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Oxford researchers offer sterile male mossies to combat dengue
- Written by Super User
A media conference on Sterile Male Mosquitoes as a Way to suppress Dngue in Sri Lanka was held at Kingsburry hotel on Oct. 22. Managing Director of Omega Global Holdings Pvt. Ltd. Manik Suriyaaratchi addresses journalists while officials of Oxitec look on. Pic by Kamal BogodaBy Don Asoka Wijewardena
Oxitec Field Studies Director Kevin Gorman announced yesterday that Oxitec Company formed by researchers from the Oxford University had developed a technology to render male mosquitoes infertile so as to eliminate the dengue vector.
Gorman told a media briefing in Colombo that, first of all, it was essential to understand that male mosquitoes did not bite or pose any threat to humans.
Gorman said that the genetically sterile male had been developed and refined over ten years and successfully used in several parts of the world. For instance, in the Cayman Islands, in the Caribbean, the technology had helped suppress the dengue mosquito population by over 80 per cent within four months. In Brazil the suppression rate ranged from 85 per cent to 96 per cent in four to six months.
Those results showed the potential for the sterile male technology to rapidly and sustainably reduce the dengue carrying mosquito population without exposing the humans and animals living in the area to potentially toxic chemical pesticides, Gorman said.
Omega Global Debug Solution (Pvt) Ltd Managing Director Manik Suriyaaratchi said that environmental compatibility was a hallmark of sterile male mosquitoes. There were no toxins involved and, therefore, there was no potential for environmental contamination because non-biting male mosquitoes would fly in search of females.
They would reach areas where traditional fogging techniques could not reach––behind walls, locked doors and on construction sites.
She said that the dengue carrying Aedes aegypti population was not invasive or endemic to Sri Lanka.
Oxitec and its local agent Omega Global Debug solution are now negotiating with the Health Ministry to introduce the sterile male mosquito to Sri Lanka.
Dengue Fever Symptoms
According to data from epidemiology unit of Sri Lanka, the number of total cases recorded for year 2009 is 32713. Most affected district was Kandy. Colombo, Gampaha and Kaluthara districts which have been susceptible in the past have also recorded a high rate of infection and deaths.
- Incubation period is 2-7 days.
- All haemorrhagic fever syndromes begin with abrupt onset of fever (39.5–41ºC) and myalgia.
- Fever is often biphasic with two peaks.
- Fever is associated with frontal or retro-orbital headache lasting 1–7 days, accompanied by generalised macular, blanching rash.
- Initial rash usually fades after 1–2 days.
- Symptoms regress for a day or two then rash reappears in maculopapular, morbilliform pattern, sparing palms and soles of feet. Fever recurs but not as high. There may be desquamation.
- DF cases experience severe bony and myalgic pain in legs, joints and lower back which may last for weeks (hence breakbone fever).
- Nausea, vomiting, cutaneous hyperaesthesia, taste disturbance and anorexia are common.
- Abdominal pain may occur and if severe suggests DHF pattern.The signs of dengue fever/ Dengue haemorrhagic fever are- High fever, rash, hypotension and narrow pulse pressure, poor capillary refill.
- There may be hepatomegaly and lymphadenopathy.
- A tourniquet placed on an arm may induce petechiae in early DHF cases. DHF sufferers exhibit a bleeding tendency as evidenced by petechiae, purpura, epistaxis, gum bleeding, GI haemorrhage and menorrhagia. There may be pleural effusion, ascites and pericarditis due to plasma leakage.
- Petechiae are best visualised in the axillae.
- Flushing of head and neck.
- Tender muscles on palpation.
- Periorbital oedema and proteinuria may be present.
- Maculopathy and retinal haemorrhages may also occur.
- DSS pattern cases progress through DHF until profound shock due to severe hypotension is present.
- CNS involvement e.g. encephalopathy, coma, convulsions.
- Hepatic failure: Means failure of the liver
- Encephalopathy: Means damage to the brain causing fits, loss of consciousness and confusion- Myocarditis – Inflamation of heart muscles
- Disseminated intravascular coagulation - Damage to blood vessels and blood cells causing problematic bleeding and clottingDengue can cause death
- Infection may be confirmed by isolation of virus in serum and detection of IgM and IgG antibodies for Dengue by ELISA, monoclonal antibody or haemagglutination
- Molecular diagnostic methods such as reverse-transcriptase-PCR are increasingly being used.
- Chest X-ray may show pleural effusion.
- Nutritious diet and lot of liquids, But avoid red and brown foods and drinks like coffee, chocolate, grapes etc as it may misinterpret vomiting as blood stained vomitus.
- Fever control with paracetamol, tepid sponging and fans. Aspirin should be avoided.
- Need to seek advice from a qualified medical practitioner if fever lasts for more than 2 days
- Hospital managemnt includes intravenous fluid resuscitation with close monitoring. Haemorrhage and shock will require Fresh Frozen Plasma, platelets and blood. Intensive management with inotropes of the shock syndrome may be required in severe DHF/DSS cases.
- Anti-mosquito public health measures such as reducing breeding sites ( flower pots, fish tanks,tires, coconut shells, tins, water collecting plants, gutters which can collect water) and good sewage management
- Insecticides to destroy the larvae
- Mosquito nets can be used during day time as the Aedes mosquitoes is day-biting.
- Mosquita repellents
- There is a bacteria called Bacillus thuringiensis which destroy the mosquito larvea