THE VAMPIRES OF THE TROPICS : An exhaustive overview

Communication process is said to be complete only when the receiver is able to decode and comprehend the conveyed message.

Due to the complexities in science at times , I try as much as possible to make my article easily comprehensible to the reader, this will facilitate easy asssimilation of the subject matter.

In the context of this article, Vampires of the tropic is referring to mosquitoes because of their natural and habitual nature of sucking and obtaining blood meal from their host, especially the humans in the tropics.

This article aims to fully and comprehensively explain in detail all about mosquitoes, their medical importance, life cycle, how they can transmit the pathogenic organism -plasmodium which causes malaria, their prevention and finally modern approaches to treatment of malaria. It is intended to reach out to both science and non science oriented individuals and I hope to achieve my goal of keeping steemit community apprised of trends in medicals field. More emphasis will laid on the female anopheles mosquito, the chief and most deadly vampire.

The mosquitoes

Those of Medical importance belong to the sub family Culicinae which is further divided into three tribes - Anophelini, Culicini (Aedes, Culex and Mansonia ) and Megarhini (the giant mosquitoes).

life cycle

They are small slender bodily flies with proboscis (a forward projecting structure for obtaining blood meal). They have different sexes, the males suck nectars of flowers and do not pose any threat to humans, they hardly live for more than a week and their main role is to fertilize the females. they die after fertilizing the female mosquitoes while the female ones especially the female anopheles sucks blood from humans because they need this blood for the maturation of their fertilized egg, though man is not the only source of blood meal. These females remain quiescent for about 2-3 days when they are fully fed for the maturation of their ovary, they remain indoors where they get their blood meal from humans, while the outdoor they rest in sheltered places like under surface of leaf, caves, or cans.

One amazing thing about these females ones is that they die soon after they have laid all the matured eggs provided their is adequate blood meal and breeding places.

After the eggs are laid (usually in hundreds) they may hatch within 24hours depending on the availability of water. That is to say that, the eggs need water to hatch. This explains why during rainy season, you tend to have numerous mosquitoes flying around. If water is not available, these eggs can remain unhatched for weeks or months.

Once the eggs are hatched, the larva are released, these larvae have a stiff hairs and breathing trumpet-like siphon which they use to pierce the surface film of water for gaseous exchange and being aquatic wrigglers ( they are mostly found in water where they breath and feed on microscopic organism ) they undergo further development into the pupa stage which resembles a lobster and finally transforms into the adults.

These final transformation can take 2days to a week depending on the temperature and they can suck blood within twenty four hours after maturation into adult.

How mosquitoes are attracted to humans

There are some questions that really need answers :

How do these mosquitoes detect humans?

What makes or keeps the blood fluidic in the mosquito and prevents it from clotting?

Can mosquitoes transmit HIV virus?

How do they know we are humans even at night, our location and site to bite so as to obtain blood?

Even as a child while growing up, I kept asking myself the same questions above. These mosquitoes can even go as far as locating that uncovered portion of your body to suck blood, I guess they in dare need of our blood for a purpose, read on and you will find out why.

Mosquitoes mostly bite during the night and are usually active between the late hours of the day from 6:30pm to early morning, 7am and are able to detect and suck blood from humans basically because of four reasons

• Through smell. Just as goats, sheep's and other animals have their unique smell, humans do as well. These unique smell of humans attract them a lot and it explains why when you rub mosquito Repellent creams such as Odomos they do not come near you one bit. Even when with the use of mosquito coil repellent they also do not in any way come close to you.

• Second mechanism is through the gas (carbon dioxide) we release, they have antennae which they use to detect carbon dioxide . As humans we naturally breath out carbon dioxide in exchange for oxygen. These gas attract these mosquitoes a lot to us.

• The third way through which they are attracted to humans is through body heat. Human body naturally is maintained at a temperature range of about 35-37 degree Celsius. These temperature is warm enough to attract mosquitoes and this also explains why during cold nights we tend to be untouchable by these vampires.

• They have antennae that can even detect lactic acid on our skin, a byproduct of muscular exertion. Some also detect humans through body movement and moisture.

