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Malaria vaccines
Topic Started: 16 Feb 2017, 01:43 AM (107 Views)
skibboy
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15 February 2017

Bite-mimicking malaria vaccine shows promise: study

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© USDA/AFP/File / by Mariëtte Le Roux | According to the World Health Organization, there were 212 million malaria cases in the world in 2015 and 429,000 deaths

PARIS (AFP) - A malaria vaccine that mimics being bitten by an infected mosquito provided up to 100 percent protection for ten weeks in a human drug trial, its makers said Wednesday.

A newer version of the PfSPZ vaccine required fewer shots and a lower dose of live malaria parasites than previously tested, they reported in the journal Nature.

"We are extremely encouraged by these findings," said Stephen Hoffman of vaccine developer Sanaria, a company based in Maryland.

But he stressed a lot of work lay ahead, and a registered vaccine may take another two years to reach the market.

The experimental vaccine, called PfSPZ-CVac, uses a live, immature form of the malaria parasite, called a sporozoite, to stimulate an immune reaction in humans.

In a previous version of the vaccine, sporozoites were exposed to radiation to weaken them before they were injected into the bloodstream.

In that experiment, reported in 2013, trial subjects were given five shots, each with 135,000 sporozoites, or three doses with up to 1.8 million sporozoites in total.

The highest dose provided 100 percent immunity to six volunteers.

For the latest trial, volunteers received only three injections over eight weeks or 10 days at a German lab, with sporozoite doses ranging from 3,200 to 51,200 per shot.

All nine volunteers in the high-dose group enjoyed malaria protection 10 weeks after the last dose, compared to six out of nine in the medium- and three out of nine in the low-dose groups.

- No radiation -

"The ability to complete an immunisation regime in 10 days will facilitate the use of PfSPZ-CVac in mass vaccination programmes to eliminate the malaria parasite and to prevent malaria in travellers," Hoffman said in a statement.

The reason that fewer sporozoites were required this time, was that they were not irradiated before injection, he explained.

Instead, the vaccine was administered in conjunction with an anti-malarial drug, chloroquine, to stop the parasites causing disease once in the human body.

The candidate vaccine is being developed against the Plasmodium falciparum mosquito-borne parasite, by far the deadliest type.

Further trials are to follow in Mali, Ghana, the United States and Gabon.

According to the World Health Organization, there were 212 million malaria cases in the world in 2015 and 429,000 deaths.

More than 90 percent of deaths occur in Africa.

Another vaccine candidate called RTS,S, developed by GlaxoSmithKline, is being tested in children -- the most affected population.

It is considered the most advanced candidate, but results last year from a Kenyan trial showed it was only about four percent effective after seven years.

The developers of PfSPZ are aiming for efficiency of about 80-90 percent protection lasting six months to a year, Hoffman said.

This would make it ideal for people travelling to malaria areas.

"We hope we'll be there this year, maybe next year. We're closing in on it," he told AFP.

by Mariëtte Le Roux

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skibboy
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22 February 2017

First drug-resistant malaria parasite detected in Africa

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© SANARIA INC/AFP/File | Africa now joins southeast Asia in hosting a malaria parasite that is partially resistant to the top anti-malaria drug, artemisinin

MIAMI (AFP) - For the first time in Africa, researchers said Wednesday they have detected a malaria parasite that is partially resistant to the top anti-malaria drug, artemisinin, raising concern about efforts to fight a disease that sickens hundreds of millions of people each year.

The discovery means that Africa now joins southeast Asia in hosting such drug-resistant forms of the mosquito-borne disease.

Malaria infected more than 200 million people and killed some 438,000 people worldwide in 2015, most of them children in Africa.

"The spread of artemisinin resistance in Africa would be a major setback in the fight against malaria, as ACT (artemisinin-based combination therapy) is the only effective and widely used antimalarial treatment at the moment," said lead author Arnab Pain, professor at the King Abdullah University of Science and Technology.

"Therefore, it is very important to regularly monitor artemisinin resistance worldwide."

The drug-resistant malaria parasites were detected in a Chinese patient who had traveled from Equatorial Guinea to China, said the report led by Jun Cao from the Jiangsu Institute for Parasitic Diseases in China.

The study was published in the New England Journal of Medicine.

Combination therapy with artemisinin usually clears malaria from the blood in three days.

