Learn more about the Aedes aegypti mosquito and how to take care of your health and the whole community.
How is the Aedes aegypti mosquito?
Despite their small size, mosquitoes are considered one of the most dangerous animals in the world due to their ability to spread diseases that can even lead to death.
It is estimated that there are approximately 3,000 species of mosquitoes worldwide. But calm down, not all mosquitoes bother humans or are capable of transmitting viruses.
Only females of some species – about 6% – need human blood to lay eggs. Of these, half are capable of being a vector of agents dangerous to humans. However, the effect of these pets is devastating on public health.
Among the species that cause a lot of concern is Aedes aegypti. An even smaller insect compared to common mosquitoes (less than 1 cm), with a body covered in white stripes on the trunk, head and legs and, since it flies preferentially during the day, it becomes more difficult to perceive its approach.
Some characteristics are very specific to Aedes, such as the tendency to fly at an average height of 1.5 meters above the ground and a preference for poking in the early morning and late afternoon.
Like other mosquitoes, male and female feed on substances rich in sugar, such as nectar and sap – carbohydrates extracted from plants -, but to generate and mature eggs, females need blood.
Their reproduction is accelerated, and they choose places of clean and still water to deposit their eggs. There are about 40 every 3 days.
Considering that the average life span of a mosquito is 30 days, the number of eggs can reach 400 per female.
Aedes behavior
There are some behaviors common to the Aedes mosquito, making circulation (and therefore bites) more frequent in some regions, times and temperatures. Understand:
Circulation area
Typical of urban areas, the Aedes is called the domestic mosquito because it circulates in the vicinity of houses, schools or places with a concentration of people, as the insect is well adapted to artificial breeding sites.
As cities and urban centers have more accumulation of containers, garbage or water deposits conducive to the laying of eggs, the mosquito finds an inviting environment.
The Aedes does not cover very long distances and, as it finds food and breeding conditions in urban centers, there is no tendency to go too far for rural areas.
Eating habits
Their habits are preferably diurnal, usually stinging in the early morning and late afternoon. But it is important to remember that it is also considered an opportunistic insect, that is, it can bite at night.
As they tend to circulate predominantly during the day, it becomes more difficult to perceive the approach of the insect, which has the noise of the flight softened by other sounds.
Optimal temperature
In general, it is the warmer temperatures that favor the circulation of the insect, so it is common to hear that air conditioning can help to combat it. As the place gets colder, there is a tendency to repel Aedes, but that does not kill it or guarantee safety to people.
Conditions for reproduction
The female prefers clean water (without much organic waste) and stops to lay eggs, but it is not a rule. Therefore, it is important to combat any accumulation of water.
In fact, it is the conditions of temperature and stability that weigh the most at this time. For this reason, Aedes looks for water deposits with less incidence of light (that is, darker), standing still and with higher temperatures.
Place that sting more
There is a preference for legs and feet, but Aedes does not make much distinction when there are exposed areas. In general, the lower limbs are the most attacked due to the mosquito flying low and being repelled by light.
The mosquito life cycle
Aedes basically have 3 very distinct phases: eggs, aquatic phase (larva and pupa) and adult phase.
The female looks for places with clean, still water to lay the eggs, depositing them a few millimeters above the surface. The mosquito embryo takes approximately 48 hours to develop and contact with water is enough for the egg to hatch.
Eggs that do not come into contact with water can survive for up to 450 days, waiting for favorable conditions.
When the water comes in contact with them, these eggs break quickly, beginning the development of the larva, which is the beginning of the aquatic phase – at high temperatures, around 30 ºC, between 7 and 10 days the insect is formed.
For this reason, rainy periods have higher levels of mosquito circulation, as soon as, often, a small amount of rain is enough for water containers and deposits to fill and Aedes begins to develop.
They grow until they reach the pupal stage, which is considered an intermediate stage of development. During this period, there is a decrease in the larvae movement (low mobility), indicating the passage to the final phase, that is, the adult phase.
