“They found that mosquitoes seemed to change their hours of “peak aggression” from 2 or 3 a.m. to around 5 a.m. three years after nets were put up. And in one village, the proportion of mosquito bites inflicted outdoors rose.
Posts Tagged ‘Mosquito net’
Published online 5 July 2011 | Nature 475, 19 (2011) | doi:10.1038/475019a
Mosquitoes score in chemical war
Growing resistance is threatening global malaria-control efforts.
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.
Amid all the gloomy talk of economic recession and dire warnings that the amount of money available for development aid is going to shrink, a report on the state of malaria research out on Tuesday is refreshingly upbeat. Investment has more than quadrupled in the past 16 years, it says, from $121m in 1993 to $612m in 2009. Yes, malaria is a massive health burden in many countries and was neglected for decades. But, it goes on – and this is worth quoting because it’s a rare moment of good news:
Fortunately, a dramatic increase in support for R&D since the mid-1990s means funders are now well on the way to achieving global malaria control, treatment and elimination goals and, with maintained commitment, should reap the rewards in the next five to six years.
The report comes from six different major organisations, including the Malaria Vaccine Initiative and Medicines for Malaria Venture. Speaking to Professor Awa Marie Coll-Seck, executive director of the Roll Back Malaria partnership, which co-ordinates the global effort, I was keen to know whether this means that the mosquito-borne disease that kills 750,000 a year – mostly small children – in developing countries is on the way out.
In the last few years, she said, the roll-out of bed nets to protect against mosquito bites at night, indoor spraying with insecticide, and better access to good treatment has enabled 40 countries to cut malaria deaths and cases by 50%. “This has put it in the minds of all people that it is possible to defeat this disease and have, one day, a malaria-free world,” she said.
Some countries have eliminated malaria completely – such as Morocco in the last two years. Others are making impressive progress, such as South Africa and Swaziland, where cases have dropped by 90%. This is the way it has to happen, with one region or country after another eliminating the disease. It will take time. “We will one day go towards eradication, but it is not now,” said Coll-Seck. “We are not saying tomorrow we will eradicate malaria. We have a long way to go. We need new tools and the financing of malaria must be sustained.”
Of course, the only disease the world has managed to eradicate is smallpox and that was thanks to a vaccine. Polio is forever tantalisingly close and never quite there, because not only a vaccine is needed but the capacity and will and money to reach all children with the vaccine. Huge efforts continue to be made in the remaining pockets – I saw the impressive mobilisation myself in India a year and a half ago(this is the piece I wrote). But even where eradication is elusive, vaccines can drastically cut the death toll of infectious diseases.
So one of the tools Coll-Seck mentions is indeed a vaccine. One of the big surges in malaria research funding has been for the development of GlaxoSmithKline‘s RTS,S vaccine, which is now in final trials in Africa and may give children 50% to 60% protection, we hope. Between 2004 and 2009, says the report, 28% of malaria research funding has gone into vaccines, with 38% into drugs, 23% to basic research but only 4% into vector control products – essentially new insecticides to replace the cheap but controversial DDT, which causes environmental damage if used outside – and 1% into new diagnostics. That reflects “donor funding preferences”, the report says. The two latter areas badly need more money, says Coll-Seck.
Once again, it is the Bill and Melinda Gates Foundation that has led from the wallet. Two organisations – the foundation and the US National Institutes of Health – “provided a striking half of global malaria R&D funding in 2007-09, and were responsible for 85% of the global increase in malaria funding”, says the report.
So what are the hurdles ahead, I asked Coll-Seck. Sustained finance is still the number one priority, she says. Funding overall for malaria (not just research) plateaued in 2010. Some 70% of it comes through the the Global Fund to Fight Aids, Tuberculosis and Malaria, which is struggling to keep donations up. The second issue is resistance to the only drug that works well – artemisinin – which has been found on the Thai/Cambodia border, underlining the need for new drugs and the importance of using those we have properly. And the third, she says, is maintaining a strong and well co-ordinated partnership between all the countries and organisations involved in the fight against malaria.
So there is much more to do and much further to go, and eradication may be no more than a distant dream – but heartening to see such progress.
Malaria Fight Hits Snag
Amos Nyambane | 29 Jun 2011
AllAfrica.comAn NGO yesterday said mosquito nets are being misused in Kisii and Nyamira counties. The organisation said this is hampering the campaign against malaria in the areas. “The misuse of mosquito nets is greatly affecting the malaria campaigns in the regions. People must understand that they are issued with the nets to protect themselves from the disease not as chicken cages or garden fences,” said Douglas Mobasi, Perlin Project manager.
Mobasi said the predominance rate of malaria in the region declined with 86 percent of children below five years and 73 percent of pregnant women sleeping under the nets in that order. Addressing a one day stakeholder’s workshop at Dado Hotel in Kisii, the manager challenged the locals having the nets to use them for the prevention of malaria.
The name of his company, 141 Repellent, is based on a business model that means just that: one for one. For every bottle the company sells, it will donate one malaria treatment for a bed net in the developing world.” http://www.kdvr.com/health/la-he-summer-health-natural-repellent20110601,0,4142738.story
The human and economic cost of malaria in Nigeria is staggering. There are currently 110 million clinically diagnosed cases in a population of 151 million. Malaria kills 250,000 children under five years old in Nigeria every year, and is the cause of 11% of maternal deaths. 60% of out-patient visits and 30% of hospitalizations in the country are malaria-related.
In addition to the enormous toll malaria takes on public health, it is also expensive. 132 billion Naira (USD $870 million) is lost every year in the form of malaria prevention and treatment costs and from the loss of overall economic productivity. And yet in spite of the risk malaria poses to the Nigerian people, health surveys from 2006 to 2008 indicated that only 8% of households in the country owned at least one insecticide-treated net (So-called ITNs).
Needless to say, there is an urgent need for ramped-up malaria prevention efforts in Nigeria. The Nigerian government has been collaborating with a variety of international organizations, including the World Bank, World Health Organization, UNDP and UNICEF on a campaign to “Roll Back Malaria.” This effort has led to the creation of the National Malaria Control Program (NMCP) that seeks to unify all of the disparate pieces of the Nigerian malaria control strategy at the national, regional and local levels.
A quasi-instantaneous data collection system allows for more rapid response and more immediate distribution of food and other aid. The availability of timely and accurate information dramatically increases UNICEF’s ability to identify and resolve problems as they arise and translates into a more efficient and rational allocation of resources. RapidSMS is more than just a data collection tool, however. Erica Kochi, a communications specialist on the UNICEF Innovation team, says it’s a “two-way system.” RapidSMS allows for an end user (most likely a field monitor) to report data. But there is also a “pull aspect,” Kochi explains, so a field worker can quickly access important information from a central, web-hosted database.
UNICEF first deployed RapidSMS in Nigeria in mid-2009 to track and collect data from the Immunization Plus days, a polio eradication initiative of the National Primary Healthcare Development Agency. In order for RapidSMS to be used in the first phase of the bednet distribution program, new features had to be created, says Akinbo, UNICEF’s local software developer. Because it was designed with flexibility and scalability in mind, RapidSMS is relatively easy to customize for specific projects with technical expertise.