Just what the tropical zone needs most

How long before we see it in the Caribbean
February 2011 Last updated at 14:02 ET


New mosquito type raises concern
By Jonathan Amos Science correspondent, BBC News


Close-up image of a mosquito Anopheles gambiae is responsible for the vast majority of malaria cases in Africa


* Malaria vaccine: Inside look at first human trial
* Beating malaria 'impossible' now
* Mosquito ecology 'must advance'

Scientists have identified a new type of mosquito.

It is a subgroup of Anopheles gambiae, the insect species responsible for most of the malaria transmission in Africa.

Researchers tell Science magazine that this new mosquito appears to be very susceptible to the parasite that causes the disease - which raises concern.

The type may have evaded classification until now because it rests away from human dwellings where most scientific collections tend to be made.

Dr Michelle Riehle, from the Pasteur Institute in Paris, France, and colleagues made their discovery in Burkina Faso, where they gathered mosquitoes from ponds and puddles near villages over a period of four years.

When they examined these insects in the lab, they found many to be genetically distinct from any A. gambiae insects previously recorded.

The team grew generations of the unique subtype in the lab to assess their susceptibility to the malaria parasite and this revealed them to be especially vulnerable, more so than indoor-resting insect types.

But Pasteur team-member Dr Ken Vernick cautioned that these mosquitoes' significance for malaria transmission had yet to be established.

"We are in a zone where we need to do some footwork in the field to identify a means to capture the wild adults of the outdoor-resting sub-group," he told BBC News.

"Then we can test them and measure their level of infection with malaria, and then we can put a number on how much - if any - of the actual malaria transmission this outdoor-resting subgroup is responsible for."

The researchers report that the new subgroup could be quite a recent development in mosquito evolution and urge further investigation to understand better the consequences for malaria control.

They also emphasise the need for more diverse collection strategies. The subtype is likely to have been missed, they say, because of the widespread practice of collecting mosquitoes for study inside houses. In one sense this has made sense - after biting, mosquitoes need to rest up and if they do this inside dwellings, the confined area will make them an easier target for trapping. However, the method is also likely to introduce a bias into the populations under study.

Commenting on the study, Dr Gareth Lycett, a malaria researcher from the Liverpool School of Tropical Medicine in the UK, said it was an interesting advance that might have important implications for tackling malaria.
Larvae are collected from natural pools Larvae are collected from pools of water for study

"To control malaria in an area you need to know what mosquitoes are passing on the disease in that district, and to do that you need sampling methods that record all significant disease vectors," he told BBC News.

"You need to determine what they feed on, when and where, and whether they are infectious. And where non-house-resting mosquitoes are contributing to disease transmission, devise effective control methods that will complement bed-net usage and house spraying.

"A recent 12m-euro multinational project (AvecNET), funded by the European Union, and led by the Liverpool School of Tropical Medicine has the specific aims of doing just this."

According to the World Health Organization (WHO), there are more than 200 million cases of malaria worldwide each year, resulting in hundreds of thousands of deaths, most of them in Africa.

Malaria is caused by Plasmodium parasites. The parasites are spread to people through the bites of infected female Anopheles mosquitoes

Have they determined any reason why this type of mosquito is more prone to carry the disease than the other species? I find malaria such a scary virus to contract but you can't really protect yourself 100%. It's pretty much like rolling the dice- it's nearly impossible to protect yourself from all mosquito bites!
Great article!
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park royal cozumel

Messing with genes to wipe out malaria

A team of scientists has developed genetically modified mosquitoes that are unable to transmit malaria.



Malaria, transmitted by mosquito bites, infects an estimated 200 million people per year, with about 1 million people dying as a consequence. (Sang Tan, AP / April 30, 2011)


Booster Shots blog: Recent news from the health world Booster Shots blog: Recent news from the health world
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Armadillos pass leprosy to humans, study finds Armadillos pass leprosy to humans, study finds

New study adds to concerns about animal-to-human resistance to antibiotics

By Amina Khan, Los Angeles Times

April 29, 2011, 8:11 p.m.
Malaria, a parasitic disease transmitted by mosquito bites, has resisted insecticides, mosquito netting and other eradication efforts. Recently, a team of scientists from Imperial College London and the University of Washington in Seattle reported on a genetic approach.