In southeast Asia, strains of the malaria-causing agent, Plasmodium falciparum, have grown relatively tolerant to artemisinin, in what is known as "partial resistance."

Most patients can still be cured, but it takes longer.

World Health Organization experts are concerned that P. falciparum could eventually become completely resistant to artemisinin, just as it has to other antimalarial drugs.

Researchers said they found the parasite carried a new mutation in a gene called Kelch13 (K13), which is the main driver for artemisinin resistance in Asia.

They then confirmed the origin of the resistance was Africa, by using "whole-genome sequencing and bioinformatics tools we had previously developed -- like detectives trying to link the culprit parasite to the crime scene," he said.

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skibboy
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Malaria: Kenya, Ghana and Malawi get first vaccine

By James Gallagher
Health and science reporter, BBC News website

24 April 2017

Posted Image
The vaccine has been tested extensively in more than 15,000 children

The world's first vaccine against malaria will be introduced in three countries - Ghana, Kenya and Malawi - starting in 2018.

The RTS,S vaccine trains the immune system to attack the malaria parasite, which is spread by mosquito bites.

The World Health Organization (WHO) said the jab had the potential to save tens of thousands of lives.

But it is not yet clear if it will be feasible to use in the poorest parts of the world.

The vaccine needs to be given four times - once a month for three months and then a fourth dose 18 months later.

This has been achieved in tightly controlled and well-funded clinical trials, but it is not yet clear if it can be done in the "real-world" where access to health care is limited.

It is why the WHO is running pilots in three countries to see if a full malaria vaccine programme could be started.

It will also continue to assess the safety and effectiveness of the vaccination.

Dr Matshidiso Moeti, the WHO regional director for Africa, said: "The prospect of a malaria vaccine is great news.

"Information gathered in the pilot programme will help us make decisions on the wider use of this vaccine.

"Combined with existing malaria interventions, such a vaccine would have the potential to save tens of thousands of lives in Africa."

The pilot will involve more than 750,000 children aged between five and 17 months.

Around half will get the vaccine in order to compare the jab's real-world effectiveness.

In this age group, the four doses have been shown to prevent nearly four in ten cases of malaria.

This is much lower than approved vaccines for other conditions.

It also cuts the most severe cases by a third and reduces the number of children needing hospital treatment or blood transfusions.

But the benefits fall off significantly without the crucial fourth dose.

Ghana, Kenya and Malawi were chosen because they already run large programmes to tackle malaria, including the use of bed nets, yet still have high numbers of cases.

Each country will decide how to run the vaccination pilots, but high-risk areas are likely to be prioritised.

Despite huge progress, there are still 212 million new cases of malaria each year and 429,000 deaths.

Africa is the hardest hit and most of the deaths are in children.

The pilots are being funded by: Gavi, the Vaccine Alliance, the Global Fund to Fight Aids, Tuberculosis and Malaria, Unitaid, the WHO and GSK.

Dr Seth Berkley, the chief executive of Gavi, said: "The world's first malaria vaccine is a real achievement that has been 30 years in the making.

"Today's announcement marks an important step towards potentially making it available on a global scale.

"Malaria places a terrible burden on many of the world's poorest countries, claiming thousands of lives and holding back economies.

"These pilots are crucial to determining the impact this vaccine could have on reducing this toll."

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skibboy
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15 June 2017

Warmer climate threatens malaria spread in Ethiopia: study

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© AFP/File | According to the World Health Organization, there were 212 million cases of malaria worldwide in 2015, and 429,000 deaths

PARIS (AFP) - Cool, high-lying areas of Ethiopia hitherto shielded from heat-loving malaria mosquitoes are increasingly exposed to the disease as the climate warms, researchers said Thursday.

Most Ethiopians live in the country's highlands, and have long enjoyed natural protection against mosquitoes carrying the malaria-causing parasites Plasmodium falciparum and P. vivax.

But the buffered area has been shrinking since 1981, scientists reported in the journal Environmental Research Letters.

About six million people live in the newly-vulnerable regions.

Air temperatures below 18 degrees Celsius (64.4 degrees Fahrenheit) prevent development of P. falciparum.

The survival threshold for P. vivax is 15 C, according to the research team.

Low temperatures also impede the spread of mosquitos that host the parasites.

Since temperatures decrease with altitude, much of the Ethiopian highlands -- 1,500 to 2,500 metres (4,921 to 8,202 feet) above sea level -- were beyond the reach of malaria transmission.

