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Can genetically modified mosquitoes fight dengue?

MosquitoesA British company has approached Indian authorities seeking permission for technology trials of a certain genetically-modified mosquito claiming it will fight dengue menace. The modified male mosquito named '513A' will have a gene that ensures its offspring dies before reaching adulthood (in 2-5 days) and thus control breeding of dengue spreading mosquitoes.

This genetically-modified mosquito has been tested in Brazil, where dengue emerged as a big worry during the recently concluded World Cup Football tournament, and the Cayman Islands.

UK-based Oxitec, an Oxford University spin-out which develops technologies for controlling insects, has approached the Indian government for necessary approvals to begin trials for GM mosquitoes here.

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A company spokesperson told PTI from Oxford that the technology can be made available to public health authorities in India to help suppress the mosquitoes that spread dengue. 'Oxitec is working with GBIT, a privately held Indian company that specialises in developing and commercialising novel technologies in health and agriculture, with a view to introducing this technology for dengue vector control in India,' the spokesperson said. Thousands of dengue cases are reported every year in India.

'In due course, we would like to use the same approach for the main vectors of malaria but this work is at a very early stage,' he said.

In the laboratory, the activity of this gene can be controlled by giving mosquitoes the antidote 'tetracycline'.

With regard to regulatory clearances, GBIT has already received nod for contained laboratory-based studies. Besides, permission for larger technology trials has been sought from the Review Committee for Genetic Manipulation (RCGM).

Field based studies would only begin following appraisal and approval by the relevant national bio safety committees, RCGM and Genetic Engineering Approval Committee (GEAC). RCGM and GEAC come under the Ministry of Environment and Forests.

'We expect a large-scale trial to be the next step; however, the timing is entirely within the hands of the RCGM,' the official noted.

As per Oxitec, dengue mosquito can also carry other diseases such as Chikungunya or Yellow Fever.

These GM male mosquitoes can mate only with females of the same species (dengue spreading), so that it is exclusively targeted to the dengue mosquito with no effect on other insect species. 'Every wild female which mates one of our modified males will have offspring who carry the gene and without the antidote, they won't survive. 'In this way, by repeatedly releasing Oxitec males, we can drastically reduce or even locally eliminate the dengue mosquito population,' he said.

What is dengue?

It is a tropical disease, usually transmitted by mosquitoes and the common symptoms include fever, headache, muscle and joint pains and skin rash. There is no vaccine for dengue and the only way to reduce infections is to improve hygiene levels so as to prevent mosquito-bites and prevent mosquitoes from breeding. It's particularly difficult to create a vaccine because it's caused by different viruses and there are no animal models available for testing. The disease kills over five thousand Indians every year and is a seasonal threat, particularly during the monsoon seasons.

What are the symptoms of dengue?
Characterized by severe flu-like symptoms, dengue affects infants, children and adults alike and could be fatal. The clinical manifestations of dengue vary with the age of the patient. A person suffering from high fever in the range of 40 C/ 104 F, accompanied by any two of the following symptoms could be suffering from dengue:

Symptoms usually last for 2-7 days. Dengue could progress to severe dengue, a potentially fatal complication, causing leaking of plasma, fluid accumulation, respiratory distress, severe bleeding and organ impairment.

The warning signs to look out for occur 3-7 days after the first symptoms along with a decrease in temperature are:

  • Severe abdominal pain
  • Persistent vomiting
  • Rapid breathing
  • Bleeding gums
  • Blood in vomit
  • Fatigue, restlessness

The next 24-48 hours of the critical stage can be lethal; proper medical care is needed to avoid complications and risk of death.

Once you see any of the above symptoms, do visit a doctor as soon as possible. The diagnosis of dengue fever is usually made when a patient exhibits the typical clinical symptoms of headache, fever, eye pain, severe muscle aches and petechial rash. Usually if a patient is from an area that has a huge population of mosquitoes, dengue can be suspected. A blood test to diagnose people with dengue fever, called the DENV (Detect IgM Capture ELISA) may also be used.

If untreated, the most serious complication is dengue haemorrhagic fever (DHF), in which blood vessels start to leak and cause bleeding from the nose, mouth, and gums. Untreated DHF can lead to dengue shock syndrome (DSS), which is lethal in 90% of cases unless promptly and correctly treated, in which case fatality rates can fall as low as 1%, depending on quality of treatment.

Recently there have been news stories on a dengue strain that affects the liver. This condition is also called dengue hepatitis. It leads to severe organ malfunction and in some cases even organ failure. In the case of dengue hepatitis, fever lasts longer, often for more than a week, and leaves the patient extremely exhausted. An indication of this condition, according to experts is the sudden rise in SGOT (Serum Glutamic Oxaloacetic Transaminase) and SGPT (Serum Glutamic Pyruvic Transaminase) levels, sometime almost 20 times higher than the normal level. Dengue hepatitis is characterized by high fever, lasting more than a week, extreme weakness. The blood tests show an increase in SGPT and SGOT levels, a drop in platelet count and WBCs.

Medication

Because dengue fever is a viral infection, there is no specific treatment for the condition. The patient should seek medical advice and drink plenty of fluids. Symptomatic relief can be sought using NSAIDs (Non-steroidalanti-inflammatory drugs) such as Paracetamol. But drugs such as aspirin or ibuprofen should not be taken since they can increase the risk of bleeding. For severe dengue, medical care by experienced physicians can frequently save lives. It is important to maintain the fluid volume of the patient for recuperation of the patient.

Prevention

Dengue is a communicable diseases spread by mosquitoes from one human to another. So, the only way it can really be prevented is by avoiding mosquito bites. One can make sure all egg-laying habitats of mosquitoes like open and stagnant water source are cleaned up. If there are any open water sources you cannot eliminate, cover them and apply appropriate insecticides. Use protection such as window screens, long-sleeved clothes, and insecticide treated materials, coils and vaporizers. (Read: Prevent dengue with these 10 practical tips)

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With inputs from PTI

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