The time of development of the insect depends a lot on the temperature. Warmer climates accelerate the process, making Aedes go through 3 stages and reach adulthood in about 7 days.
During development, there are predominant characteristics, which are:
- Eggs : they are clear, translucent and slightly whitish. Over time, they will acquire a darker color.
- Larva : they do not like bright environments, and dark places are quite conducive to the deposit of eggs, such as water tanks.
- Adult phase : the female is ready to lay eggs after approximately 3 days of feeding on blood (gonotrophic cycle), restarting the cycle.
How does the virus infect humans?
It is important to remember that males feed exclusively on fruits and it is only females that bite humans . As they need blood to lay eggs, they are responsible for the transmission of diseases .
Thus, a female mosquito bites the infected human being and acquires the virus, which invades the insect’s stomach cells and begins to multiply.
Each cell releases about 100 viral particles that invade its neighbors. Between 7 and 10 days later, Aedes’ stomach is full of the virus, which then reaches the circulatory system and affects the entire body of the insect, until it reaches the salivary glands.
At this stage, the mosquito is still not able to transmit the disease, because the viral amount in its saliva is still small. But it takes about 14 days for the virus load to rise to the point of being transmitted.
With the bite, at the same time that it sucks the blood, the insect’s saliva enters the site. There are two important substances involved in this process that start to act quickly: an anesthetic agent and an anticoagulant agent.
While the anesthetic factor cushions the area and prevents the person from feeling pain – acting as a defense mechanism against the mosquito itself – the anticoagulant factor works by ensuring that the blood reaches the Aedes’ stomach in an appropriate consistency.
This exchange of material – blood for saliva – is common to all bites, but if the mosquito is infected with dengue, zika or chikungunya virus, it is also through saliva that transmission occurs.
As soon as the virus particles penetrate the body, an infection process for reproduction begins. For that, they need to invade the cells and replicate.
If we go back to biology classes, we will remember that a virus is an element that needs a host to complete its life cycle. This means that it must infect other cells, alter its normal functioning and order replication of viral particles to occur.
That is, it is as if the cell became an infectious plant in the organism.
For this to occur, viruses have molecules on the surface (or outer layer) capable of attaching themselves to cell membranes. From this approach, the virus invades the cell and begins to modify cell function.
New virus particles are produced in the host and are released to the organism, infecting other cells and constituting the contamination cycle. But it does not stop there, because the infected Aedes puppies can also be born vectors of diseases – the result of vertical transmission. It is estimated that for every thousand mosquitoes of an infected mother, up to 19 have the virus.
Viruses and diseases transmitted by Aedes aegypti
The same mosquito is responsible for transmitting different viruses – it is estimated that there are more than 50 types. However, the most common and worrying are the causes of dengue, zika, chikungunya and yellow fever . Learn more about each one:
The dengue virus
The dengue virus is called DENV, and there are 4 circulating types in Brazil, DENV-1, DENV-2, DENV-3 and DENV-4. These types refer to small variations of the same type of virus.
After contracting the disease and recovering, the patient creates immunity to the type of virus that infected him. But as there are 4 variations of DENV, it is possible to be affected 3 more times, as long as the mosquito is contaminated with the other types of viruses.
In the face of the infectious agent, the immune system acts by trying to fight and retain viral spread. Thus, antibodies to the dengue virus are created, causing future infections to be combated through more specific immune responses.
However, it is important to remember that if the patient is infected with another type of dengue, the disease can take a more aggressive course and trigger a hemorrhagic dengue, for example.
Immune memory, which is very effective in preventing reinfection by the same subtype of DENV, may be responsible for the highest risks. The body recognizes the agent that is very similar to that of the past infection, and promotes an increase in the production of antibodies.
But the small difference in the dengue serotype means that there is an inefficient fight and, thus, the virus spreads through the body, usually causing more intense symptoms.
