MOSQUITOES AND MALARIA

MALARIA AND MOSQUITOES

Malaria is a serious infectives diseases spread by some certain type of mosquitoes.It is most common in tropical climates countries such as Nigeria, India and Honduras. It is characterized by recurrent symptoms of chill, fever, and enlarged spleen. The disease can be treated with medication, but it often recurs.
Malaria is

endemic.(occurs frequently in a particular locality) in many third world countries.

Scientists researched that malaria kills an estimated 1million people each year worldwide.

Symptoms of malaria include fever headache and vomiting, and usualy appear between 10 and 15 days after the vector’s bite. If not treated, malaria can quickly become life-threatening by disrupting the blood flow to vital organs.In so many parts of the world, the malaria parasites have developed resistance to number of medicines prescribed for the cure of malaria.

MOSQUITOES

   Mosuquitoes are vectors of malaria parasites there are more than 3,000 species of mosquitoes in the world but there are three major types of mosquitioes.

Ø Aedees

Ø Anopheles

Ø  Culex

AEDES

There are sometime called “food water” mosquitoes because flooding is important for their eggs to hatch.

Aedes mosquitoes have admomens with poited tips.They include such species as the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus).The are strong fliers, capable of travelling great distances (up to 35 miles/121 km) from their breeding sites.They persistently bite mammals (especially humans), mainly at down and in the eary evening.Their bites are painful.

                                   ANOPHELES

   These tend to breed in bodies of permanent fresh water. Anopheles mosquitoes also have abdomens with pointed tips. They include several species, such as the common malaria mosquito (Anopheles quadri maculatus) that can sprad malaria to humans.

CULEX

   There tend to breed in quiet standing water.Culex mosquites have abdomens with burnt tips. They include several species such as the northern house mosquito (Culex pipiens). They are weak fliers and tend to live for only a few weeks during the summer months they persistently bite (prefenring birds over humans) and attack at down or after duck.Their bite is painful

LIFE CYCLE AND BREEDING OF MOSQUITOES

Mosquitoes like all insects hatch from eggs and go through several stages in their life cycle before becoming adults.The females lay their eggs in water when ,and the larva and pupa stages live entirely in water when the pupa changes into adults, the leave the water and become free-flying land insects.The life cycle of a mosquito can vary from one to several weeks depending upon the species.The adult ,mated female of some species can survives the winter in cool, damp places until springs,when they will lay their eggs and dies.Malaria is transmitted among humans by female mosquitoes of the genus Anopheles female mosquitoes take  blood meals to the carry out egg production,and such blood meals are the link between the human and the mosquito hosts in the parasite lifecycle.The Anopheles survives long enough to allow the parasite to complete its cycle on the mosquito host which last up to 10 to18 days.

GENRAL INFORMATION ABOUT MALARIA

There are approximately 3,500 species of mosquitoes grouped into 4 general.Human malaria is transmitted only by females of the genus Anopheles of the approximately 430 Anopheles species, only 30-40 transmit malaria (i.e are “vectors”) in nature.

   Anopheleses are found worldwide except Antarctia malaria is transmitted by different Anopheles species, depending on the region and the enveroment.

   Anopheleses that can transmit malaria are found not only has been eliminated. The latter areas are thus constantly at risk of re-introduction of the disease.

LIFE STAGE OF ANOPHELINE MOSQUITOE
Like all mosquitoes anopheles go through four stages. In their life cycle: egg-larva-pupa and adult. The first three stages are aquatic and last 5-14days, depending on the species and the ambient temperature. The adult stage is when the female Anopheles mosquito acts as malaria vector. The adult females can live up to a month (or more in capacity).But most probably does not live more than 1-2weeks in nature.

                                       EGGS

Adult females lay 50-200 eggs per oven position. Eggs are laid single directly on water and are unique in having floats on                                                      3days, although hatching may take up to 2-3weeks in colder climates.

                                  LARVAE

Mosquito larvae have a well-developed head with mouth brushes used for feeding, a large thorax, and a segmental abdomen. They have no legs. In contrast to other mosquitoes, anopheles larvae lack a respiratory spiphon and for this reason position themselves   so that their body is parallel to the surface of the water

  Larvae breathe through spiracles located on the 8^th abdominal segment and therefore must come to the surface frequently. The larvae spend most of their time feeding on algae, bacteria, and other microorganism in the surface micro layer. They dive below the surface only when disturbed. Larvae swim either by jerky movements of the entire body or through propulsion with the mouth brushes.

