethroids are the only insecticides approved by the WHO for use in bed nets. "We have lots of our eggs in the pyrethroid basket," says Robert Newman, director of the Global Malaria Programme.
The international community has been slow to respond to the threat despite warnings, says Janet Hemingway, director of the Liverpool School of Tropical Medicine, UK, and chief executive of the non-profit Innovative Vector Control Consortium, a public-private venture set up in 2005 to develop new insecticides and monitoring tools. "A number of us had been banging the drums, saying: 'As soon as you scale up you are going to get resistance.'" But Lines says that the malaria-control community felt too many lives were at stake to let the threat of resistance stand in the way of massively scaling up the bed-net and spraying campaigns.
Teasing out the impact of resistance on the success of malaria-control interventions is difficult because so many other factors influence their outcome. More systematic and more sophisticated monitoring of resistance is also vital, says Lines. The best surveillance data (see 'Resistance on the rise'), although useful, do not give a complete picture of where resistance is emerging and how prevalent it is, he says. Malaria-control programmes often lack insect-resistance monitoring, and detection of all forms of resistance is not easy. Quick, cheap tests can pick out gene mutations that help the mosquitoes' nerve cells withstand pyrethroid attack. But other forms of resistance, which depend on increased levels of mosquito enzymes that can destroy pyrethroids before they reach their target, require more complex tests to detect (H. Ranson et al. Trends Parasitol. 27, 91-98; 2011).
But uncertainties about the extent of resistance or its impact are "no excuse for inaction", says Newman, arguing that the proposed WHO strategy needs to be urgently implemented, and also rolled out preemptively in places where resistance has yet to be detected. The WHO's plan will recommend, for example, that control programmes rotate insecticides sprayed indoors, using pyrethroids one year and a different class the next. This would be more costly and less effective than relying only on pyrethroids, however, so control programmes may be reluctant to adopt this measure.
Lines says that new combinations of insecticides also need to be developed, so that mosquitoes resistant to one would be killed by the other. In areas where pyrethroid bed nets are used, a different class of insecticides should be used for wall spraying, he adds.
Ultimately, entirely new classes of insecticides — particularly those that can be applied to bed nets — are needed to alleviate the dependence of malaria-control efforts on pyrethroids. For indoor spraying, some longer-lasting and more cost-effective non-pyrethroid insecticides should be available by next year, Hemingway says, although developing wholly new classes will take five to seven years. Repurposed agricultural insecticides might also act as a stopgap were resistance to pyrethroids to develop rapidly. Research targeting mosquito control is "grossly underfunded" compared with that on malaria drugs and vaccines, she adds, which is why control efforts have had so few options to call on.
http://www.nature.com/news/2011/050711/full/475019a.html

