Decoding Dengue

Decoding Dengue

Do you know that  only female species of  Aedes aegypti mosquito can spread dengue or chikungunya? Read about more such important facts to raise your awareness.
By Dr A K Aggarwal

Dengue, a common communicable disease, caused by dengue virus, is characterised by high fever, severe body aches, intense headache and other symptoms.
Dengue fever is spread by mosquitoes called the Aedes mosquitoes which are very tough and bold and can bite even during the day time. Dengue fever occurs more frequently in the rainy season and immediately afterwards (July to October) in India.The most dangerous mosquitoes like Female Anopheles or Aedes aegypti are primarily responsible for spreading dengue. Also, only female mosquitoes can spread dengue or chikungunya.  Males do not bite or spread disease (in fact, males  are not primarily responsible for spreading dengue.
They most commonly infest ponds, marshes, swamps and other wetland habitats. However, they are capable of thriving in a variety of locations and can successfully grow in numbers even when not in their natural habitat. Many species of mosquitoes use containers of water as egg-deposit sites.

Dengue Mosquito’s Life Cycle
Female Aedes aegypti commonly lays eggs on the inner walls of artificial containers. When the containers fill with water, mosquito larvae hatch from the eggs. After developing through four larval stages, the larvae metamorphose into pupas.
Both male and female mosquitoes are nectar feeders, but the females of many species are also capable of hematophagy (drinking blood). Females do not require blood for their own survival, but they do need supplemental substances such as protein and iron to develop eggs. Our blood is essential for mosquitoes as it provides the protein mosquito eggs need for development. While fertilization occurs only after a blood meal, the blood does not fertilize the eggs. Mosquitoes reproduce sexually, and they drink blood. Often, it is only the females which drink blood, and they use this food as fuel for creating eggs. Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. They can transmit disease without being affected themselves.
Aedes aegypti is the species of mosquito which is primarily responsible for spreading dengue.  Other Aedes species such as Aedes albopictus, can also spread dengue and chikungunya, but Aedes aegypti is the main vector and it is this species that is responsible for almost all of the dengue epidemics. Aedes albopictus is often cited as a dengue vector and can indeed spread the disease but it is not very efficient. Other mosquito species bite humans but do not spread dengue fever.

Prevention of dengue fever
Prevention of dengue is mainly targeted towards preventing breeding of mosquitoes and protection from mosquito bites. Following tips will help you in these aspects:
Make sure there is no stagnant water in and around your house. Get the blocked drains cleaned. Fill the ditches. Empty the water from air coolers and flower vases completely at least once in 7 days and let them dry. Remove old containers, tyres, pots, etc.
Tightly cover the water tanks and containers so that the mosquitoes cannot enter them.
If it is difficult to drain the water completely from room cooler, you can add two tablespoons (30 ml) of petrol or kerosene oil for each 100 litres of water. This will prevent the mosquitoes from breeding. Repeat this procedure every week.
Get wire mesh fixed to your doors and windows of the house, so that the mosquitoes cannot enter the room.
Use mosquito repellent creams, sprays, coils or liquids to protect yourself from mosquito bites.
Always sleep under a mosquito net. Also, make sure small children sleep under mosquito net even during the day.
Wear clothes which cover your hands and legs like full sleeves shirt/T-shirt, full pants, socks and shoes.
Use insecticidal spray in the house at least once a week. Don’t forget to spray behind the sofa, bed, curtains, etc.
Keep the surroundings of your house clean. Avoid littering garbage and cover your dust bin or trash can.
Don’t allow wild plants to grow around your house. They act as a hiding place for mosquitoes.
Do remember, that Aedes mosquitoes can bite even during day time. Therefore, you should protect yourself against bite during day time also.
Lastly, make sure that a patient of dengue fever is kept under a mosquito net during the first 5-6 days of illness. This isolation will help in preventing the spread of infection to others in the community.

(The author is Medical Advisor, Apollo Hospital, New Delhi, Professor of Excellence, and Ex Dean, Maulana Azad Medical College, New Delhi)