    Larvae develop through four stages or in stars after which they metamorphose into pupae at the end of each in star the larvone molt shedding their exoskeleton, or skin to allow for further growth

  The larvae occur in a wide range of habitats but most species prefer clean, unpolluted water. Larvae of anopheles mosquitoes have been found in fresh or salt water marshes, mangrove, swamps, rice fields, and grassy ditches, the edges of streams and rivers, and small temporary rain pools. Many species prefer habitats with vegetation. Other prefers habitats that have none. Some breed in open, sun-lit pools while other are found only in shaded breeding sites in forests. A few species breed in tree holes or the leaf axis of some plants.                                                                   PUPAE                                                                         The pupa is comma-shaped when viewed from the side. The head and thorax are merged in to a cephalothorax with the abdomen curving around underneath. As with the larvae, pupae must come to the surface frequently to breathe, which they do through a pair of respiratory trumpets on the cephalothorax. After a few days as a pupa, the dorsal surface of the cephalothorax splits and the adult mosquito emerges. The duration from egg to adult varies considerably among species and is strongly influenced by ambient temperature. Mosquitoes can develop from egg to adult in as little as 5 days but usualy take 10-14days in tropical condition                                                                                                          ADULTS                                                                                                                  

Like all mosquitoes, adult anopheles have slender bodies with 3 sections head thorax and abdomen.                                                                The head is specialized for acquiring sensory information and for feeding. The head is contains the eyes and a pair of long, many segmented antenna. The antennae are important for detecting host odors as well as odors of breeding sites where females lay eggs. The head also has an elongate, forward          , projecting proboscis used for feeding, and two sensory pulps.               The thorax is specialized for locomotion. Three pairs of legs and a pair of wings are attached to the thorax.                                            The abdomen is specialized for food digestion and egg development. This segmented body part expands considerably when a female takes a blood meal. The blood is digested over time serving as a source of protein for the production of eggs, which gradually fill abdomen. Anopheles mosquitoes can be distinguished from other mosquitoes by the palps, which are as long as the proboscis, and by the presence of discrete blocks of black and white scales on the wings. Adult anopheles can also be identified by their typical resting position .males and females rest with their abdomens stocking up in the air rather than parallel to the surface on which they are resting              Adult mosquitos’ usualy mates within a few days after emerging from the pulpal stage. In most species, the males from large swarms, usualy around dusk, and the females fly in to swarms to mate.                                                                                                                Males live for about a week, feeding on nectar and other sources of sugar. Females will also feed on sugar sources for energy but usualy require a blood meal for the development of eggs. After obtaining a full blood meal, the female will rest for a few days while the blood is digested and eggs are developed. This process depends on the temperature but usually take 2-3days in tropical conditions. Once the eggs are fully developed, the female lays them and resumes host seeking.             The cycle repeats itself, until the female dies. Female anopheles mosquito survives up to a month (or longer in capacity) but most probably do not live longer than 1-2weeks in nature. Their chances of survival depend on temperature and humidity, but also their ability to successfully obtain a blood meal while avoiding host defenses.                                                           THE BIOLOGY OF PLASMODIUM

Plasmodium is the parasite that responsible for human malaria, is among the most researched genera of parasites in the plasmodium falciparum is a protozoan parasite, one of species of plasmodium that cause malaria in humans .It is transmitted by the female Anopheleses mosquito. Malaria caused by this species (also called malignant or falciparum malaria is the most dangerous form of malaria with the highest rates of an estimated 247 million human malaria infections much more prevalent in sub Saharan African than in many other regions of the world, in most African countries over 75% of cases of malaria were due to plasmodium falciparum, whereas in most other countries with malaria transmission, other less virulent plasmodia species predominate. Almost every malarial death is caused by plasmodium.                                           There are three recognized forms of the Malaria disease, named according to the period which elapses between the recurrent attacks of fever. Each of these kinds is caused by a separate species of plasmodium; 1.tertian malaria, caused by plasmodium vivax , the fever recurring every forty-eight hours.2. Quatrain fever, in which the period between the fever attacks is seventy two hours and the causative parasite, is plasmodium malaria 3.Tropical fever or pernicious malarial. Where in the fever occurs at irregular intervals. It is caused by plasmodium falciparum .The life-cycle of the malaria parasite may be divided to two sections. The first part is spent in the blood of man. The rest of the cycle may be completed in several species of mosquito.                                                                                                                                                                                                                         THE LIFECYLE OF THE MALARIA PARASITE (PLASMODIUM)                                                       IN MAN

