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Malaria: The Disease & Countermeasures Against It

Rrose_Selavy

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Following on from an earlier thread about Mosquitoes ...

Scientists create GM mosquitoes to fight malaria and save thousands of lives
· Plan to breed and sterilise millions of male insects
· Leader says project almost ready for testing in wild

David Adam, environment correspondent
Monday October 10, 2005

Guardian

Genetically modified mosquitoes could soon be released into the wild in an attempt to combat malaria. Scientists at Imperial College London, who created the GM insects, say they could wipe out natural mosquito populations and save thousands of lives in malaria-stricken regions.
Led by Andrea Crisanti, the team added a gene that makes the testicles of the male mosquitoes fluorescent, allowing the scientists to distinguish and easily separate them from females. The plan is to breed, sterilise and release millions of these male insects so they mate with wild females but produce no offspring, eradicating insects in the target region within weeks.

Professor Crisanti said: "Our mosquitoes are nearly ready for testing in the wild. This is a technology that works and could make a real difference. The beauty is that it's very specific. Unlike insecticides, sterile males target only the species you want to attack."

Mosquitoes that spread malaria have long been a target for sterile male technology, which has been used to eradicate the screwworm fly from the US, Mexico and Central America.

The International Atomic Energy Agency has been using its radiation technology to support health projects, and wants to release sterile mosquitoes to tackle malaria in northern Sudan and on Reunion island in the Indian ocean - but they and other groups have been hampered by an inability to distinguish the males, which do not bite people. Female mosquitoes transmit malaria, even if sterile, so releasing them alongside males would make the situation worse.

Prof Crisanti said: "The really challenging problem is to identify the males. There is no difference between the larvae and as adults they fly, so the logistics of trying to separate them when they're adults is immense."

To solve the problem, his team altered the DNA of the mosquito species Anopheles stephensi, the principal carrier of malaria in Asia, so that the males expressed a fluorescent green protein in their sperm. A sorting machine based on laser light separated male from female larvae, according to whether they glowed or not. Writing in Nature Biotechnology today, the scientists say the machine could sort 180,000 larvae in 10 hours.

The next step is to scale up the technique to provide the millions of GM insects needed to make a large-scale release effective. The scientists also need to check the sterile males will be strong enough to compete with wild rivals when released - the strategy depends on female mosquitoes, who only mate once in their two-week lifespan, choosing sterile males.

Prof Crisanti said other mosquito species could be modified in the same way, including Anopheles gambiae, which is responsible for a large part of the 2.7m deaths caused by malaria each year. He is talking to international agencies about setting up a trial. Scientists have previously considered releasing both male and female mosquitoes that have been genetically modified in a different way, making them unable to transmit malaria. The idea is that altered insects would spread the disruptive genes through natural mosquito populations, but concerns about whether the inserted genes could transfer to other organisms have so far scuppered plans to set up large-scale breeding colonies to test it.

Prof Crisanti argued that, because the new GM mosquitoes are sterilised, releasing them into the environment does not pose significant risks: "It won't transmit any genes to the environment. This allows us to test the transgenic technology in a very safe way that overcomes the previous environmental and safety concerns." Releasing males only would ensure people were not bitten by GM mosquitoes, he added.

Sue Mayer of Genewatch agreed that the new GM insect did address some of the previous concerns, but she called for thorough testing of the mosquitoes before they were considered for release. "Changing one gene can sometimes affect others, so there are still questions to ask," she said.

There are political barriers too. The London group's insect is best suited to tackling malaria in impoverished urban areas of south-east Asia and India, where World Health Organisation trials of sterile male mosquitoes to fight dengue fever collapsed in the 1970s amid biowarfare accusations. The males of the mosquito involved in the Delhi trials could be separated because their pupae were smaller, but they were never released after newspaper articles claimed the experiment might secretly be used to gather data on how to spread yellow fever.

Chris Curtis, a malaria expert with the London School of Hygiene and Tropical Medicine who worked on the WHO project in India, said: "We were all set to go and there was a huge uproar. You have to handle the public relations very carefully."

Female mosquitoes can travel several kilometres after mating, he said, so the sterile male technique is best suited to isolated insect populations, such as in cities. "If females that have already mated fly in from outside your release area then they carry on laying fertile eggs. That's fatal."

Footnotes

Malaria

The world's most common and deadly parasitic disease. It is spread from person to person when female mosquitoes feed on human blood. Infects up to 500 million people each year, and kills an estimated 2.7 million people.

Sterile male technology

Male insects can be sterilised using chemicals and radiation. If enough sterile males can be released to breed with females, the insect population of a target region can crash within weeks.

Fluorescent green protein

Originally identified in jellyfish that live in the cold waters of the north Pacific ocean. The protein glows green under ultraviolet light.

Large-scale release

Huge numbers of sterile males would have to be released, possibly several hundred thousand at different locations throughout a city in several waves over a month.

Yellow fever

The disease was absent from Asia but appeared on a US list of potential biowarfare agents. When an Indian journalist discovered the common name of the insect involved was "yellow fever mosquito" the trials were halted.

