Aedes aegypti is one of the most important mosquitoes for transmitting diseases to humans, such as dengue, chikungunya and zika. It is also a major cause of human mortality from mosquito-borne diseases worldwide.
Aedes aegypti can found in tropical and sub-tropical areas around the world. It believed that it brought to the Americas and Asia via trans-Atlantic shipping in the 16th to 19th centuries.
Origin
The genus Aedes (Greek for “unpleasant”) is home to more than 950 species of mosquitoes, many of which are serious biting nuisances and vectors of disease. Aedes mosquitoes are the primary pathogens of several human viral diseases, including chikungunya fever, dengue fever, yellow fever and Zika virus.
Despite confined to their native temperate and tropical habitats, some Aedes mosquito species have spread beyond their native ranges, either as a result of introduced into new areas by humans or as a result of changing environmental influences. These mosquitoes, and the diseases they carry, have caused immense human suffering worldwide.
Aedes aegypti, also known as the yellow fever mosquito, was among the first mosquitoes to discovered and is one of the world’s oldest and most important vectors for human viruses. This mosquito was the primary vector of the virus that ravaged the Americas in the early twentieth century and continues to be a major player in the spread of chikungunya, dengue, and Zika fevers.
Female Aedes aegypti lay their eggs singly on moist surfaces close to the waterline, such as marshes, tree holes or plant axils. They may remain dormant in these sites for several days or weeks before hatching.
Once the eggs have hatched, they develop into larvae in the water for days or weeks before becoming pupae in the soil. After a period of growth, the adult Aedes aegypti emerges from its larval stage and takes flight.
During the early stages of its life cycle, Aedes aegypti found in wetlands, wooded and grassland areas where it can thrive near human populations. The mosquito prefers warm and humid conditions, but is tolerant of a wide range of climates.
Aedes aegypti has recently expanded its range into the western United States, reinvaded southern Europe and now has adapted to urban conditions in Australia. It is a major disease-carrying vector in these regions, and its re-emergence could place considerable pressure on public health systems across the world.
Aedes aegypti introduced into the Americas and into Europe in the early centuries of European settlement, most probably by ships sailing from Africa. It has adapted to the warmer climates of these areas and now is the leading disease-carrying mosquito in some of these regions.
Life cycle
The life cycle of Aedes aegypti is a complex process, involving four stages: egg, larva, pupa, and adult. This mosquito is a vector for diseases such as dengue fever, which transmitted worldwide.
Aedes aegypti eggs hatch into mosquito larvae, which feed on organic matter in water. This stage lasts for a day or two before a mosquito develops into a pupa and emerges into an adult. The lifespan of an Aedes aegypti depends on the temperature, food, and type of water.
Female Aedes aegypti lay eggs in a variety of places, including mud close to the water line, and in artificial or natural containers holding water. Such containers may include dishes under potted plants, bird baths, ornamental fountains, tin cans, and discarded tires (see figure 1).
Once the eggs laid, they can remain dormant in water for months or longer so long as there is enough water to sustain the larval stage. However, when the temperatures are hot, Aedes aegypti will begin to develop quickly and leave the container to find other sources of food.
Temperature has a great influence on the development of Aedes aegypti, as it affects the duration of the egg stage, larval and pupal stages, and the number of adult mosquitoes that will emerge from the water. Studies have found that the temperature of a container should be below 23 degC and above 29 degC to support the maximum development rate of Aedes aegypti.
As a result, the number of Aedes aegypti that can survive in a given temperature is determined by how much energy they have stored. When the temperature is high, Aedes aegypti are less likely to survive in the egg and larval stages; they will also have more difficulty surviving in the pupal and adult stages as the temperatures drop.
In addition, when the temperatures are low, Aedes aegypti can spend days without feeding or developing into a pupal case. This allows them to evade predators that would otherwise attack them.
Aedes aegypti have an average lifespan of about two weeks in the wild, but this may vary from location to location and season to season. In laboratory experiments, survival curves have use to study the effects of temperature, food, and water on the immature development, adult emergence, and reproduction of Aedes aegypti. These curves allow researchers to predict the development and survival rates of Aedes aegypti under different conditions, which could help them to develop effective management strategies.
