Mosqitoes

Do you know everything about mosqitoes? Everyone knows that mosqitoes suck blood and spread dengue fever. But why do they suck blood? What kind of diseases do they also spread? What is the mosquitoes'life cycle? Well, I've done a little reasearch of my own and found out quite a bit of knowledge! Here is what I've found!

Mosqitoes belong to a family of flies that are called Culicidae and are small fragile insects that have six delicate legs and two wings covered in scales. The head of a mosquito is equipped with a projecting proboscis which conceals and protects the long piercing and sucking mouthparts. These biting insects have a complex life cycle; the immature stage is totally aquatic and the adult is terrestrial. The adult female returns to a water habitat for a brief period to lay each batch of eggs. Mosquito species vary in their breeding habits, biting behaviour, host preferences and flight range. Most mosquitoes disperse less than two kilometres; some move only a few metres away from their original breeding place, others can fly some 5 or 10 kilometres, and a few species will disperse up to 50 kilometres downwind from the larval habitats.

On average, a female mosquito will live 2-3 weeks, but the male's lifespan is shorter. Within their lifetime both adult male and female will feed on nectar and plant fluids, but it is only the female that will seek a blood meal. So this is whymosquitoes suck blood! The majority of species require this blood meal as a protein source for egg development. Female mosquitoes are attracted to a potential host through a combination of different stimuli that emanate from the host. The stimuli can include carbon dioxide, body odours, air movement or heat. Upon locating a suitable host, the female will probe the skin for a blood capillary then inject a small amount of saliva containing chemicals which prevent the host's blood from clotting. This is often the pathway for potential pathogens such as viruses to enter a host. After engorging on the host's blood the female will find a resting place to digest her meal and develop eggs before flying off to deposit them in a suitable aquatic habitat.

The young larvae are called wrigglers and when they hatch, they will feed continuously and grow though four instars or moultsarval development is dependent on the availability of food and prevailing conditions, particularly temperature, but generally takes at least one to two weeks. The final larval instar develops into an active comma-shaped pupa from which the adult mosquito emerges about 2 days later to feed, mate and develop eggs for the next generation.

Now that we've covered the life cycle and why do they suck blood, let's move on to the diseases. Some of the diseases are the well known dengue fever, Australian encephalitis, Ross River virus disease and Barmah Forerst disease. Dengue is the most important viral disease transmitted by mosquitoes afflicting humans in a world context. Clinical symptoms range from mild fevers, to a severe and potentially life threatening haemorrhagic disease. In Australia, Dengue fever is restricted to Quensland where the major vector Aedes aegypti occurs. "Australian encephalitis" (AE), or "Murray Valley encephalitis" are synonyms for a clinical syndrome caused by infection with Murray Valley encephalitis virus or Kunjin virus. Symptoms are variable, from mild to severe with permanent impaired neurological functions, to sometimes fatal. Cases of AE occurs poradically in northern Australia and especially in the northwest of WA, but there have been no cases of MVE recorded in southeastern Australia since 1974. Ross River (RR) and Barmah Forest (BF) disease have been collectively known as "Epidemic Polyarthritis", however the two diseases have a slightly different clinical picture. A wide variety of symptoms may occur from rashes with fevers, to arthritis that can last from months to years with RR virus infection. RR disease is the most commonly reported mosquito transmitted disease to humans (over 6,500 cases in 1997) and occurs in all states of Australia. There are occassional local epidemics with hundreds to thousands of infections, with many going unreported. BF disease occurs in most states of Australia, although the annual number of cases are around 1/10th that of RR disease. A series of outbreaks during the early 1990's has highlighted the increasing importance of BF disease. Malaria in Australia has been endemic, but was declared eradicated from the country in 1981. However, approximately 700-800 cases are imported annually from travellers infected elsewhere.
This is all the information I've gained so far. If you have any information about mosquitoes, please send it to chia.joel@yahoo.com see you soon!