Mosquitoes were inserted with a fungus gene that can attack specific mosquito genes — making it possible, for example, to destroy genes that allow the malaria parasite to reach humans' bloodstreams.

Andrea Crisanti, the paper's senior author and a molecular biologist at Imperial College London, talked about the work, which was recently published in the journal Nature.

Why are you tackling malaria?

Malaria is one of the most important infectious diseases. It infects an estimated 200 million people per year, with about 1 million people dying as a consequence, on the same order as HIV/AIDS and tuberculosis.

If you have enough money, with sustained effort, you can eradicate malaria. In the United States and in Europe, malaria was eradicated. Unfortunately, developing countries don't have the resources to sustain the use of insecticides over long periods of time and different locations. It requires complex logistics, a lot of money, effort and motivation, and a strong political will.

Ideally, it requires a measure that is affordable, easy to implement and sustainable. And such a measure does not exist at the moment.

So we thought if we developed genetically modified mosquitoes that are unable to transmit malaria — and are able themselves to transmit this genetic modification to local mosquitoes, through mating — that would be an effective solution.

How does it work?

So it's a sort of cut-and-paste-function: You have a gene able to attack the other gene, destroy it and copy itself in its location.

The technology is based on a gene that makes an enzyme that selectively recognizes DNA sequences and cuts them. Now if you induce a cut in the DNA, a break in the DNA, you trigger the cell's repair mechanism. The repair mechanism then uses the enzyme's gene as a template to repair the broken DNA sequence. And so, key genes in the mosquito that are involved in malaria transmission can be disrupted. As the mosquitoes breed, it spreads through the population.

In the lab, we saw the mutation spread to more than half the population of mosquitoes we had living in cages. This happened in a time span of 12 to 16 generations of mosquitoes (each generation being between 18 to 30 days in the wild). So it's quite efficient.

What would you target for destruction in the mosquito, and why?

These enzymes can be reprogrammed to attack different DNA sequences, so there is flexibility there. The question is, which sequences do you want to attack?

You could, for example, destroy genes that are important for the parasite. There are some genes that are important for the mosquito to recognize and bite humans rather than animals. Or you could destroy genes that regulate sex development for female mosquitoes, so every generation will produce only males. This will, in the span of a few generations, have tremendous impact on the size of the mosquito population.

Which countries do you want to use this in first?

I don't want to mention any specific countries. I'm thinking sub-Saharan African countries where malaria is highly endemic and they have problems using insecticides or don't have the infrastructure to use them.

India has made fantastic progress in controlling malaria; so has China. They're doing very well now.

How long will it take to significantly reduce malaria?

Without new technology, I would guess we're talking several decades. If our technology works, it can really work in spans of one to two years — once you start to release the modified mosquitoes into the field, they'll do the job in a relatively short time. That's why it's so exciting.

Are people working on other genetic approaches toward controlling malaria?

There's been work done by a group that released genetically modified mosquitoes in the Cayman Islands, but they released sterile male mosquitoes. They're monogamous — so once the male mosquitoes mate, they don't mate again.

The idea is that you make a genetically sterile male, or you introduce genes which kill the females, so in principle, the genes don't spread.

But the technology requires multiple releases, breeding the mosquitoes is not easy, and the technology would be very difficult to implement in Africa. Also, it's been used on a different mosquito that's responsible for the transmission of dengue fever.

Some Good news on dengue

25 August 2011 Last updated at 07:15 ET


Bacteria stops dengue in tracks

By Matt McGrath Science reporter, BBC World Service


Aedes aegyptii The researchers infected the mosquito Aedes aegypti with bacteria


Australian scientists say they have discovered a cheap and effective method of preventing the transmission of dengue fever.

