'Bug' could combat dengue fever

Started by nithyasubramanian, Jan 04, 2009, 12:07 AM

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nithyasubramanian



Humans could be protected from dengue fever by infecting the mosquitoes carrying it with a parasite which halves their lifespan, say researchers.
Australian scientists, writing in the journal Science, found that Wolbachia bacteria spread well through laboratory-bred mosquitoes.

Only older mosquitoes pass on dengue - so killing them could cut disease.
Experts said it remained to be seen how well the bacteria would spread outside the laboratory.
The virus might also adapt to survive, they added.

Many thousands of cases of dengue fever occur worldwide each year, mainly in warmer tropical countries.
The virus is passed to humans when mosquitoes carrying it feed on their blood, and while there have been efforts to eradicate them using insecticides, these have been fraught with problems, including the ability of the mosquito to become resistant to the chemicals used.
The potential of Wolbachia as a way of controlling mosquito populations has been suggested for some time, but the latest study offers hope - albeit under laboratory conditions - that it might work.
The researchers from the University of Queensland in Brisbane picked a strain of Wolbachia known to halve the lifespan of its host.
The mosquito which carries the dengue virus is not naturally susceptible to the bacteria, so the researchers adapted it to create a successful infection.

The bacteria can be passed from infected female to offspring, and even though the cost in terms of lifespan should mean that infected insects should die out, Wolbachia has another trick up its sleeve.
It makes subtle changes to infected males which mean they can only produce offspring with infected females.
Older danger
As expected, the infection thrived in the laboratory population of mosquitoes, and halved their lifespan to just a few weeks.
This is potentially significant because, after a mosquito acquires the dengue virus by biting an infected animal or human, there is a period of incubation lasting from a week to three weeks before it can pass on the infection when biting.
This means that only mosquitoes older than this are likely to be dangerous to humans and even these are likely to die swiftly, reducing their ability to infect.
The researchers suggested that the parasite represented a potentially inexpensive way to tackle the problem, particularly in urban areas, where other methods of control were difficult.
Dr Andrew Read and Dr Matthew Thomas, specialists in infectious disease dynamics from the Pennsylvania State University in the US, said "substantial" reductions in disease transmission could occur, but there were still obstacles to success.
"Determining whether it can remove enough infectious mosquitoes will be a challenge," they wrote.

If the bacterial strain chosen was too virulent it would spread very slowly and large numbers of infected mosquitoes might need to be released, they said.
It was also possible that dengue virus strains would adapt to require a shorter incubation period, they said.
Thanks and Regards
- Nithya Subramanian
Kenvivo Communications
http://nithya-subramanian.blogspot.com/

Avishek



Humans could be protected from dengue fever by infecting the mosquitoes carrying it with a parasite which halves their lifespan, say researchers.
Australian scientists, writing in the journal Science, found that Wolbachia bacteria spread well through laboratory-bred mosquitoes.

Only older mosquitoes pass on dengue - so killing them could cut disease.
Experts said it remained to be seen how well the bacteria would spread outside the laboratory.
The virus might also adapt to survive, they added.

Many thousands of cases of dengue fever occur worldwide each year mainly in warmer tropical countries.
The virus is passed to humans when mosquitoes carrying it feed on their blood, and while there have been efforts to eradicate them using insecticides, these have been fraught with problems, including the ability of the mosquito to become resistant to the chemicals used.
The potential of Wolbachia as a way of controlling mosquito populations has been suggested for some time, but the latest study offers hope - albeit under laboratory conditions - that it might work.
The researchers from the University of Queensland in Brisbane picked a strain of Wolbachia known to halve the lifespan of its host.
The mosquito which carries the dengue virus is not naturally susceptible to the bacteria, so the researchers adapted it to create a successful infection.

The bacteria can be passed from infected female to offspring, and even though the cost in terms of lifespan should mean that infected insects should die out, Wolbachia has another trick up its sleeve.
It makes subtle changes to infected males which mean they can only produce offspring with infected females.
Older danger
As expected, the infection thrived in the laboratory population of mosquitoes, and halved their lifespan to just a few weeks.
This is potentially significant because, after a mosquito acquires the dengue virus by biting an infected animal or human, there is a period of incubation lasting from a week to three weeks before it can pass on the infection when biting.
This means that only mosquitoes older than this are likely to be dangerous to humans and even these are likely to die swiftly, reducing their ability to infect.
The researchers suggested that the parasite represented a potentially inexpensive way to tackle the problem and dengue   pills can help, particularly in urban areas, where other methods of control were difficult.
Dr Andrew Read and Dr Matthew Thomas, specialists in infectious disease dynamics from the Pennsylvania State University in the US, said "substantial" reductions in disease transmission could occur, but there were still obstacles to success.
"Determining whether it can remove enough infectious mosquitoes will be a challenge," they wrote.

If the bacterial strain chosen was too virulent it would spread very slowly and large numbers of infected mosquitoes might need to be released, they said.
It was also possible that dengue virus strains would adapt to require a shorter incubation period, they said.




