• Shruti GOCHHWAL

What To Know About the Dengue Causing Aedes Aegypti Mosquito

The dengue fever aedes, like most mosquitoes, thrive in humid tropical and subtropical climates like India and are commonly found in the region. This causes a lot of health-related problems such as mosquitoes acting as vectors of some of the most dangerous or fatal diseases in the world.

The subgenus-stegomyia of the Genus- Aedes contains two important vectors like Aedes aegypti and Aedes albopictus that cause harmful diseases like dengue and chikungunya.

More significantly, the dengue fever aedes aegypti mosquito is one of the biggest causes of vector-borne diseases in the world, infecting around 390 million people yearly.

Lifecycle Cycle

The mosquito undergoes a complete metamorphosis process in four stages:

1)   Egg

Duration: 2-7 days [Two days in a warm climate, seven days in colder climates]

After taking a blood meal, a female mosquito produces around 100 to 200 eggs per batch and lays up to five batches during its lifetime. All the eggs are laid separately and not at once.

Once produced, the eggs are laid on damp surfaces or places where rainwater collects like:

  1. Barrels

  2. Drums

  3. Jars

  4. Pots and buckets

  5. Flower vases

  6. Tanks

  7. Discarded bottles

  8. Tires

  9. Water cooler

Appearance of the egg:

  1. Smooth

  2. Long

  3. Ovoid shaped

  4. One millimeter long

  5. White in color but turns gray within a few minutes after getting laid.

Adaptation: If the area where the egg has been laid is dry, then the eggs can survive for several months or years until the medium becomes damp again. This kind of adaptation increases the survival of this species. This makes it very difficult to eradicate such mosquitoes and the diseases that it spreads.

buckets of water

Breeding areas, Credit: Pikist


2)   Larva

Duration: Around 4 days

After the eggs hatch, the larvae will receive the necessary nutrition by feeding on the organic organisms present in the water.

Larval development is temperature-dependent. The larvae pass through four instars, spending a short amount of time in the first three, and up to three days in the fourth instar. Fourth instar larvae are approximately eight millimeters long.

Usually, males develop faster than females and thus enter the pupa stage earlier.

Adaptations:

  1. In cool temperatures, the developing mosquito can remain in its larval stage for months so long as the water supply is sufficient.

  2. The larvae can swim from the surface of the container to the bottom if it is disturbed or is unable to survive on the surface.

3)   Pupa

Duration: 2 days

The larvae enter the pupal stage after the fourth instar stage. At this point, they are mobile and responsive to any stimuli.

They do not feed during this stage of development until the adult stage.

4)   Adult stage

Duration: 14-30 days depending on climate conditions.

Once mosquitoes have turned into adults, they emerge out by:

  1. Ingesting air

  2. Expanding their abdomen which splits the pupal case.

 However, from this stage, the male and female life cycle is quite different.

Male and Female after the Adult stage

Once the male reproductive system has been developed, they start to find females to mate with by attracting them with their large antennae.

After mating, they will only live for 3-5 days where they continue to feed on plant nectar and fruit juices.

However, since females are responsible for reproducing and laying eggs,  they need to consume blood meals and hence go on to bite humans.

dengue fever aedes

Aedes mosquito, Credit: Pixnio


The Growth Rate

Keeping in mind with close reference to the life cycle and nature or laying eggs, here a mathematical calculation to give a clearer idea on the mosquito population.

The first day

1 female x 300 eggs = 150 males, 150 females

After 2 weeks an extra 150 adult females will lay another 150 females each.

After 6 weeks after development

 150 females x 150 females = 22.500 females

After 12 weeks

22500 females x 150 females = 3.375.000 females

After 18 weeks

 3.375.000 x 150 females = 506.250.000 females and they all need blood to feed!

Transmission of Dengue Virus

How does the mosquito get infected?

The mosquito gets infected when they feed on the blood of the virus-infected person.

How do humans get infected with dengue?

Once the mosquito is infected, it undergoes an 8-10 days incubation period but during this period, they are capable of transmitting the dengue fever aedes virus to humans during their next blood meals and are capable of doing so throughout its remaining lifetime.

Once infected, the virus circulates and multiplies in the blood for 2-7 days.

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