They infected mosquitoes that spread the disease with bacteria that block transmission of the dengue virus.

When the resistant insects were released, they successfully interbred with wild mosquitoes and halted their ability to transmit dengue.

Details of the work are published in the journal Nature.

The researchers are hopeful that this could be a viable control for a disease that affects more than 50 million people worldwide every year.

According to the World Health Organization around one third of the world's population is at risk from dengue fever. The incidence and severity of this untreatable, mosquito-borne illness are increasing in many parts of the world.

Pesticides that kill the specific type of mosquitoes that carry the virus have been the most effective method of control to date, but resistance is rising.

Now a team of Australian scientists say that a simple bacterium called Wolbachia that only infects insects could stop dengue in its tracks.
Natural agent

Professor Scott O'Neill from Monash University, Melbourne, is one of the authors of the research.

"The approach is to use a naturally occurring bacterial agent - An intracellular bacteria that only grows within insects, and it's extremely common in the environment, up to 70% of insects naturally carry it."

After a series of laboratory experiments that proved the power of Wolbachia to restrict the abilities of mosquitoes to transmit dengue, the scientists then released several hundred thousand of them in Queensland in northeastern Australia.

Scott O'Neill explained that a critical aspect was getting the consent of the community to the idea of releasing even more mosquitoes into the environment.

"We spent a considerable amount of time preparing the community before we did the open field tests. A key component was an independent risk analysis undertaken by the CSIRO (Commonwealth Scientific and Industrial Research Organisation - Australia's national science agency). It indicated that over a 30 year time frame any potential for a negative risk with these experiments was considered negligible," he said.

"The mosquitoes were placed in containers, we filled up a van with these containers and drove around early in the morning in the neighbourhood and simply lifted the cover off these containers and the mosquitoes would fly out."

Within months, a wave of infection by the bacterium had spread to almost all the wild mosquitoes rendering them incapable of passing on dengue.

The scientists are uncertain as to why Wolbachia blocks the ability to transmit dengue, but Professor O'Neill said they have two theories: "The first relates to the immune system. The data suggests that the presence of Wolbachia boosts the immune system and helps the mosquito fight off the effects of dengue.

"Other evidence suggests that Wolbachia is competing for key sub-cellular molecules that the virus needs to replicate such as fatty acids - the jury is still out, it might be a combination of both."

The researchers say that further field tests are needed in countries like Thailand, Vietnam, Brazil and Indonesia where the disease is endemic.

26 August 2011 Last updated at 12:02 ET


Mosquitoes 'disappearing' in some parts of Africa

By Matt McGrath Science reporter, BBC World Service


A mosquito feeding Mosquitoes are now a rare sight in some parts of Africa

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Malaria blocks 'super-infection'

Malaria-carrying mosquitoes are disappearing in some parts of Africa, but scientists are unsure as to why.

Figures indicate controls such as anti-mosquito bed nets are having a significant impact on the incidence of malaria in some sub-Saharan countries.

But in Malaria Journal, researchers say mosquitoes are also disappearing from areas with few controls.

They are uncertain if mosquitoes are being eradicated or whether they will return with renewed vigour.

Data from countries such as Tanzania, Eritrea, Rwanda, Kenya and Zambia all indicate that the incidence of malaria is dropping fast.

Researchers believe this is due to effective implementation of control programmes, especially the deployment of bed nets treated with insecticide.

But a team of Danish and Tanzanian scientists say this is not the whole story. For more than 10 years they have been collecting and counting the number of mosquitoes caught in thousands of traps in Tanzania.

In 2004 they caught over 5,000 insects. In 2009 that had dropped to just 14.

More importantly, these collections took place in villages that weren't using bed nets.
'Chaotic rainfall'

One possibility for the reduction in numbers is climate change. Patterns of rainfall in these years were more chaotic in these regions of Tanzania and often fell outside the rainy season. The scientists say this may have disturbed the natural cycle of mosquito development.
Continue reading the main story
“Start Quote

It is most likely we will have an epidemic of malaria ”

Professor Dan Meyrowitsch, University of Copenhagen

But the lead author of the study, Professor Dan Meyrowitsch from the University of Copenhagen, says that he is not convinced that it is just the changing climate.