Diseases
The Aedes mosquito is the primary vector for a number of viral diseases, including dengue fever, Zika, chikungunya and yellow fever. Infections with these viruses can be mild or severe, with the most serious symptoms requiring urgent medical attention.
Diseases spread by Aedes mosquitoes typically occur in tropical, subtropical and temperate regions around the world. Several Aedes species are able to transmit viruses, but the most important vectors are Aedes aegypti and Aedes albopictus.
Aedes aegypti is an invasive species that originated in Africa, where it first detected in the late 18th century (Nelson 1986). The mosquito has since spread worldwide and is now present in the Americas, Europe, Asia and Australia.
Adult Aedes mosquitoes distinguished from other types of mosquitoes by their narrow black bodies and unique patterns of light and dark scales on the abdomen and thorax. Females have alternating bands of light and dark on their legs, while males have a white “lyre” shape on the dorsal side of the thorax that they use to identify each other (Figure 4).
Both Aedes aegypti mosquitoes and Aedes albopictus mosquitoes are capable of carrying and spreading viruses that cause many illnesses, but Aedes aegypti has a higher capacity than Aedes albopictus for transmitting yellow fever. Aedes aegypti can also transmit other virus-related diseases, including tularemia and the parasitic nematode Brugia malayi.
Aedes aegypti, and Aedes albopictus, commonly found in the United States, with populations varying by region. However, Aedes aegypti populations are declining in parts of the country due to increased competition with Aedes albopictus, especially in urban areas.
The genus Aedes is made up of over 700 species. Approximately 50 of these species are known to be vectors of viruses and other pathogens. Although Aedes aegypti, Aedes albopictus and other Aedes species have the capacity to carry and spread many different viral infections, their ability to do so limited by a number of factors.
Some of these factors include climate, climatic conditions and the habitats in which they live. Vaccines may help to reduce the burden of some of these infections. Other interventions include vector control, environmental management and other strategies that reduce the ability of Aedes aegypti, or other Aedes species to spread viruses.
Prevention
Aedes mosquitoes can controlled through a variety of methods. These include environmental management, chemical control and genetic approaches (Figure 1).
Environmental management includes eliminating containers habitats where Aedes lays its eggs. These habitats found in stagnant water that can collect in places like old tires, buckets, trash cans and pet dishes. It’s important to empty and clean these sources of standing water at least once a week.
Another way to reduce Aedes populations is to use ovitraps. These are black, cylindrical containers filled with water that have a mesh top and paddles mounted on the side.
The female Aedes lays her eggs on the paddles, where they fall beneath the mesh and develop into larvae. The larvae grow and molt four times before they become pupae. The pupae, which live near the surface of the water, breathe through tubes on their backs.
When a pupa dies, the skin splits and the Aedes becomes an adult. These mosquitoes can bite people throughout the day and can transmit Zika virus, dengue fever, yellow fever and chikungunya.
Prevention for children is to keep them away from areas where mosquitoes breed, such as their school and backyards. Also, encourage them to wear protective clothing and mosquito repellents to help prevent bites.
Aedes mosquitoes can also controlled by using temephos, a larvicide that kills Aedes larvae when it comes into contact with water. It’s an EPA-registered insecticide that is safe for human and animal use, has a long shelf life and can use safely in water containers.
However, it’s important to read the label and reapply insect repellent as directed. During outdoor activities, it’s also important to wear long-sleeved shirts and pants so that mosquitoes won’t have access to bare skin.
Aedes mosquitoes are a major health concern for people of all ages in Europe. They can spread dengue, yellow fever and chikungunya, and have reported to re-colonize in some parts of the world. In some countries, eradication efforts have failed but they can control by reducing mosquito habitats and using other effective methods.
Recommended readings:
- A Genome-Wide Association Study of Sahiwal Cattle
- Dengue Fever Symptoms and Treatment Pakistan
- Malaria – Symptoms, Plasmodium, and Transmission of the Disease
- Best Foods For Dengue Treatment in Pakistan
