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In Malaysia, there are 434 species of mosquitos, representing 20 genera. Of these, 75 species are Anopheles.
There are four species of human malaria. Plasmodium falciparum (Welsh, 1897), causes ''tertian-malignant'' type of malaria, is responsible for more than 95% of the total malaria cases in the world, and is the most important malaria species in Malaysia.
Most of the continental United States has Anopheles mosquitoes (particularly An. freeborni and An. quadrimaculatus), which can spread malaria.

Anopheles, the only known carrier of malaria, also transmits filariasis and encephalitis. Anopheles mosquitoes are easily recognized in their resting position, in which the proboscis, head, and body are held in a straight line to each other but at an angle to the surface. The spotted coloring on the wings results from colored scales. Egg laying usually occurs in water containing heavy vegetation. The female deposits her eggs singly on the water's surface. Anopheles larvae lie parallel to the water surface and breathe through posterior spiracular plates on the abdomen instead of through a tube, as do most other mosquito larvae. The life cycle is from 18 days to several weeks.

The natural history of malaria involves cyclical infection of humans and female Anopheles mosquitoes. In humans, the parasites grow and multiply first in the liver cells and then in the red cells of the blood. In the blood, successive broods of parasites grow inside the red cells and destroy them, releasing daughter parasites (“merozoites”) that continue the cycle by invading other red cells.

The blood-stage parasites are those that cause the symptoms of malaria. When certain forms of blood-stage parasites (gametocytes, which occur in male and female forms) are ingested during blood feeding by a female Anopheles mosquito, they mate in the gut of the mosquito and begin a cycle of growth and multiplication in the mosquito. After 10-18 days, a form of the parasite called a sporozoite migrates to the mosquito’s salivary glands. When the Anopheles mosquito takes a blood meal on another human, anticoagulant saliva is injected together with the sporozoites, which migrate to the liver, thereby beginning a new cycle.

Thus the infected mosquito carries the disease from one human to another (acting as a “vector”), while infected humans transmit the parasite to the mosquito, In contrast to the human host, the mosquito vector does not suffer from the presence of the parasites.