MALARIA: Senegal: Indoor spraying and US budget cuts

Michael Gerson : February 15, 2011

DAKAR, SENEGAL
For time beyond remembering, the people of Senegal have lost a battle with malaria, surrendering a portion of their children to fever, organ failure and death, until this terrible sacrifice seemed ordinary. The malaria-spreading mosquito is craftier than any beast of the field. After harvesting infected blood, it injects the malaria parasite in its next target. The developing parasites destroy red blood cells and overwhelm weak immune systems, particularly those of children.
But the mosquito has a weakness of its own. Once it draws blood, it must land to process its meal. If it stops on a wall sprayed with insecticide, or on a treated bed net, it dies, breaking the cycle of transmission.
A few years ago, Senegal began waking from its long malarial nightmare. It was the first African country to set the goal of universal bed net coverage, which it is likely to reach by the end of the year. It was the first to make widespread use of the rapid test for malaria, allowing an accurate diagnosis in 10 minutes. Senegal is conducting indoor spraying campaigns and providing effective, new combination drug treatments. Volunteers are going door to door in impoverished neighborhoods, instructing women in the proper use of nets.
The result? From 2005 to 2008, mortality among Senegalese children ages 6 and under dropped by a third, with reductions in malaria playing a major role. Some communities that had experienced 70 to 80 percent malaria prevalence during the high season of one year reported not a single case in the next.
It is a sophisticated, successful national effort. But it would not be possible without the help of the United States, provided through the Peace Corps, the President's Malaria Initiative and the Global Fund to Fight AIDS, Tuberculosis and Malaria.
As I was visiting hospitals and health huts in Senegal, I was also receiving e-mailed updates on House GOP budget cuts. The Global Fund, down 40 percent. Child survival programs, which include anti-malaria efforts, down 10 percent. AIDS relief, down 8 percent. Development assistance, down 30 percent.
These reductions were intended to be symbolic, but what do they symbolize? Fiscal responsibility? Hardly. No one can reasonably claim that the budget crisis exists because America spends too much on bed nets and AIDS drugs. Our massive debt is mainly caused by a combination of entitlement commitments, an aging population and health cost inflation. Claiming courage or credit for irrelevant cuts in foreign assistance is a net subtraction from public seriousness on the deficit.
So, do these cuts symbolize the Republican rejection of fuzzy-headed liberalism? Actually, the main initiatives on malaria and AIDS were created under Republican leadership. They emphasize measured outcomes and accountability. If the goal of House Republicans is to squander the Republican legacy on global health, they are succeeding.
Many American politicians, new to governing, have not been exposed to a uniquely modern historical challenge. Dramatically unequal global development has left one part of the world in possession of technologies and techniques that can save millions of lives in other parts of the world. These interventions are relatively simple and inexpensive - a bed net, a daily pill, a vaccination. Particularly for a nation dedicated to universal human rights, this mortality gap brings responsibilities. It has led America to make commitments on malaria, AIDS and other diseases that should be honored. But aiding the developing world also expands a certain type of global influence - winning friends, and perhaps opening markets, in unexpected places. Here in Senegal, this is the reason the Chinese government constructs stadiums, builds schools and provides malaria drugs.
For Americans, however, a proper understanding of our global duties requires some historical imagination. For 300 years, Goree Island here in Senegal was one of the main embarkation points of slaves sent to the New World. It is the location of the "door of no return," a stone opening to the Atlantic where many Africans saw the last of their homeland and their families. To the left of that door is a small cell where enslaved children were kept, really stacked, in conditions that ensured the death of many.
Now America is engaged in an effort to save the lives of Senegalese children - not out of guilt but because it better represents who we are. This historical symmetry is not just coincidence; it is more like providence. It demonstrates the kind of nation we have become, and must remain.
http://www.washingtonpost.com/wp-dyn/content/article/2011/02/14/AR2011021406184.html

MALARIA: evaluation of Indoor Residual Spraying

Indoor residual spraying for preventing malariaSpraying houses with insecticides (indoor residual spraying; IRS) to kill mosquitoes is one of the main methods that have been used to control malaria on a large scale. IRS has helped to eliminate malaria from great parts of Asia, Russia, Europe, and Latin America, and successful IRS programmes have also been run in parts of Africa.Another successful method of mosquito control relies on the use of physical barriers such as bednets or curtains that can also be sprayed with insecticides (insecticide treated nets; ITN). This review aims to look at the health benefits of IRS and to compare this method with ITNs.This review does not assess the potentially adverse effects of insecticides used for IRS, and it includes not only randomized controlled trials (RCTs), but also controlled before-and-after studies (CBA) and interrupted time series (ITS), as these methods were considered suitably rigorous.Six studies were identified for inclusion (four cluster RCTs, one CBA and one ITS). Four of these studies were conducted in sub-Saharan Africa, one in India and one in Pakistan. IRS reduced malaria transmission in young children by half compared to no IRS in Tanzania (an area where people are regularly exposed to malaria), and protected all age groups in India and Pakistan (where malaria transmission is more unstable and where more than one type of malaria is found). When compared with ITNs, IRS appeared more protective (according to the outcome chosen) in one trial conducted in an area of stable malaria transmission, but ITN seemed to be more protective than IRS in unstable areas. Unfortunately, the level of evidence is very limited and no firm conclusions should be drawn on the basis of this review.In conclusion, although IRS programmes have shown impressive success in malaria reduction throughout the world, there are too few well-run trials to be able to quantify the effects of IRS in areas with different malaria transmission, or to properly compare IRS and ITN. High-quality and long-duration trials on a large scale, done in areas where there has been little or no mosquito control are still urgently required. New trials should include an IRS arm and an ITN arm, and should also assess the combined effect of ITN and IRS, a very important question in view of malaria elimination.
http://onlinelibrary.wiley.com/o/cochrane/clsysrev/articles/CD006657/frame.html