The Zika Virus
The Zika virus (ZIKV) is not a new agent, it was first reported in 1947 in Uganda.
At the time, the infectious was isolated from a monkey, but shortly thereafter, in 1954, the first human report occurred. Initially, ZIKV was characterized as a virus with sporadic occurrence (spaced), as there were few diagnosed cases.
However, in 2007 the first outbreak of the disease occurred in Yap Island, Federated States of Micronesia. Data show that more than 70% of the local population over 3 years old was infected.
Although there were not many complications and hospitalizations, the number was quite alarming.
From that year on, the concern with the Zika virus gained worldwide space. In 2015, the first cases of Zika in Brazil were reported and there was notification that the infection is related to Guillain-Barré Syndrome and microcephaly.
Studies are still recent and, therefore, the behavior of the ZIKV virus is still poorly understood. It is believed that after contact with the agent, the human organism creates immunity to future infections, however, the possibility of reinfections is not completely ruled out.
Transmission occurs predominantly by the bite of the Aedes mosquito contaminated with ZIKV. Even so, the World Health Organization (WHO) warns that there are reports of sexual transmission in some countries, and the use of condoms during sexual intercourse is essential.
When the virus reaches the human organism, in general, the symptoms tend to be mild and recovery does not involve major complications. Of the 17594 cases diagnosed in 2017, there was only 1 death due to the disease.
However, in addition to patients with immune disabilities, pregnant women deserve attention, as recent studies indicate that ZIKV can cross the placenta until the 3rd month of pregnancy, or find an access route through the amniotic pouch from the 2nd trimester.
When it reaches the baby, Zika is capable of causing microcephaly and other changes in the nervous system.
The chikungunya virus
The CHIKV virus was isolated for the first time in Tanzania, in 1952. In urban areas (that is, those that are not forests), the agent can be transmitted by two species of mosquito, Aedes aegypti and Aedes albopictus.
However, the Ministry of Health warns of the possibilities of vertical transmission (during delivery, the infected mother infects the baby) and by blood transfusion, even though these are less common forms.
One of the main and most intense symptoms of the disease is joint pain, causing the patient to contract. This curved and compressed posture was the reference for naming the infection, because “chikungunya” is a term derived from “makonde”, which means “those who bend”.
The yellow fever virus
In Brazil, yellow fever has already caused endemic concerns in the 1940s, and at the time, it was eradicated from the national territory, but it showed a significant increase in cases in 2017, reaching 777 infected by the month of August.
The disease lasts an average of 10 days and can trigger fever, headache , nausea, body aches, bleeding and jaundice (yellow skin and eyes), and the treatment consists of rest and symptom relief, usually requiring hospitalization of the patient.
Read more: Yellow fever vaccine: when and where to take, side effects
Other viruses
Although dengue, zika and chikungunya are the diseases most related to Aedes aegypti, they are not the only ones. The mosquito is a vector for other infectious agents capable of causing Mayaro Fever and West Nile Fever, for example.
Mayaro Fever, which has symptoms very similar to chikungunya, affected about 200 people in the North and Midwest regions.
According to the World Health Organization (WHO), West Nile Fever cases have been growing alarmingly in countries in southern Europe and central Europe. In early 2018, Brazil reported the first infection by the virus in horses, which triggered the alert about the disease.
Difference between dengue, zika and chikungunya
The 3 diseases are transmitted by the same vector, Aedes aegypti and, sometimes, can manifest similar symptoms. But a closer look at the patient’s condition is enough to notice that there are very striking differences, especially in the intensity of the symptoms.
The treatment of both consists mainly of rest and amelioration of the resulting symptoms, such as pain and malaise, and most of the conditions have a good recovery, as long as they are correctly diagnosed and monitored.
What are the symptoms?
The viruses transmitted by the Aedes mosquito have more than the vector in common, since the clinical signs they are capable of causing can be very similar, especially at the beginning of the infection.