A mosquito can "smell" its human blood dinner from a distance of up to 50 kilometres (30 miles) away. Source

To answer the question as regards whether a mosquito can transmit the virus HIV, the answer is an emphatic NO, this is because the virus cannot survive in the mosquito. Source

How they bite and suck blood

I would really say at this juncture that these little creatures deserve some credit, they have the ability to penetrate the skin of their host, as little as they are they can easily penetrate the skin and suck blood.
When they land on the human body, they have some sort of chemical receptors they use to locate a likely site suitable for sucking, they achieve this through detection of lactic acid on the skin as explained initialy above.
They also have mechanoreceptors that push so gently against the skin to detect differences in resistance that indicate arterioles and venules in certain spots. Source

Once they locate the perfect spot, they then use their proboscis to secrete saliva on human skin, this saliva contains an anticoagulant (prevents the blood from coagulating or clotting), some vasodilators that keeps the vein dilated so that blood keeps flowing to the region or spot where they are actively obtaining blood. The saliva also contains a chemical that acts like an anaesthetic to make you unaware of its bite most times.

why you have itching and inflammation at the site of bite.

If it’s your first mosquito bite ever, nothing will happen. You get one bite, free. Our immune system has not yet developed antibodies to recognize and flag the foreign chemicals. But after just one dose of mosquito spit, the familiar itchy bump left behind by subsequent bites is caused by an allergic reaction to all those chemicals the mosquito are squirting into you. The immune system releases histamines, chemicals that make the cells in the lining of our blood vessels to spread apart. This lets fluid leak out into the skin and it contains some components of our immune system that attack and destroy the foreign chemicals from the mosquito. The extra fluid from the leaking blood vessels causes a bump, which irritates other receptors in the skin, leading to the itching. Source

Medical importance

Malaria is the most important human disease transmitted by mosquitoes. The female anopheles mosquitoes are the sole vector of malaria parasite (plasmodium). The culex mosquitoes transmit Helmith infection notably bancroftian filariasis and also Malayian filariasis.
The aedes, for example Aedes aegypti, the important carrier of the virus responsible for yellow fever, has white bands on its legs and spots on its abdomen and thorax, it also causes dengue fever and zika fever

while the Mansonia transmit Wuchereria bancrofti - a filarial worm ( this leads to elephantiasis , a disease condition caused by the blockage of the lymphatic vessels of the body by these filaria worms ).
Mosquito bite causes discomfort, pain, delayed hypersensitivity reaction and insomnia (difficulty in sleeping) which is usually due to the annoying humming sound made by them. The frequency of the humming can be used to also differentiate between the male and the female mosquitoes.

control of these vampires

A lot has been said and written about these deadly vampires and their control is of utmost importance. Mosquitoes generally can be controlled through the following ways:

• personal protection (wearing of protective clothing, sleeping under insecticidetreated nets, use of repellents etc

• Destruction of the adult by the use of insecticides (this has to be used with caution to prevent poisoning) or even with the use of physical attack like killing them with your hand or a broom.

• Elimination of their breathing places, this is the most effective way of getting rid of them.

• Destruction of the larvae by introducing their biological or natural enemy - the Gambuzi or mosquito fish. This will eat up all the mosquito larvae in the pond, you tend to lose nothing here because what you have just done is to actually give free food to this Gambezi fish.

• Pouring of used engine oil over a stagnant water is also another way as this will suffocate the larvae to death by preventing them from breathing. So if you have any stagnant water around your neighborhood and you feel it is impossible to really clear the water, you can as well do this.

Now that a good foundation about mosquitoes have been laid, the concluding aspect of this article will now explain how and why mosquitoes are really deadly and responsible for the high mortality rates in the tropics. It will also take into consideration the latest findings as regards the treatment of malaria, vaccination and development of genetically modified malaria by oxitec. All this will be in the next article.

References and further reading

click Britannica

click the register

click NBCNEWS

Medical parasitilogy 4th edition by D.R. Arora and Brij Bala Arora (page73)

District Laboratory practice in Tropical Countries 2nd edition update part 2 by Monica Cheesbrough (page 239-258)

Kindly follow @cyprianj for more fascinating articles on medical field, nature and science.

I believe we learn everyday, I would love questions and constructive criticism if any. Suggestions and advise will also be highly appreciated.
thanks for reading

Appreciation

I sincerely wish to thank this wonderful mentor @greenrun, who has been of immense help. Thanks so much for your time and willingness to respond aptly to my questions. Your help was immeasurable. I also want to thank @rok-sivante you have been a motivator.
God bless you.