"It could be partly due to this chaotic rainfall, but personally I don't think it can explain such a dramatic decline in mosquitoes, to the extent we can say that the malaria mosquitoes are almost eradicated in these communities.

"What we should consider is that there may be a disease among the mosquitoes, a fungi or a virus, or they're may have been some environmental changes in the communities that have resulted in a drop in the number of mosquitoes"

The research team also found anecdotal evidence that their discovery was not an isolated case.

Prof Meyrowitsch added: "Other scientists are saying they can't test their drugs because there are no children left with malaria.

"They observed this in communities with no large interventions against malaria or mosquitoes. It may be the same scenario that the specific mosquitoes that carry malaria are declining very fast now"

The researchers are unsure if mosquitoes will return to these regions. If they do, one particular cause for concern is the young people who have not been exposed to malaria over the past five or six years since the mosquitoes began to decline.

"If the mosquito population starts coming up again" says Professor Meyrowitsch "and my own assumption is that it will, it is most likely we will have an epidemic of malaria with a higher level of disease and mortality especially amongst these children who have not been exposed."

9 November 2011 Last updated at 20:57 ET


Malaria vaccine hope after blood entry route discovered

By James Gallagher Health reporter, BBC News

[IMG]http://news.bbcimg.co.uk/media/images/56536000/jpg/_56536923_c0080862-mosquito_bite.jpg[/IMG]
Mosquito Malaria is transmitted by mosquitoes


Malaria vaccine trial raises hope
Malaria vaccine trial results promising
Malaria vaccine: Inside look at first human trial

The route all strains of the most deadly malaria parasite use to enter red blood cells has been identified by researchers at the Sanger Institute in Cambridge.

The scientists involved said the finding offered "great hope" for the development of a vaccine, which had the potential to be hugely effective.

Other experts said they were surprised and impressed.

Malaria affects 300 million people each year.

One million die, mostly children in sub-Saharan Africa.

There are many malaria parasites. Plasmodium falciparum is the most deadly and researchers at the Sanger Institute acknowledge it as a "very complex and cunning foe".

It is exceptionally good at evading and bamboozling the immune system. Within five minutes of being bitten by a malaria-carrying mosquito, the parasite is already hiding inside the liver.

It then emerges from the liver at a different stage in its life cycle and infects red blood cells, where it starts reproducing.
Difficulty

The human immune system struggles to build up resistance to malaria and researchers have struggled in the laboratory.

There is still no approved vaccine against malaria. Large scale trials of the most advanced prototype - RTS,S - showed it halved the risk of getting malaria.
Healthy and infected red blood cells The parasite reproduces in red blood cells (infected cell on the right).

This study, published in Nature, looked at the moment the parasite infected a red blood cell.

They were looking for proteins on the surface of Plasmodium and red blood cells which were necessary for the parasite to identify its target and invade.

Others had been found before, but none were universally used.

The team at the Sanger Institute discovered that "basigin", a receptor on the surface on red blood cells, and "PfRh5", a protein on the parasite, were crucial.

In all strains of Plasmodium falciparum tested so far, interrupting the link protected the blood cells from attack.

One of the researchers, Dr Julian Rayner, said: "We were able to completely block invasion using multiple different methods, using antibodies targeting this interaction we could stop all invasion of red blood cells.

"It seems to be essential for invasion."

The plan is to develop a vaccine which will prime the immune system to attack PfRh5 on the parasite

Fellow researcher Dr Gavin Wright said a vaccine would have great potential as the target was so essential.

"As a starting point for developing a vaccine you couldn't hope for better," he said.

Prof Adrian Hill, director of the Jenner Institute at Oxford University, said that after 25 years studying malaria he was "surprised" and "intrigued" by the findings.