Despite this, there are some points that differ and help in the characterization of each disease:
Dengue
High fever, usually above 38 ºC, lasting between 4 and 7 days, and headache, especially behind the eyes, are quite characteristic.
Skin patches may appear in up to half of patients and muscle pain is more common and severe compared to joint pain (which is usually mild when present).
It is estimated that for each symptomatic patient, approximately 3 other people were bitten and did not develop symptoms.
Zika
The patient infected with the Zika virus generally does not present feverish conditions or, when they occur, they are mild (below 38 ºC) and last for about 2 days.
But the spots are the most specific sign of the infection. They usually appear before fever, suddenly and affect more than 90% of patients, usually combined with severe itching.
Joint pain is usually mild or moderate and can cause swelling in the painful area. It is common for patients to develop episodes of conjunctivitis and enlarged lymph nodes.
On average, about 80% of people bitten by infected mosquitoes do not develop any symptoms.
Chikungunya
Patients usually present with high febrile states, above 38 ºC for 2 or 3 days, in addition to spots on the skin that itch a little until the 5th day after infection.
Muscle pain tends to be less than in dengue and zika, but the involvement of the joints is greater, representing severe pain and edema in the area.
The rate of infected people who develop symptoms is much higher in the case of CHIKV, with up to 95% of those infected being symptomatic.
In addition, up to 50% of patients will experience joint pain after recovery. They can be intense and extend for months or years.
Prevention: how to fight the mosquito?
The main way to fight diseases caused by Aedes aegypti is to eliminate mosquito outbreaks to reduce its circulation.
Control strategies mainly involve mechanical and chemical actions. Due to the biology of the mosquito, the aquatic phase is the most favorable to combat, as soon as the larvae and pupae are deposited in the containers and surfaces and do not spread until they become mosquitoes.
The mechanical control consists of identifying and eliminating the accumulated standing water, reducing the favorable locations for the deposit of eggs from the Aedes.
As for chemical control, it refers to the use of insecticides at home or through smokes (insecticide spray). However, it is necessary to remember that this is a minimization measure and the control should focus, above all, in the fight against egg deposits.
It is also worth remembering that insecticides only eliminate adult mosquitoes, which are already circulating.
At home
- Take care of the garden : avoid containers or places that can accumulate water, such as plant pots;
- Add sand to the pots : it absorbs water from irrigation and rain;
- Wash the containers of plants and animals : use a brush, water and soap to clean the pots;
- Take care of the garbage : do not accumulate pots, bottles or packaging and always dispose of correctly;
- Take care of the water tank : keep it hygienic and cover it properly;
- Clean the yard and the gutters : watch out for the accumulation of leaves, branches or dirt that could block the passage of water.
In addition, inside the home or in the home area it is necessary to keep an eye on places that often go unnoticed, such as:
- Water support and filters;
- Garbage baskets;
- Air conditioning trays;
- Drains and sanitary facilities;
- Marquees, awnings or roofs.
In the neighborhood
Observe the surroundings and participate effectively in the fight against Aedes. It is not enough to eliminate outbreaks in your home if there are others nearby. That is why the fight must be a community action:
- Observe manholes or holes in the street that can accumulate water;
- Notify the city hall in case of vacant lots or abandoned houses;
- Talk to neighbors about combat strategies;
- In cases of accumulated garbage or incorrect disposal of waste, notify the City.
How to eliminate outbreaks?
If you find larvae or outbreaks of Aedes, throw the standing water on the dry ground or on the ground and then wash the container with soap and water, giving the correct disposal or disposal. In places that cannot be removed, such as swimming pools, it is necessary to apply disinfectant cleaning products and notify the health agents who will apply the larvicides.
It is important to remember that bleach can be used to combat larvae, as long as the container to be sanitized is not used to store water for human consumption (such as water tanks). Bleach can be applied to:
- Toilet;
- Sanitary discharge boxes;
- Drains;
- Drums or vats that hold water for cleaning, for example.