To date, it was not known whether the mercury had risen in the East African highlands, or whether global warming contributed to a recent upsurge in malaria in the region.

To find out, a team from the University of Maine and Columbia University in New York compiled a national temperature dataset for Ethiopia covering the period 1981-2014.

They discovered that temperatures rose at least 0.22 C (0.4 F) per decade.

The team then used the new climate data to pinpoint the highest elevation where the average minimum temperature never exceeds the 18 C or 15 C malaria threshold.

"The elevation at which the temperature thresholds are met has risen by more than 100 metres (328 feet) since 1981," the study's lead author Bradfield Lyon of the University of Maine, said in a statement.

Taking into account natural variability in the regional climate and impacts of the seasonal El Nino weather phenomenon, the observed rise was "consistent" with global warming caused by mankind's burning of fossil fuels, the authors found.

"Of particular concern is that the... changes are occurring in the densely populated highlands, where higher elevation has historically served as a buffer against malaria transmission," they wrote.

According to the World Health Organization, there were 212 million cases of malaria worldwide in 2015, and 429,000 deaths.

Ninety percent of malaria cases and deaths occur in Africa.

Children under five are most at risk.

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skibboy
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Extreme gardening to help tackle malaria

By Michelle Roberts
Health editor, BBC News online

5 July 2017

Posted Image
The Prosopis juliflora shrub occupies millions of hectares of Africa

Gardening could be a powerful weapon against malaria, culling mosquito populations by cutting off their food supply, say researchers.

A team tested their idea in nine villages in the arid Bandiagara district of Mali, West Africa.

Removing flowers from a common shrub appeared to kill off lots of the older, adult, female, biting insects that transmit malaria.

Without enough nectar the "granny" mosquitoes starve, experts believe.

Killing granny

Getting rid of the mature females can stop the cycle of malaria transmission.

Posted Image
These Anopheles mosquitoes carry the malaria parasite in their salivary glands and pass it on to people when they bite and draw blood

The infected person can then infect other younger, biting, female mosquitoes - which are looking for a rich blood meal as they become fertile and make eggs - because their blood now contains the parasite.

It takes about 10 days for a newly infected young female mosquito to become contagious to humans. That may not sound long, but for an insect, it is.

By the time she can transmit malaria, she's pretty old.

Although she will feed on blood, she also relies on flower nectar for energy to stay alive.

Shrubbery

In the Bandiagara district of Mali, there is one invasive plant that researchers believe is a feeding ground for malaria-transmitting mosquitoes.

The flowering Prosopis juliflora shrub is a bit of a horticultural thug and now occupies millions of hectares of the African continent.

Native to Central and South America, it was introduced into Africa in the late 1970s in an attempt to reverse deforestation and "green up" the desert.

Experts in Mali, along with researchers from the Hebrew University of Hadassah Medical School, Israel, and the University of Miami in the US, set up a horticultural experiment to see if removing the flowers from this plant might help kill off local mosquitoes.

They picked nine villages - six with lots of the flowering shrub and three without.

In three of the six villages, they hacked down the flowers.

They set light traps around all the villages to catch mosquitoes so they could see if the "gardening" had helped cull the insects.

Villages where they removed the flowers saw mosquito numbers collected in the traps fall - the total number of mosquitoes across these villages decreased by nearly 60% after removal of the flowers.

Importantly, the number of old female mosquitoes dropped to similar levels recorded in the three villages without any of the shrubs.

They don't have direct proof, but the researchers believe the mosquitoes died of starvation.

The reported their findings in the journal Malaria Research.

Prof Jo Lines is a malaria control expert from the London School of Hygiene and Tropical Medicine.

He says the novel approach holds amazing potential, alongside other malaria prevention strategies.

"It appears to show that by changing the landscape, not using insecticides or drugs, we can make a difference."

But he said it might not work so well in lush tropical regions where nectar-rich plants are in abundance.

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skibboy
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Rare malaria death of girl in northern Italy puzzles doctors

5 September 2017

Posted Image
The female Anopheles mosquito passes on the malaria parasite by feeding on human blood

A four-year-old Italian girl has died of cerebral malaria in northern Italy, a region free of the disease, in what doctors see as a very mysterious case.

Sofia Zago died in Brescia on Sunday night, after being rushed to hospital with a high fever on Saturday.

Italy is free of the Anopheles mosquito that carries cerebral malaria, the deadliest form of the blood disease.