Humans could be protected from dengue fever by dengue pills or prevent them by infecting the mosquitoes carrying it with a parasite which halves their lifespan, say researchers.
Australian scientists, writing in the journal Science, found that Wolbachia bacteria spread well through laboratory-bred mosquitoes.

Only older mosquitoes pass on dengue - so killing them could cut disease.
Experts said it remained to be seen how well the bacteria would spread outside the laboratory.
The virus might also adapt to survive, they added.

Many thousands of cases of dengue fever occur worldwide each year, mainly in warmer tropical countries.
The virus is passed to humans when mosquitoes carrying it feed on their blood, and while there have been efforts to eradicate them using insecticides, these have been fraught with problems, including the ability of the mosquito to become resistant to the chemicals used.
The potential of Wolbachia as a way of controlling mosquito populations has been suggested for some time, but the latest study offers hope - albeit under laboratory conditions - that it might work.
The researchers from the University of Queensland in Brisbane picked a strain of Wolbachia known to halve the lifespan of its host.
The mosquito which carries the dengue virus is not naturally susceptible to the bacteria, so the researchers adapted it to create a successful infection.

The bacteria can be passed from infected female to offspring, and even though the cost in terms of lifespan should mean that infected insects should die out, Wolbachia has another trick up its sleeve.
It makes subtle changes to infected males which mean they can only produce offspring with infected females.
Older danger
As expected, the infection thrived in the laboratory population of mosquitoes, and halved their lifespan to just a few weeks.
This is potentially significant because, after a mosquito acquires the dengue virus by biting an infected animal or human, there is a period of incubation lasting from a week to three weeks before it can pass on the infection when biting.
This means that only mosquitoes older than this are likely to be dangerous to humans and even these are likely to die swiftly, reducing their ability to infect.
The researchers suggested that the parasite represented a potentially inexpensive way to tackle the problem, particularly in urban areas, where other methods of control were difficult.
Dr Andrew Read and Dr Matthew Thomas, specialists in infectious disease dynamics from the Pennsylvania State University in the US, said "substantial" reductions in disease transmission could occur, but there were still obstacles to success.
"Determining whether it can remove enough infectious mosquitoes will be a challenge," they wrote.

If the bacterial strain chosen was too virulent it would spread very slowly and large numbers of infected mosquitoes might need to be released, they said.
It was also possible that dengue virus strains would adapt to require a shorter incubation period, they said.



Dengue fever is a mosquito-borne viral disease that is widespread in Singapore and other tropical countries. It is caused by the dengue virus and is transmitted through the bite of an infected Aedes mosquito.

Dengue fever symptoms include a fever, intense headache, body aches, joint pains, loss of appetite, nausea, vomiting, and skin rashes and mucosal bleeding. There is no specific treatment for dengue fever, but adequate fluid intake and bed rest is important. Most patients recover within two weeks.

However, dengue fever can turn severe, leading to dengue haemorrhagic syndrome and dengue shock syndrome.

According to the World Health Organisation (WHO) 2009 case classification, dengue is classified into dengue without warning signs, dengue with warning signs and severe dengue. It is important to recognise the warning signs such as abdominal pain, persistent vomiting, mucosal bleeding, lethargy and fluid accumulation as it may progress to severe dengue. Even dengue patients without warning signs can develop severe dengue. Dengue fever with warning signs and severe dengue require aggressive emergency treatment and hospitalisation.

The National Environment Agency (NEA) is spearheading the fight against dengue fever in Singapore by raising public awareness about mosquito breeding and destroying existing breeding sites.
How to protect yourself from getting dengue fever
You can protect yourself against dengue fever by taking the following precautions:

Protect yourself against mosquito bites
Prevent mosquito breeding inside and outside your home
Avoid visiting areas prone to mosquitoes
If you live in a neighbourhood identified as a dengue cluster*, or if you are visiting a dengue cluster or a mosquito-prone area, heed the following advice:

1. Apply mosquito repellent, ideally one containing DEET.

Apply it to exposed skin and/or clothing, using enough to cover the entire area. Do not apply it under clothing.
Do not apply it on cuts, wounds or irritated skin.
Do not apply it near the eyes or mouth, and apply sparingly around ears.
When using sprays, never spray directly on the face. Spray it on your hands first and then apply it to your face. Wash your hands afterwards.
Do not allow children to handle a repellent. When using it on children, apply it to your own hands first and then put it on the child. Avoid applying it to children's hands.
Do not use an insect repellent for infants under two months of age.
2. Wear long-sleeves and long pants to cover your arms and legs.

3. Use mosquito nets while sleeping.

"If you or your child gets a rash or any other negative reaction from an insect repellent, wash it off with mild soap and water and stop using the product. Consult a doctor if the condition persists," says Dr Chua Ying Ying.

* A dengue cluster is formed when 2 or more dengue cases occur within 14 days and the homes of the dengue victims are within the distance of 150m. (NEA website)

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