How to protect yourself?
In addition to combating Aedes outbreaks, other measures can be taken to reduce the risk of mosquito bites. At home, you can:
- Put screens on the windows, preventing the insect from entering;
- Sleep or rest under mosquito nets;
- Have electric vaporizers around the house;
- Use environmental insecticides.
As for self-care measures, you can use repellents, as long as they are duly certified by ANVISA, and choose clothes that protect the body and reduce the exposed skin area, especially long pants and closed shoes – as soon as Aedes preferably bites the lower limbs .
Remembering that these are effective measures to protect and combat Aedes. Using homemade formulas (such as citronella or clove oil) are not scientifically recognized alternatives.
In addition, the World Health Organization draws attention to the possibility of the Zika virus being transmitted through sexual contact as well. Therefore, in addition to taking care to fight the mosquito and keep it away, it is necessary to use condoms in all sexual relations , reducing the risk of Zika and several other infectious diseases.
Aedes aegypti and pregnancy
Pregnancy calls for extra care in relation to the Aedes mosquito, so it is very important to do prenatal care and keep vaccinations up to date.
How to prevent the bite
To help prevent pregnancy, using repellents is recommended, always following medical recommendations, respecting the reapplication time and opting for products approved by ANVISA.
Read more: Repellent for pregnant women (icaridine, DEET), brands, which is the best?
There are risks of contracting the Zika virus through sexual intercourse, so maintaining the use of condoms is essential. In addition, it is important to prepare environments with screens and mosquito nets, reducing the risk of being bitten and, if possible, avoiding risk areas.
Care must be taken throughout pregnancy, but it is mainly in the first trimester that there are greater risks to the mother and baby, especially in relation to spontaneous abortion and microcephaly (due to Zika infection).
It is important to emphasize that medications should not be taken without medical advice and that all symptoms should be reported to healthcare professionals.
Care also extends to after delivery, paying attention to the protection of the baby through physical barriers (clothing and mosquito nets).
Consultations with the pediatrician are essential and all signs or behavioral changes should be taken to the doctor, especially if there is fever, skin spots and redness in the eyes.
Infected mothers
In the case of mothers who have been bitten by the infected Aedes, the Ministry of Health indicates that breastfeeding should be continued normally until 2 years of age or older, as there is no evidence that the virus can be transmitted during breastfeeding.
For pregnant women infected with Zika, there is greater concern in relation to microcephaly. In such cases, it is essential that the child is assisted from birth, through specialized programs. Stimulation and early monitoring reduces the impact of the malformation and aids in the child’s motor, neurological and cognitive development.
History of Aedes aegypti
The Oswaldo Cruz Institute indicates that the first scientific report of Aedes was in 1762. At the time, the mosquito was named Culex aegypti, but in 1818 there was a description of the genus Aedes and, when classified in this group, it was renamed Aedes aegypti .
Originating in Egypt, in Africa, it is not today that the species circulates in national territory, because at the end of the 19th century the small insect was already a matter of concern in Curitiba (PR) and, shortly afterwards, in Niterói (RJ).
Brought by slave ships at that time, it was the transmission of yellow fever that put the population at risk.
In 1955, with vector eradication measures, chemical insecticides were sprayed and eliminated Aedes. But it didn’t take long for him to return to Brazilian soil.
It was between the 1960s and 1980s that the mosquito reappeared, brought mainly from Singapore, in Southeast Asia. Spreading throughout the territory, today it is difficult to think about eradication.
From the beginning of 2018 until the month of August, together, dengue, zika and chikungunya add up to almost 269,500 cases in Brazil.
Although there is a total reduction of approximately 40% compared to the same period in 2017, the 3 infections still have a high rate of transmission. Ways to prevent them come up against the difficulty in eliminating mosquito outbreaks and the easy spread of viruses.
Caring for the environment and information are the best methods to reduce risks and combat Aedes. Take care of your health and find out in the Healthy Minute!