But after a scorching August, some fear that it might have reached Italy.

A flight could have brought it in.

Sofia had been on holiday with her parents at Bibione, an Adriatic resort near Venice.

Trento, where the girl's malaria was diagnosed on Saturday, lies within the Trentino region in the foothills of the Alps.

"It's the first time in my 30-year career that I've seen a case of malaria originating in Trentino," said Dr Claudio Paternoster, an infectious diseases specialist at Trento's Santa Chiara Hospital.

Since the 1950s, Italy has not had a malaria problem because mosquito-infested marshes were drained.

There is speculation that Sofia might have caught malaria from one of two children treated for it at the Trento hospital after 15 August.

They had caught it in Africa, and recovered.

Sofia had had treatment there for child diabetes and there was a break before her emergency readmission to the hospital at the weekend.

A Trentino health official, Paolo Bordon, said Sofia had not been in the same ward as the other two children.

Sofia had not had a blood transfusion, he added, stressing that the treatments for malaria and diabetes were utterly different.

The Plasmodium Falciparum parasite carried by the Anopheles mosquito can kill a human within 24 hours.

About 438,000 people died of malaria in 2015 in the 95 tropical countries where it is endemic, Italy's Corriere della Sera daily reports.

____________________________________________________________________________________________________________________________________________


Rare case for Europe

By Michelle Roberts, Health Editor, BBC News Online

Only some types of mosquito are able to transmit the disease from person to person.

Risky insects are found in large areas of Central and South America, Africa, Asia, the South Pacific and some parts of Eastern Europe, but not in the rest of Europe.

As a result, malaria is largely limited to tropical areas - cases appearing within the European Union are typically "suitcase" ones, linked to recent travel to other parts of the world where malaria is present.

The latest case in northern Italy has baffled experts.

It is not clear how the girl caught it, but her case is not unique.

The European Centre for Disease Prevention Control closely monitors cases and has found a few cases of "locally acquired" malaria in the EU - two in France and three in Spain in 2014.

But there were explanations for how some of these might have occurred.

One was a patient who had received a kidney from a donor with malaria; another was a newborn whose mother had recently returned from Equatorial Guinea.

One of the Spanish patients had no history of travel, but lived a few kilometres from a town where a "suitcase" malaria person lived.

No infected local mosquitoes were found, but lab tests showed two people had an identical strain of the disease.

____________________________________________________________________________________________________________________________________________


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skibboy
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Malaria breath test shows promise

By Michelle Roberts
Health editor, BBC News online

7 November 2017

Posted Image

People with malaria give off a distinctive "breath-print" that could be used as a test for the disease, according to American scientists.

They had already tried out a crude prototype breathalyser in Africa, a tropical medicine conference heard.

The test was reasonably good at detecting cases in children, but needs developing to become a routine device.

One of the odours it sniffs out is identical to a natural smell that attracts insects that spread malaria.

Pine trees and conifers emit these terpenes to summon mosquitoes and other pollinating insects, say the researchers, from Washington University in St Louis.

Posted Image

They believe people with malaria who have this odour in their breath may also attract mosquitoes and infect more of the biting insects, which can then spread the disease to other people that they bite.

Although the test needs perfecting, it could offer a new cheap and easy way to help diagnose malaria, Prof Audrey Odom John and colleagues say.

Distinct odour

The prototype breath test detects six different odours or volatile organic compounds to spot cases of malaria.

The researchers tried it on breath samples from 35 feverish children in Malawi, some with and some without malaria.

It gave an accurate result in 29 of the children, meaning it had a success rate of 83%.

This is still too low for the test to be used routinely, but the researchers hope they can improve its reliability and develop it into an off-the-shelf product.

Simple, rapid blood tests for malaria are already available, but they have limits, say the Washington University researchers.

Testing blood can be expensive and technically challenging in rural settings.

A non-invasive method of detection that does not require blood samples or technical expertise could be of great benefit.

Prof James Logan from the London School of Hygiene and Tropical Medicine said: "The rapid detection of asymptomatic malaria is a challenge for malaria control and will be essential as we move towards achieving the goal of malaria elimination. A new diagnostic tool, based on the detection of volatiles associated with malaria infection is exciting."

He said more work was now needed to see if it could be made into a reliable test.

The findings are being presented at this year's annual meeting of the American Society of Tropical Medicine and Hygiene.

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