When the human subject is bitten by a Malaria-carrying mosquito sporozite are injected in to the blood stream along with the saliva from the insect. Each sporozite is a narrow spindle-shaped body with a central nucleus. The human subject develops no symptoms for ten day. All sporozite are found to have disappeared from the blood stream after about half an hour from the time of injection. They have reached the liver, where they invade the cells and undergo rapid division (schizogomy) so that a sporozite produces about one thousand. Small cells called merozoites. This cycle is the pre-erythrocyte phase i.e before invading the blood corpuscles (erythrocytes).During this phases the parasites is immune to quinine, mepacrine or any natural immunity of the host. The multiplication phase may continue repeatedly in the liver while merozoites are being released in the blood.                                                      Each merozoite attacks a red blood corpuscle, in which it becomes amoeboid growing at the expense of the corpuscle. This growing amoeboid stage is termed the trophozoite phase. Each trophozoite may accumulate fluid within its body, giving rise to the typical sintering shape.                                                                     The full grown trophozoite next becomes a schizent i.e cell which reproduces by schizogomy or splitting. Each schizent splits in to several (eight to twelve) Small nucleated masses known as merozoites, which burst the blood corpuscle and lie free in the blood plasma. During the trophozoite stage, the granules of waste material melanin and toxin collected in the cell and at schizogomy, they are released in to blood stream. It may be action of this melanin upon the body of the host which caused fever.                                                                                                                   Each merozoites attacks a fresh blood corpuscle, becomes a trophozoite and then a schizent. So producing more merozoites .This process of schizogomy recurs indefinitely. Every time the schizent split the toxic melanin is set free, causing the fever, this recurs at intervals, corresponding with the time taken for the completion the schizogomy cycle. Eventually, certain of the merozoites which enter fresh blood corpuscles behave differently from those which form schizent. At the end of their tropic phase they do not divide, but become free from the corpuscles and float in the blood stream. These individuals are known as gamonts or gametocytes i.e cells which will eventually produce gametes. Two distinct types of gamonts can be discerned (a) Female gamonts or macro gametocytes. (b) Male gamonts or micro gametocytes. Further development of the gamonts does not take place within the human body. This development takes place normally within the human body. This development takes place normally within the mosquito i.e a cold-blooded animal.                                            THE LIFE CYCLE OF THE MALARIAL PARASITE (PLASMODIUM) IN MOSQUITO  

When a mosquito draws in the blood of a malaria patient, include in the meal, drawn are gamonts, trophozoite, and merozoites if the mosquito is one of the Culex types, then all material drawn in to its stomach is digested. If, however, the insect is an anopheles mosquito then the reproduction of temperature stimulates the gamonts, while all other stages of the parasite are digested along with the blood corpuscles.                          After the maturation of gametes a lot of biological processes occurred in the mosquito, then the sporozite are enclosed in a cyst reach the salivary glands of the mosquito through the blood stream. These sporozoites are infected mosquito bites. Thus the life-cycle of the parasite is completed.                                 

TIPS ON HOW TO PREVENT MOSQUITO BITES OR MALARIA DISEASE.

TO prevent mosquito bites, follow these guideline:

1.   Stay inside when it is dark outside, preferably in a screened or air- conditioned room.

2.   Wear protective clothing (long-sleeved shrits)

3.   Use insect repellent with DEET(NN, die thylmetatolvamide). The repellent is availably in varying streng ths up to 100%.In young children, use a preparation containing less than 24% strength, because too much of the chemical can be absorbed through the skin.

4.   Use bed nets (mosquito netting) sprayed with or soaked in an insecticide such as permethrin or deltamathethrin.

5.   Use flying –insect sprayed indoor around sleeping areas.

6.   Avoid area where malaria and mosquitoes are present if you are at higher risk (for example, if you are pregnant, very young or very old).                                       Other steps that may be helpful in reducing the risk of malaria include using air conditioning and electronic fans, wearing protective clothing, using aerosol insecticides in your house, and taking  certain ant malarial medicines.                                                                           NOTE: The selection of medicines to prevent malarial depends on the geographical region where you may be exposed to malaria and your health condition.(such as being pregnant, being elderly or young, being sick, or having immunity or resistance to malarial ,or having allergies or sensitivity to the medicine. So visiting a nearby health center or hospital to see a specialized doctor for advice and treatment.  

Mr Shittu Quadri Babatunde