MALARIA: Studies of Susceptibility of Mosquitoes to Insecticides Guide Malaria Interventions in Ethiopia

In Ethiopia, indoor residual spraying (IRS) of houses with insecticide has been one of the primary tools to prevent malaria transmission for more than 40 years. Entomological monitoring activities to study mosquito behavior and their susceptibility to insecticides were originally performed decades ago to inform IRS operations, but were discontinued due to insufficient funding and lack of trained manpower. PMI recently reintroduced these entomological monitoring activities as part of its support for IRS operations in Ethiopia.
Throughout 2009, PMI supported entomological monitoring activities at 11 sites in Oromia Regional State in order to determine and characterize the dominant mosquito species in the area, as well as test mosquitoes’ susceptibility to three classes of insecticides.

The findings from the entomological monitoring activities indicate that Anopheles arabiensis is the predominant malaria vector in Ethiopia and that this mosquito displays varying levels of susceptibility to the tested insecticides. Susceptibility to organochlorine insecticides such as DDT was shown to be low in all sites assessed, with only 0 to 35 percent of mosquitoes killed 24 hours after insecticide exposure. Susceptibility to pyrethroid and organophosphate insecticides was more variable (46 to 76 percent and 68 to 100 percent, respectively), however, and susceptibility to carbamate insecticides was shown to be high (96 to100 percent). The susceptibility to tested insecticides largely depended on prior insecticide use, with organochlorines and pyrethroids having been extensively used in previous IRS operations and in the agricultural sector, respectively.
Ethiopia is currently scaling up IRS activities as one of the interventions to eliminate malaria in the country. “The findings are crucial to ensure that future IRS operations will remain effective and will have the desired impact on malaria transmission,” says Alemayehu Getachew, focal person for PMI’s IRS implementing partner.
Along with its support for IRS operations in Oromia Regional State, PMI will continue to support entomological monitoring activities, as well as assist other in-country malaria stakeholders to expand monitoring activity into other regions of Ethiopia.
http://www.pmi.gov/news/voices/ethiopia_intervention.html

MALARIA: Burkina Faso, indoor spraying

OUAGADOUGOU, 2 June 2010 (IRIN) - Health teams are spraying homes with insecticide in the high-risk southwest, in Burkina Faso's first trial of the method to combat malaria. In 2009 the disease struck more than 20,000 people and killed 110 in the targeted district, according to the Health Ministry. Funded by the US Agency for International Development (USAID), the project is expected to cover 25,000 households in the district of Diébougou - using the insecticide bendiocarb - for one season at a cost of US$1.4 million.Indoor spraying should take place before the rainy season each year and cover most homes in endemic areas, but health workers say given the cost it is not yet clear when Burkina would be able to apply the method annually across the country. "For now only endemic areas can receive [indoor spraying] because of its cost," Patrice Combary, head of the national programme against malaria, told IRIN. USAID plans to treat Diébougou again next year, along with another district yet to be designated, according to Adama Koné, head of the indoor residual spraying project in Burkina. The World Health Organization (WHO) says indoor spraying is most effective when 80 percent of households in targeted areas are treated. WHO says the method, using DDT or other effective insecticides, should be included in national malaria control strategies where the proper conditions exist. "There must be sufficient capacity to deliver the intervention effectively, prevent unauthorized and un-recommended use of public health pesticides and manage insecticide resistance," WHO's Africa office says in a 2007 paper. Indoor spraying is seen as reinforcing existing measures - insecticide-treated bed nets and appropriate drugs for patients with probable or confirmed malaria. The government plans by end-June to distribute eight million treated bed nets - one net for every two people. Burkina registered some four million cases of malaria in 2009, according to the Health Ministry. In 2008 malaria struck 247 million people worldwide, killing one million, WHO says; most of the deaths were children in Africa. In Africa every 45 seconds a child dies of the disease.