Guardian Unlimited © Guardian Newspapers Limited 2005
 
Africa@home

Coming down to Earth

Jul 13th 2006
From The Economist print edition


Linking up computers to defeat malaria

IF MANKIND ever makes the acquaintance of an extraterrestrial alien, the chances are that first contact will come through a humble desktop computer. The SETI@home project, which searches for signs of intelligent broadcasting among the natural radio signals coming from the sky, depends for its computing power on the spare capacity of a zillion small, private machines around the world.

Although SETI@home may or may not find what it is looking for, it has unarguably started a fashion. Donating spare computer cycles to worthy causes is a cheap way of helping those who cannot afford huge piles of hardware to achieve their goals. The latest organisation to take advantage of this is one of the most worthy of all. Africa@home aims to use that spare capacity for no less a task than the defeat of malaria, a disease that kills more than 1m people a year.

Africa@home is a collaboration between the Swiss Tropical Institute, CERN (a big particle-physics laboratory also based in Switzerland) and a group of universities, including three from Africa. Its aim is to develop a long-term model of malaria epidemiology, which it can use to test different ways of combating the disease.

The institute already uses models to study the short-term dynamics of malaria transmission. However, the computing power needed to generate accurate long-term results is beyond its means. Which is where CERN comes in. Besides studying the fundamental nature of reality, the laboratory is also a huge computing centre. Indeed, it is where the world wide web was invented. And, in the wake of the web's success, it has maintained an interest in how to link up lots of small computers so that they can perform tasks beyond most large ones. Long-term epidemiology is an excellent example of such a task.

Using CERN's tools, the universities have devised a program called MalariaControl.net, which takes the institute's model and converts it into a form that can be scattered meaningfully across hundreds—or even thousands—of computers. MalariaControl.net can handle a lot of different sorts of variable, from the changing density of parasites within a human host as an infection progresses to the sort of treatment available in different places around the continent. It also looks at the relationship between parasite density in people and the rate at which humans transfer those parasites back to the mosquitoes that carry them. It can even take account of the time of year, and thus the amount of standing water around for mosquitoes to breed in. Using these variables, it can then predict the result of deploying various drugs, the likely success of methods such as insecticide-covered bed nets that are used to block transmission of the disease, and the probable impact of a vaccine, if and when one becomes available.

A test run using 500 computers has just been completed successfully and the project is now being opened to 1,000 more volunteers (the Africa@home website is accepting registrations). Those volunteers will be able to bask in the knowledge that they are helping to create a cheaper and longer-lasting way of dealing with one of the world's biggest killers. That should be some compensation for not being the first to contact little green men.

http://africa-at-home.web.cern.ch/afric ... /index.htm

http://www.economist.com/science/displa ... id=7159442
 
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This could be very big - and very welcome - news. Full details are provided in the lengthy linked article.
Malaria 'completely stopped' by microbe

Scientists have discovered a microbe that completely protects mosquitoes from being infected with malaria.

The team in Kenya and the UK say the finding has "enormous potential" to control the disease.

Malaria is spread by the bite of infected mosquitoes, so protecting them could in turn protect people.

The researchers are now investigating whether they can release infected mosquitoes into the wild, or use spores to suppress the disease. ...

FULL STORY: https://www.bbc.co.uk/news/health-52530828
 
That would make a huge difference! fingers being crossed here...
 
Worrying news.

A drug-resistant strain of the parasite that causes malaria has been identified by scientists in Rwanda.

The study, published in Nature, found the parasites were able to resist treatment by artemisinin - a frontline drug in the fight against the disease.

This is the first time scientists have observed the resistance to the drug artemisinin in Africa.

The researchers warns that this "would pose a major public health threat" in the continent.

https://www.bbc.com/news/world-africa-53676702
 
Oh, great ... :doh:
Rug rats and yard apes can also serve as malaria moles - unsuspected asymptomatic malaria superspreaders.
Children can be stealth superspreaders of malaria to mosquitoes

Children infected with malaria can become "superspreaders" and pass the parasite to droves of local mosquitoes, even if the kids never develop symptoms of the disease, a new study suggests.

Since this disease is passed from humans to mosquitoes and then back again, rather than from person to person, this finding is worrisome.

If malaria goes untreated in these asymptomatic children, the parasites will continue to circulate among mosquitoes, even in places that employ intensive malaria controls like insecticides, bednets, and free diagnostic tests and treatments. According to new research, presented Wednesday (Nov. 18) at the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH), even a small number of infected children can transmit malaria parasites to a mob of mosquitoes, which can then go on to infect more humans.

From their new research in Uganda, the researchers concluded that asymptomatic children between ages 5 and 15 are the main source of infection for local mosquitoes in the region they studied. Some of these children were so-called superspreaders, meaning they infected a much larger number of mosquitoes than others; in experiments where mosquitoes were fed blood samples from infected people, more than 60% of the resulting mosquito infections could be traced back to just four asymptomatic children, two of whom were school-age. The other two superspreaders were ages 3 and 4. ...

FULL STORY: https://www.livescience.com/asymptomatic-children-malaria-reservoir.html
 
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