He said textbooks and academic research suggested that if you blocked one pathway into the red blood cells, the parasite would choose another.

He added: "It remains to be seen how easy it will be to translate into a vaccine, but [for blood stage vaccines] PfRh5 is now at the top of the list.

"Vaccine candidates will come. If I had to bet, I'd say you'd get some partial efficacy from it."

GM Mosquitoes Bite



The critical problem with new experiments in using genetically engineered insects to fight malaria and dengue.

By Ed Yong|Posted Monday, Nov. 14, 2011, at 2:26 PM ET
Mosquito sucking blood Are genetically modified mosquitos the future of malaria-prevention?

Photograph by Tom Ervin/Getty Images

In the Cayman Islands, genetically modified mosquitoes are on the prowl. The insects are all male, and they’ve been engineered so that all their offspring die before reaching adulthood. By having sex with local females, they could father a new generation that perishes prematurely, before it gets the chance to spread diseases like dengue fever.

These GM insects, engineered by Luke Alphey at the University of Oxford, are part of a growing number of initiatives designed to fight disease by pitting mosquitoes against mosquitoes. Alphey’s tactic of breeding mosquitoes that beget unfit larvae is just one approach. Some groups are trying to make the insects more resistant to the disease-causing parasites they carry. Others have loaded them with life-shortening bacteria that outcompete those parasites. While some scientists warn of the unintended consequences of releasing such insects into the wild, others acknowledge that we need innovative new strategies for tackling mosquito-borne diseases like malaria and dengue fever, which affect hundreds of millions of people every year. (Figures for mosquito-borne illness are notoriously unreliable, but the World Health Organization estimates that each year there are 247 million cases of malaria, causing 881,000 deaths, and 50 million instances of dengue.)

But all of these recent attempts to turn mosquitoes into malaria- and dengue-killing machines have something in common: The modified mosquitoes need to have lots of sex to spread their altered genes through the wild population. They must live long enough to become sexually active, and they have to compete successfully for mates with their wild peers. And that is a problem, because we still know surprisingly little about the behavior and ecology of mosquitoes, especially the males. How far do they travel? What separates the Casanovas from the sexual failures. What affects their odds of survival in the wild? How should you breed the growing mosquitoes to make them sexier? Big question marks hang over these seemingly straightforward questions.
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Heather Ferguson from the University of Glasgow studies mosquito ecology. She views the knowledge gap in this field as a significant obstacle that stands in the way of the GM-mosquito initiatives. History tells us how dismally such initiatives can fare if they are not constructed on solid ecological foundations. In the 1970s and 1980s, several groups tried to control the mosquito population by releasing sterile males that would engage females in fruitless sex. The vast majority of the experiments failed.

Their poor performance is often blamed on the fact that the males were sterilized with damaging doses of radiation. But they had many other disadvantages. Lab-bred mosquitoes are frequently reared in large, dense groups, which produces smaller, less competitive individuals. The artificial lights of a lab could also entrain their body clocks to the wrong daily rhythms, driving them to search for mates at the wrong time of the day. And in several cases, the modified males ignored the wild mosquitoes and preferred to mate with their lab-reared kin instead. These problems went unnoticed in lab tests, where the modified mosquitoes were compared with unaltered ones that had been raised in the same conditions. They seemed to be perfectly competitive, but they proved to be feeble challengers to their wild peers.

Given that we ended up with puny, frail mosquitoes that looked for the wrong mates at the wrong times of the day, it is no wonder that most of these early experiments in modifying mosquitoes failed. Compare this example to the case of the citrus-eating medfly, a pest that scientists also tried to control by releasing sterile males in the early 2000s. Just like mosquitoes, mass-reared medflies initially lost out to their wild peers. But scientists realized they could improve the medflies’ reproductive chances by feeding them lots of protein, which gives them energy for mating hunts, or ginger root oil, which produces a female-attracting scent. These simple measures had a big impact on the programs, which have successfully controlled medfly outbreaks in North and South America.