MALARIA: Indoor Residual Spraying (IRS) Efiicacy

Indoor residual spraying of insecticides (IRS) is accepted as being an effective way of killing mosquitoes and of reducing rates of malaria transmission. IRS, using the insecticide DDT, is generally credited with much of the success achieved in eradicating malaria from several countries (mostly in the Americas and Europe) in the 1950s. It is now regarded as one of the key tools in efforts to control - and eventually eliminate - malaria in highly-endemic areas in Africa and Asia.But exactly how effective and how cost-effective is IRS? How does it compare in terms of effectiveness with other interventions to control malaria, in particular the use of insecticide-treated bednets (ITNs)? Such information would be helpful in policy and planning. A Cochrane systematic review, therefore, sought to find data that would enable the effectiveness of IRS to be quantified. The reviewers concluded, however, that insufficient research has so far been conducted to allow estimates to be made.The reviewers, from South Africa and from the Swiss Tropical and Public Health Institute, restricted their review to data from controlled studies. They looked for cluster randomized controlled trials (RCTs), controlled before-and-after studies (CBAs) and interrupted time series (ITS) that compared IRS to no IRS, or to ITNs. To be included in the review, studies had to contain information on pre-specified "key malariological parameters", such as case numbers, parasite prevalence, haemoglobin levels, and all-cause death rates in children under 10.Of 134 potentially relevant papers found in an electronic search, only six met the reviewers' inclusion criteria. Four were in sub-Saharan Africa and two in the Indian subcontinent. Three were in areas where malaria transmission is regarded as stable and three where it is unstable. Four were RCTs, one a CBA study and one an ITS. In four of the studies, the use of IRS was compared with no IRS and in three of them IRS was compared with ITNs.The reviewers note that from the studies that met their inclusion criteria there was, in particular, a lack of information such questions as the effectiveness of different types of insecticide and the impact of IRS on child mortality.The data from the included studies support the view that IRS is effective, but the number of studies was too low to properly quantify that effect. Most of the RCT data came from unstable malaria settings; evidence on the use of IRS in stable malaria settings was very limited. Some of the data suggested that ITNs give better protection than IRS in unstable areas but more trials are needed before any firm conclusions can be drawn.While data has been recorded from many programmes where IRS has been introduced, in the great majority of cases no control information is available for comparison. Consequently, such data was not part of this review. Interviewed by Science Daily one of the review team, Professor Christian Lengeler, said, "Clearly, this is disappointing. With such a large body of evidence it is sad that so few of the studies provide high-quality scientific evidence. This represents a great waste of resources and efforts, and we are left with a very poor evidence base".Speaking of the research that is now needed, Professor Lengeler said, "Because we know that IRS works, it is no longer ethically possible to carry out studies with control groups that don't receive anything. Consequently, we urgently need more high-quality studies that compare IRS with the other widely implemented vector control method, ITNs".
http://www.fightingmalaria.org/news.aspx?id=1440

MALARIA: Angola

At least 35 million dollars is the amount made available annually by the United States government to support programmes of fight against malaria in Angola, on Monday in Central Huambo Province, said the US ambassador to this African country, Dan Mozena.
Speaking at the end of a two-day working visit to Huambo, Dan Mozena said that measures in the fight against malaria comprise indoor residual spraying, distribution of mosquito nets and medicines.
According to the diplomat, due to this fund, mortality rate by malaria has reduced in Angolaover the last five years.
http://www.portalangop.co.ao/motix/en_us/noticias/saude/2010/3/17/United-States-grants-USD-million-for-fight-against-malaria,09c9cdb8-52fa-4f7f-acab-ddd837418bb0.html