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by Aryadasa Ratnasinghe

Dengue is a tropical viral disease caused by the bite of mosquitoes Aedes agyptii and Aedes alobopictus, which go in search for their blood meal, either in the morning or in the evening before dusk falls.

The incubation period (the time between infection and appearance of symptoms) is 5 to 7 days. The breeding grounds for mosquitoes are untended swamps and dumping grounds, murky green pools of stagnant water and littered yards, but the dengue mosquito breeds in fresh water. With the rains continuing, there shows an increase in the spread of the disease.

Dengue is also known as breakbone fever, dandy fever and saddleback fever. It is a preventable disease, provided necessary water, and what is most important is public awareness of the preventive measures that have to be taken to prevent the disease raising its ugly head. The government alone cannot handle this situation, without public co-operation in mutual participation.

extremities

Mosquitoes are often the harbingers of lethal diseases, such as dengue, malaria, filaria and Japanese encephalitis. In Sri Lanka, many are afflicted with diseases transmitted by mosquitoes, and the one under discussion is dengue which is of two types. One is Dengue Fever and the other is Dengue Haemorrhagic Fever, the last being more deadlier than the other, and requires immediate hospitalisation, before it turns fatal.

The general symptoms of dengue are high fever associated with chills and headache, retro-ocular pain (pain behind the eye-balls), nausea, abdominal pain, pain through the muscles and joints, rash on the face, trunk and the extremities, vomiting and the rash resembles measles. This condition, usually, subsides in 3 to 4 days, and patients recover, but some may develop Dengue Haemorrhagic Fever, where the symptoms are similar to Dengue Fever.

Dengue Haemorrhagic Fever is a lethal condition known as Dengue Shock Syndrome. In addition to bleeding manifestations, petechial rash (red or purple spots on the skin), bleeding from nose and gums, brown or black coloured vomitus or faeces, severe and continuous stomach pain, enlargement of the liver and other conditions relevant to the disease appear. Coldness and paleness of the body, restlessness and drowsiness, quick breathing and increase in the pulse rate, have been cited as shock symptoms of the disease. Under such acute conditions, the patient needs hospitalisation than outdoor treatment.

Dengue affects all and sundry, but it is severe in children and youth. A little loss of plasma (the liquid part of the blood) in a small child is relatively a high proportion when compared with the body size. It is one of the reasons why children become victims to the disease, where the mortality rate is about 60 per cent, than adults. The best way to fight the viral disease is to prevent breeding grounds for mosquitoes, where they multiply in thousands and go in search of blood. It is the female that sucks blood and transmits the vector.

Personal protection is also vital as well as essential to keep the mosquitoes at bay. When there is an epidemic of dengue, people of all ages become exposed to the hazards which they cannot easily control. The use of mosquito-nets, mosquito-repellent creams, aerosols, mats and coils have become the popular means of protection today, to escape from mosquito-borne diseases. 'No coil, no sleep' means that the coil has become the popular means of protection in most homes, to have a good and undisturbed sleep. It has, today, become the most indispensable household item, next to food.

breeding ground

Contrary to the popular belief, mosquito breeding grounds are not confined to outdoor areas alone. Even a home can become a deadly breeding ground for the dengue mosquitos, because some of them breed in any container that can collect water up to 7 days. Therefore, it should be borne in mind that the best way to keep the mosquitoes at bay, is to keep the surroundings of every home clean of stagnant water and other breeding facilities. All waste products should be buried or burnt, king-coconut husks and coconut shells should be destroyed or cut into pieces to prevent accumulation of water, and the same with discarded empty tins.

Salt should be added to water in flower vases and ant-traps and water should be changed frequently to destroy larvae deposited therein. Tyres placed on roof tops as weights should be filled with sand, not to allow rain water to become stored therein. medical advice

Fallen leaves and debris blocking the drain-pipes and gutters should be cleaned at least weekly. It is very important not to throw polythene bags out of doors because they provide favourable grounds for mosquitoes to breed in water accumulated therein.

According to medical advice, if dengue fever is suspected, the patient must take complete bed rest, drink lot of fluids, and aspirin should not be given to low down fever. But, paracetamol is recommended. As a means of prevention, people must avoid mosquito bites in high-risk areas in epidemic proportions, and use aggressive repellents, if mosquitoes are around waiting their turn to have their blood meal.

Still, there is no vaccine currently available to be used as a prophylactic treatment against dengue.

Because mosquitoes have their choice for small areas of stagnant water, they prefer old cans, discarded tyres, empty bottles newly filled with good water, as their haven to breed and multiply.

Businessmen who advertise different brands of mosquito coils, through mass media, speak highly of their products, which contains 2 per cent of chemicals and 98 per cent of saw-dust or charcoal, which keep burning throughout the night, or exceeding up to 12 hours. They says they are highly effective, economical and ubiquitous, being freely available in the market, from supermarkets to wayside boutiques. It is said that active ingredient capable of keeping the mosquitoes away is biodegradable or perishes without accumulation on surfaces.

Although medical men say that dengue is a preventable disease, no one seems to have a hand in it. There are proposals, arguments, 'sramadanas' (voluntary services) and suggestions to combat the disease, but they all become lost into oblivion. The mosquitoes proudly laugh at us for our weakness and have a good blood meal at the expense of the donor, and due to his negligence. They mock at the coil or mat but have their meal to satisfy their appetite. As Aedes species are day-time biters, nets and coils play a very small role, in the prevention of dengue.

The only way open to eradicate dengue is to keep the environment clean of swampy grounds, because there is no immunisation to prevent the disease spreading in epidemic proportions. Apart from removing receptacles, a 'fogging programme' with the insecticide malathion to kill the adults would prove effective.

The mosquito is also known as gnat. It is a small slender fly with a piercing proboscis, lays eggs in water, usually blood-feeding females act as intermediate host to diseases which they spread. The vector Aedes is found in coastal and riverside habitats. Mosquitoes belong to the natural order Diptera and to the family Culcidae.

The world opinion is that we cannot eradicate mosquito-borne diseases so long as there are favourable breeding grounds which is common everywhere. Even scientific approaches have proved futile. But it does not mean that it is an impossibility and we cannot roll in back.

There is nothing impossible other than miracles. What is needed is the united effort to clamp down the outbreak of dengue in epidemic proportions. Recently, dengue has taken its toll and many succumbed to the deadly disease.

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