MalariadiseaseBiologyof mosquitoes as the vector for the malaria parasiteThey are two wingedflying insects that suck blood from humans and animals. Mosquitoes have aslender body, long legs and long needle-shaped piercing mouthparts. The wingsof anopheles mosquitoes are spotted and the adults measure between 2mm to12.5mm in length.
Life cycle ofmosquitoesMosquitoes have fourdistinct stages in their lifecycle and they include egg, larva, pupa and theadult mosquito. The females only bite once but they produce eggsbat intervalsthroughout their life. In order to be able to produce the eggs the femalemosquitoes require a blood meal and the digestion and developments of eggstakes2-3days. The females then search for suitable places to deposit their eggsafter which another blood meal is taken and another batch of eggs is laid. Theprocess is repeated until the mosquito dies. The female mosquitoes lay between30 and 300 eggs at a time.
The female anopheles mosquitoes lay their eggsdirectly on the surface of water, singly and they contain floats. The larvalperiod lasts between 4 to 7 days after which the fully grown larva changes intoa comma-shaped pupa which does not feed and spends most of its time under thewater surface. When mature, the pupal skin splits at one end and a fullydeveloped adult mosquito emerges.Species of malariaparasiteMalaria is caused byprotozoan parasites of the genus plasmodium vectored by the female anophelesmosquito. There are four species of malaria parasite which infect han beingswhich are;Plasmodium falciparumThis species causestropical malaria which occurs throughout tropical Africa, Kenya being one ofthe tropical countries.
It also occurs in parts of Asia, Western Pacific, Southand Central America.Plasmodium vivaxIt causes tertianmalaria which causes fever after every second day. The species is found in Asiaand Central America but almost absent in Africa.Plasmodium malariaeCauses tertian malaria.This is a type of malaria which causes fever that recurs after every four days.It is found worldwide but has a very patchy distribution.Plasmodium ovaleThis plasmodium speciescauses tertian malaria. It occurs mainly in tropical West Africa and rarely inthe western pacific.
Malaria is among theleading causesnof death in Kenya especially in children and pregnant women.Treatment of malaria is complicated by the spread of strains of plasmodiumfalciparum resistance to the commonly used antimalarial drugs and the high costand toxicity of the alternative drugs.Transmission of malariaMalaria parasites enterthe human body via the bite of a malaria-carrying anopheles mosquito. Theparasites invade the liver through the blood stream and multiply. During thisperiod the victim doesn’t feel sick.
After nine days, the parasites invade theblood stream and invade the red blood cells. At this stage the parasites arereferred to as merozoites and they continue to multiply. A few days after theappearance of the first symptoms some merozoites develop into gametocytes whichis the sexual stage in the lifecycle and continues to circulate in blood. Thegametocytes are picked by female anopheles mosquitoes during blood-feeding.Malaria preventionPrevention is aimed atavoiding bites of the anopheles mosquito. This can be done through different methodswhich include the following;Wearing of protectiveclothingUse of repellents onexposed skin, mosquito coils and other insecticides.
Sleeping under mosquitonets which are treated with insecticideUse of prophylacticdrugs by visitors to malaria endemic areas to prevent the development of thedisease. These drugs may also be used by children under five years and pregnantwomen in areas of endemicity.