Be Careful Of Aedes Aegypti : Knowing Of The Signs, Symptoms And Preventing of Dengue Fever

A. AEDES AEGYPTI

The yellow fever mosquito ( Aedes Aegypti ) is a mosquito that can spread dengue fever, chikungunya, and yellow fever viruses, and other diseases.The mosquito can be recoqnized by white markings on its legs and a marking in the form of a lyre on the thorax.

The mosquito originated in Africa but is now found in tropical and subtropical regions throughout the world.Aedes Aegypti is a vector for transmitting several tropical fevers.Only the female bites for blood, which she needs to mature her eggs.To find a host , these mosquitoes are attracted to chemical compounds emitted by mammals.These compounds include ammonia, carbon dioxide, lactic acid, and octenol.

Scientists at Agricultural Reasearch Service have studied the specific chemical structure of octenol to bettet understand why this chemical attracts the mosquito to its host.They found the mosquito has preference for "right-handed" ( dextrorotatory) octenol molecules.

B. SIGNS AND SYMPTOMS OF DENGUE FEVER

Dengue fever, also known as " Breakbone Fever", is a mosquito-borne tropical disease caused by the dengue virus.The alternative name for dengue, " breakbone fever" , comes from the associated  muscle and joint pains.

Dengue is transmitted by several species of mosquito within the genus, Aedes, principally A.Aegypti.The virus has five different types ; infection with one type usually gives life long immunity to that type, but only short-term immunity to the others. Subsequent infection with a different type increases the risk of severe complications.Treatment of a cute dengue is supportive, using either oral or intravenous rehydration for mild or moderate disease, and intravenous fluids and blood transfusion for more severe cases.

Typically, people infected with dengue virus are signed as follow :

• Asymptomatic (80%) or have only mild symptoms such as an  uncomplicated fever.
• Others have more severe illness (5%) , and in a small proportion it is life-threatening.
• The incubation period ( time between exposure and on set of symptoms ) ranges from 3 to 14 days, but most often it is 4 to 7 days.
• Travelers returning from endemic area are unlikely to  have dengue if fever or other symptoms start more than 14 days after arriving home.
• Children often experience symptoms similar to those of the common cold and gastroenteritis (vomiting and diarrhea) and have a greater risk of severe complications.
• Initial symptoms are generally mild but include high fever.

The characteristic  symptoms of dengue are 

• Sudden-on set fever.
• Headache ( typically located behind the eyes ).
• Muscle.
• Joint pains.
• A rash ( similar to measles ).

The course of infection is divided into three phases :

I. The Febrile Phase involves 

• High fever, potentially over 40 C (104 F), and is associated with generalized pain.
• A headache; this usually lasts two to seven days.
• Nausea and vomiting may also occur.
• A rash occurs in 50 - 80% of those with symptoms in the first or second day if symptoms as flushed skin, or later in the course of illness ( 4 - 7 days ) as a measles-like rash.A rash described as " islands of white " in a sea of red " has also been observed.
• Some petechiae ( small red spots that do not disappear when the skin is pressed, which are caused by broken capillaries ) can appear at this point, as may some mild bleeding from the mucous membranes of the mouth and nose.
• The fever itself is clasically biphasic or saddleback in nature, breaking, and then returning for one or two days.

II. The Critical Phase

Picture : The rash of dengue fever in the acute stage of the infection blanches when pressed

The disease proceeds to a critical phase :

• Fever resolves.
• There is leakage of plasma from the blood vessels, typically lasting one to two days.
• Fluid accumulation in the chest and abdominal cavity as well as depletion of fluid from the circulation and decreased blood suply to vital organs.
• Organ dysfunction and severe bleeding, typically from the gastrointestinal tract.
• Shock ( dengue shock syndrome ) and hemorrhage ( dengue hemorrhagic fever ) occur in less than 5% of all cases of dengue.

Those who have previously been infected, with other serotypes of dengue virus ( "secondary infection ") are at an increased risk.This critical phase, while rare, occurs relatively more commonly in children and young adults.

III. The Recovery Phase

Picture : the rash commonly forms during recovery from dengue fever with its classic islands of white in a sea of red.

The recovery phase occurs :

• The resorption of the leaked fluid into the bloodstream that usually lasts two to three days.
• The improvement is often striking, and can be accompanied with severe itching and a slow heart rate.
• Another rash may occur with either a maculopapular or a vasculitic appearence, which is followed by peeling of the skin.
• A fluid overload state may occur ; if it affects the brain, it may cause a reduced level of conciousness or seizures.
• A feeling of fatigue may last for weeks in adults.

C. Preventing of Dengue Fever

There some ways to prevent dengue fever :

• Using Mosquito repellents that contain DEET  ( N, N-diethylmetatoluamide, 20 to 30% concentration, but not more ).
• Wearing long-sleeved clothing and long trousers when outdoors during the day and evening.
• Spray permethrin or DEET repellents on clothing, as mosquitoes may bite through thin clothing.
• Using mosquito netting over the bed if the bedroom is not air conditioned or screened and treating the mosquito netting with a insectiside permethrin.
• Fogging
• Spray permethrin or similar insectiside in the bedroom before retiring.
• Using the mosquito traps like the lethal ovitrap.