The new generation of GM-mosquito researchers learned from the failed experiments of the ‘70s and ‘80s and is trying to assess the competitiveness of its modified insects in the wild. Alphey’s group found that the ones released in the Cayman Islands fathered about10 percent of the local eggs within a few weeks. They were about half as successful as wild mosquitoes, which sounds poor, but is actually better than a lot of other modified insects, including the successful sterile medflies. The team has suggested that it could compensate for the males’ shortcomings by simply releasing more of them.

Even if that works, it would still be better to make the GM mosquitoes as competitive as possible from the outset. The longer these programs run, the greater the odds that female mosquitoes will simply evolve to avoid the GM males. Again, there is historical precedent. In the 1970s, Japan tried to control the melon fly by releasing large numbers of sterile males. These efforts continued for many years before the females gained the ability to recognise and avoid the interlopers. The message is clear: We cannot afford a guerrilla war with disease-carrying insects. We need shock-and-awe tactics that have a big impact in a short period of time. And to achieve that, we need to plug the gap in our knowledge of mosquito ecology.

Unfortunately, Ferguson says, “A lot of the knowledge gaps that hindered previous attempts still remain.” In a recent review, she noted, “We have made substantially more headway in understanding the reproductive biology of species with no direct public health or economic importance, such as Drosophila, fur seals and blue tits, than we have done for this vector that kills millions.”

This crucial ecological research on mosquitoes is trapped in a financial no-man’s land. Organizations that fund basic research into issues like how insects behave assume that biomedical agencies will foot the bill, while these agencies are more likely to prioritize research with more obvious and immediate clinical impact. But the necessary ecological studies would not be expensive. Ferguson estimates that it would take just $500,000 to fund 10 students in the field, an act that “could easily quadruple our knowledge of this area within a few years.”

For example, in 2008, her student Kija Mg’Habi worked in an isolated, malarious part of Tanzania and discovered that among Anopheles gambiae (a species that carries malaria), the medium-sized males get the most sex. You might expect the biggest males to outcompete their smaller rivals, but they were actually six times less successful. This is exactly the type of information you need if you want your modified mosquitoes to outcompete their natural brethren.

Now, several scientists are trying to learn more about mosquitoes by setting up “semi-field studies.” These large outdoor spaces, enclosed by nets, are like mosquito aviaries. They should allow scientists like Ferguson to study large numbers of mosquitoes, both normal and modified, under natural but controllable conditions. These studies will not only be useful as testing grounds for GM strains; they should also start to provide some long-missing information about our mosquito adversaries. It may not be as sexy as modifying genes, but ecology is tantamount to knowing your enemy, and that surely is a cornerstone of victory.

20 December 2011 Last updated at 09:00 ET


New approach to malaria vaccine revealed by Oxford researchers

By Helen Briggs Health editor, BBC News website


Mosquito Malaria is caused by parasites injected into the blood by infected mosquitoes


Route of malaria's success found
Malaria vaccine trial raises hope

A potential new malaria vaccine has shown promise in animal studies, according to research.

An Oxford University team is to start safety trials in human volunteers after lab tests showed the vaccine works against all strains of the parasite.

UK scientists recently found the route malaria uses to enter blood cells.

They hope to target this pathway in a new approach to developing a vaccine against malaria, which kills hundreds of thousands of people a year.

Several potential malaria vaccines are already being tested in clinical trials; although no vaccine has yet been licensed for use.

Early clinical trials in Africa suggest a vaccine known as RTS,S appears to protect about half of people vaccinated from malaria.

While these results are encouraging, some scientists believe a more effective vaccine is needed to fight the disease.

One possibility is to exploit a recently-discovered potential weakness in the parasite's life cycle.

