Dengue infection is transmitted from one person to other by the bite of an infected female Aedes mosquito. Dengue fever (DF) is a viral infection caused by any of the four types of dengue virus (DENV-1 to DENV-4). Aedes aegypti is the commonest vector of dengue fever. Other Aedes species which can also act as potential vectors are Ae. Albopictus, Ae. Polynesiensis and Ae. Niveus. In India, the potential vectors are Aedes aegypti (the main vector in most urban areas) and Aedes albopictus (vector in few areas of southern India). [Read: Genetics of Dengue Fever]
The Aedes mosquito: The Aedes mosquito (vector of dengue fever) becomes infected after biting an infected person. The dengue virus spreads when the infected mosquito bites a healthy person. To get one full blood meal, the mosquito bites several persons, and infects all of them. The mosquito remains infected for the rest of its life and can transmit the infection to its progeny of mosquitoes through eggs ( transovarial transmission).
Some facts about the Aedes mosquito
- Only the female Aedes mosquito bites and transmits the infection after biting an infected person.
- Average life span of Aedes mosquito is about 2 weeks and in the rainy season, when survival is longer, the risk of virus transmission increases.
- It can fly for a limited distance of 400 metres. It usually spreads over vast distances due to humans travelling far and wide.
- The virus multiplies inside the mosquito and the mosquito can transmit the infection (that is becomes infective) approximately 7 days after biting an infected person.
Feeding Habit of Aedes mosquito
- Aedes is a day biting mosquito with the peak biting time at dawn (2 hours after sunrise) and dusk (a few hours before sunset).
- It is found mainly in and around domestic areas (households, construction sites and factories) and bites human beings in domestic and peridomestic areas.
- It often bites repeatedly and needs to bite several persons to get one full blood meal.
- Resting Habit of Aedes mosquito
- It lives and rests in dark, cool places such as in closets, under beds, behind curtains, and in bathrooms.
- Outside the house it rests in cool and shady places.
Potential Breeding Sites for Aedes mosquitoes
The Aedes mosquito breeds in water collections in and around human living areas (households, construction sites and factories) such as:
- Water storage containers (drums and barrels, earthen pots and jars).
- Desert Coolers.
- Unused tyres.
- Coconut shells.
- Disposable cups.
- Open overhead tank, open cement tanks, curing tanks.
- Water reservoir.
- Suburban slums.
- Construction sites.
- Pools.
- Rain barrels.
- Potted plant trays.
- Birdbaths
The female mosquito lays eggs in these man-made water receptacles in and around your house and neighbourhood. The female mosquito lays eggs three times in its lifespan and each time it lays about 100 eggs. If the surrounding and atmosphere are compatible, the eggs develop into adult form in as short as seven days. But in low temperatures, it may take several weeks to become an adult. [Read: Treatment of Dengue Fever]
Dengue fever is a major public health problem in several parts of the world. As there is no specific treatment for dengue, prevention has an important part in control of dengue fever. Major focus on prevention centres on avoiding mosquito bites and controlling and eliminating mosquito breeding sites.
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