Long-Lasting Insecticidal Nets (LLINs) have a substantial effect on mosquitoes, even if the contact is brief, according to a fascinating new study of mosquito behaviour carried out at Liverpool School of Tropical Medicine.
The study set out to investigate how mosquitoes interact with bednets, now widely regarded as the most effective preventive element in malaria control.
Using infra red technology it tracked the flight of Anopheles Gambiae mosquitoes around bednets that were occupied by people. Four key behaviours were identified: swooping, visiting, bouncing and resting. Nearly 75% of the activity took place at the top of the bednet above the occupant’s torso.
Bednets that were treated with insecticides had a rapid effect on mosquitoes—contact of even less than a minute substantially reduced activity. After 30 minutes there was virtually no activity around the insecticide treated bednets. The researchers concluded that LLINs do not repel mosquitoes, but they function as a ‘highly efficient fast-acting baited insecticide trap.’
The paper ‘Infrared video tracking of Anopheles gambiae at insecticide-treated bed nets reveals rapid decisive impact after brief localised net contact’ is published in Scientific Reports. You can read it online here.
Parker, J.E.A. et al. Infrared video tracking of Anopheles gambiae at insecticide-treated bed nets reveals rapid decisive impact after brief localised net contact. Sci. Rep. 5, 13392; doi: 10.1038/srep13392 (2015)Scientistsare the Unsung Heroes of Our Age 27th October 2015
It’s not often that we think of scientists as heroes. More often than not they are portrayed as being a bit geeky, possibly dangerous. But last year, I began to see them in a different light.
I was in a meeting of scientists, quite a few of them chemists. One of our industrial partners was explaining how they were getting on with the search for a new chemical compound to kill mosquitoes.
Frankly, I didn’t understand most of the discussion because it was highly technical, but I saw a picture emerging of the amazing battle that these scientists were engaged in every day.
To my highly untrained unscientific mind it sounded like this (please forgive me scientists everywhere, I’m a journalist):
‘We tried to add a blob onto the left quadrant of the compound but that didn’t work so we wrestled a grommet from another compound, and looked at how other scientists had tackled the problem in a completely different area. We lassooed some wild elements and added them to the mix, herding a whole tribe of unique components into the circle. And this strange compound seems to work.’
I know that sounds crazy, but that’s what it sounded like. What touched me was the sense of a battle. These scientists, as it were, struggling to defeat a powerful enemy that was fighting back in every direction.
That’s where the idea of Heroic Chemistry came from. It grew when I visited Burkina Faso and saw the work local scientists are doing at our field trial sites. Not only are they testing the new compounds to see if they work where it matters, where malaria is endemic, but they’re also testing to see if local insecticide-resistant mosquitoes are affected by the new compounds. And African scientists, who live with the problem on their doorstep, are also beginning to see new patterns of mosquito behaviour and think about completely new solutions. These are people who’ve suffered from malaria every year of their lives so they know the battleground well.
It’s all very exciting. We are not too far away from having several new designed-from-scratch insecticides available to fight malaria. According to a group of leading academics (Bhatt et al, Nature.com 2015) insecticide treated bed nets and indoor residual spraying with insecticides are responsible for the biggest part of the gains in the battle against malaria over the past 15 years. Nearly 78% of the cases averted are due to vector control, which means about 500 million people protected from malaria.
That’s why the work these scientists are doing is heroic. It really does have the potential to change the world as we know it. Millions of liveswill continue to be saved, millions of children will grow up into healthy productive lives, some of the poorest countries in the world will reap the economic benefits of a healthy population.
That’s why I wanted to make this film. To say thank you to the scientists who, behind the scenes, make it all happen. You’re my heroes.Don’t Take Our Word for It—Vector Control Saves Lives 18th April 2016
Malaria rates halved throughout sub-Saharan Africa in the years between 2000 and 2015 as a consequence of greatly improved malaria interventions.
These impressive gains reflect a change of emphasis to make vector control a priority in malaria control programmes. Widespread distribution of insecticide-treated bednets made the biggest contribution, together with indoor residual spraying with insecticides through a coordinated control programme in 15 malaria endemic countries. Together these vector control interventions accounted for 78% of the gains.
Globally renowned researchers from leading institutions across the world compiled the figures using a data-driven approach informed by empirical observation in the field. Their conclusions emphasise the key role vector control plays in saving lives and pushing back malaria. They are also a reminder that there is still a long way to go, and the gains need to be maintained: vector-borne diseases like malaria can rebound easily, as past experience has shown.