A team at the Sanger Institute found in November that a single receptor on the surface of red blood cells and a substance known as "PfRh5" on the parasite are crucial to the success of malaria in invading blood cells.
Continue reading the main story
Malaria

Malaria killed about 781,000 people in 2009, mainly children and pregnant women, according to the World Malaria Report 2010
Malaria is caused by parasites injected into the bloodstream by infected mosquitoes
The most deadly form, Plasmodium falciparum, is responsible for nine out of 10 deaths from malaria
Vaccinating against malaria is thought to be the best way to protect populations against the disease
No licensed vaccine is currently available.
Source: Wellcome Trust

Early lab tests suggest a vaccine against the protein may prove effective, at least in animals.

Dr Sandy Douglas is a Wellcome Trust Clinical Research Training Fellow from the University of Oxford and first author on the study, published in the journal, Nature Communications.

He told the BBC: "We have found a way of making antibodies that kill all different strains of malaria parasites. This is still early phase research in animals. The next step is to do clinical trials in people."

If safety tests of the vaccine prove successful, clinical trials in patients could begin within the next two to three years, says the Oxford team.

Dr Gavin Wright, from the Wellcome Trust Sanger Institute, said recent findings on how the malaria parasite invades red blood cells were unexpected.

Dr Wright, a co-author on both studies, added: "It revealed what we think is the parasite's Achilles heel in the way it invades our cells and provided a target for potential new vaccines."

Encefalitis del Valle de Murray

Commons-emblem-notice.svg

Encefalitis del Valle de Murray
Clasificación de los virus
Grupo: IV (Virus ARN monocatenario positivo)
Familia: Flaviviridae
Género: Flavivirus
Especie: virus de la encefalitis de Murray Valley
virus de la encefalitis de Murray Valley
Clasificación y recursos externos
CIE-9 062.4
Wikipedia no es un consultorio médico Aviso médico

La encefalitis del Valle de Murray es una infección virica transmitida por mosquitos, causada por el virus de la encefalitis de Murray Valley (MVEV), un miembro del género Flavivirus, de la familia Flaviviridae, los primeros casos se produjeron en 1917 y 1918.
Contenido
[ocultar]

1 Presentación
2 Clonado
3 Véase también
4 Referencias

[editar] Presentación

La mayoría de las infecciones por MVEV, son asintomáticas, aunque un grupo de los infectados puede llegar a desarrollar una forma leve de la enfermedad con síntomas de fiebre, dolor de cabeza, náuseas y vómito y sólo una pequeña cantidad llega a desarrollar la encefalitis como tal. En efecto, ensayos serológicos que midieron los nivel de anticuerpos anti-MVEV dentro de la población se estima que sólo 1 de cada 800-1000 de todas las infecciones resulta en una encefalitis clínica. El periodo de incubación después de la exposición al virus dura entre 1 y 4 semanas. Después de la infección, la persona tendrá inmunidad de por vida en contra del virus. Cuando un paciente comienza con sintomatología de encefalitis y ha estado presente en áreas endémicas, se puede confirmar el diagnóstico con estudio serológico buscando una elevación en los anticuerpos específicos de MVE.1 De aquellos que contraen la enfermedad, uno de cada cuatro mueren.2
[editar] Clonado

Sus estudios científicos genéticos de la MVEV fueron facilitados con la construcción y manipulación de un clon infeccioso cADN del virus. 3 Las mutaciones en la envoltura génica se vincularon con la atenuación de l aenfermedad en modelos de infección en ratas.
[editar] Véase también

Encefalitis viral

[editar] Referencias

? Error en la cita: El elemento <ref> no es válido; pues no hay una referencia con texto llamada factsheet
? «Deadly mosquito disease suspected», ABC News (Australia), 15 de mayo de 2009. Consultado el 16-05-2009.
? Hurrelbrink RJ, Nestorowicz A, McMinn PC (1 de diciembre de 1999). «Characterization of infectious Murray Valley encephalitis virus derived from a stably cloned genome-length cDNA». J. Gen. Virol. 80 ( Pt 12) (12): pp. 3115–25. PMID 10567642.


http://es.wikipedia.org/wiki/Encefalitis_del_Valle_de_Murray