Dengue, a viral disease transmitted by mosquitoes, causes about 50 to 100 million infections per year worldwide. According to the statistics by the National Vector Borne Disease Control Programme, India has recorded over 33, 964 cases of dengue in 2017 so far.
"Dengue is transmitted by a mosquito called Aedesaegypti. Only the female Aedes mosquito bites humans. Over the years, this mosquito has adapted to its surroundings and flourished around humans taking maximum advantage of factors such as poor sanitation practices, improper solid-waste disposal, unsafe water storage practices, and poor pool management. Even a single bite by an infected mosquito can cause dengue," says Dr Swati R Hawaldar, Senior Manager (Health Education).
The disease takes on an epidemic form almost every year and creates panic among the public. Dengue is preventable and prevention is the first step in its management. Here is a lowdown on some characteristics of the dengue mosquito which make it difficult to control them.
No fuss breeding
The female dengue mosquito can lay eggs in any container which can hold some water. It can also lay eggs in the germ-ridden water of septic and toilet tanks. Hence, it is important to not let water stagnate anywhere and keep the surroundings clean. One should also make sure to close all containers that have water stored in them, scrub clean and turn over all containers like buckets/pans that have no lid. Disposable containers, bottles, food trays, used tyres must be disposed of in covered trash bins. We also need to regularly inspect, drain and clean water coolers, pans under refrigerators and ACs. It is advisable to observe a dry day once a week.
The dengue mosquito prefers to rest indoors as this protects them from climatic changes thereby increasing their life span. Thus, it is not enough to carry out fogging for mosquito control outside the house. People often shut their doors and windows to prevent the insecticide fog from entering their house and do not allow indoor spraying, which helps the mosquitoes survive.
Aedesaegypti lays eggs on the sides of containers and these remain stuck to the surface like glue. The eggs can survive without water for almost a year and hatch as soon as they are submerged in water. The larvae that emerge from the eggs are also tough and can survive in water for a long time even if the temperature is unfavourable. This makes it more important to avoid water stagnation in any form.
Aggressive day time bite
Unlike malaria mosquitoes, dengue mosquitos bite during the day with their activity peaking at dawn and dusk. It is preferable to have all day protection. At home, you can try using natural mosquito repellents like citronella oil, lemon grass oil and neem oil or chemical repellents to keep mosquitoes away. Cover your exposed areas well. If you need to go out, make sure to wear full-sleeved clothing and apply a mosquito repellant cream. Insecticide treated bed nets which are used extensively in malaria control are not very effective in preventing dengue.
Stealth attacker and sip-feeder
The female mosquito bites from the back to avoid easy spotting. It bites on the elbows and ankles. The female dengue mosquito never sucks a stomach-full of blood at one go but darts from one person to another takes just a sip, till the dengue virus spreads to several people. After every meal, she lays a batch of 400 to 500 eggs, which happens about 5 times in her lifespan.The mosquito lays the eggs in a different place every time.
Increase in incidence
Though the Aedes mosquito flies around and stays in a range of about 400 meters, international travel and trade has spread its activity and incidence across continents.Some studies also suggest that global warming and change in rainfall patterns have resulted in an increase of mosquito borne diseases like dengue and malaria in temperate climates.
Do we stand a chance against this canny mosquito
New and novel methods to combat dengue are being researched upon every day. Some examples include vaccines, the release of sterile male mosquitoes, and a promising method which involves infecting the mosquito with a harmless natural bacterium called Wolbachia. This bacterium blocks the dengue virus from growing in the mosquito's body. The government cannot employ enough persons to search every backyard to identify and destroy breeding sites on a consistent basis to prevent this mosquito from breeding. Therefore, as individuals and communities, we need to continue to put in all-out efforts to control this mosquito.