Maintaining progress is no easy task, faced with increasing insecticide resistance in Africa. Fortunately, after 10 years of successful development with our industrial partners, new insecticide formulations are already in action and proving effective where there is resistance, anti-resistance bednets are on the near horizon, and several novel public health insecticides for bednets and indoor residual spraying are well on the way, to provide the next generation of vector control tools. But a proactive approach to their use will be essential to prevent future resistance from developing.
Malaria still kills over 433 thousand people a year, mostly children and pregnant mothers; reason enough not to take the pressure off, and to apply all available measures to protect vulnerable people and communities from this ancient scourge. It will need a toolbox of insecticides, drugs, vaccines and diagnostics working together to bring about a permanent solution. Each has a vital role to play, with vector control continuing to be a key element in bringing this vector-borne disease to an end.
This authoritative report* highlights the vital role of vector control in saving lives from malaria, now and in the future. It is worth taking time to consider its analysis. Don’t take our word for it, read the facts for yourself and draw your own conclusions.
*The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015. S Bhatt, et al.
Nature 526, 207–211 08 October 2015)
Read the Full Report here
Read a review of the Report hereThe Menace of Zika 15th February 2016
Zika virus is the latest vector borne disease to hit the headlines. It is primarily transmitted by infected mosquitos, but one of the reasons it’s been in the headlines is that it can also be transmitted by sexual contact.
There’s also great concern because of the links to Zika virus and microcephaly, a medical condition in which a baby is born with an abnormally small head, which can lead mental and other complications. Menacing, especially as you can have the virus without being aware of it.
The jury is still out on the specifics of how the virus is spread but there is clear evidence that the main culprit is the mosquito — in this case the species Aedes aegypti, which is also responsible for transmitting yellow fever, dengue fever and chikungunya. It’s reported that the mosquito can bite four or five people in the course of one blood meal, meaning that it can be spread very rapidly. The virus has already been reported in many Latin American and Caribbean countries and some reports suggest as many as 1.5 million people may now be affected.
So Zika virus joins malaria as a threatening mosquito-transmitted disease. There is all manner of crazy speculation around as to how the disease has become so prevalent — it was first identified in Uganda as long ago as 1947. As you would expect with a story that has all the potential elements of media hype, there’s a lot of ‘quackery’ (as one eminent entomologist described it) flying around about about the origins of the current outbreak. So far there is no scientific basis for any of this, but the speculation prompted the WHO to state categorically that there is no evidence linking Zika to genetically modified mosquitos.
So what do we know? To save me repeating what has already been written, consult the briefing paper below:
Zika Virus, Vector Control and IVCC.
Mosquito Resistance a Growing Concern, says WHO 23rd November 2016
WHO reports 60 countries have recorded mosquito resistance to at least one of the four insecticides used in long-lasting insecticide treated nets (LLINS) and indoor residual spraying (IRS) since 2010. Of these, 49 countries have reported resistance to two or more insecticide classes. WHO says that if resistance continues to intensify, the mosquito-killing capacity of LLINs and indoor residual spraying may steadily weaken.
This would be a tragedy for sub-Saharan Africa where acclaimed research last year demonstrated that LLINs accounted for about 78% of the substantial malaria gains over the past 15 years or so. (Read more about this here.)
If the battle against malaria is to continue to drive back this scourge from sub-Saharan Africa, the need to continue to develop new public health insecticides is paramount. Fortunately, due to the foresight of leading vector science academics who saw the potential threat over 15 years ago, the Bill & Melinda Gates Foundation and other forward thinking funders have invested appropriately in the search for new public health insecticides. IVCC was established in 2005 as the only vector control focused Product Development Partnership (PDP) and has worked closely with world-leading vector scientists and agro-chemical companies to design and develop novel public health insecticides targetted precisely at killing the mosquitoes that transmit malaria.
Professor Hilary Ranson, one of the world’s leading authorities on insecticide resistance, warned earlier this year that pyrethroid resistance is the biggest biological threat to malaria control in Africa. (Read about this here.) Together with other leading specialists in this area she says that the urgent need for new vector control products is apparent, and the new vector control products that are in the pipeline must be rationally deployed in order to slow down future resistance developing.
IVCC has a healthy pipeline of novel vector control tools, itself a product of consistent commitment by public health funders and industrial partners to finding a solution to the global threat of insect-transmitted diseases.
*The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015. S Bhatt, et al.