Malaria is an infectious febrile disease caused by protozoan parasites of the
genus Plasmodium. This disease continues to be widespread outside the United States
in tropical, subtropical, and temperate climates, places where the Anopheles mosquito
breeds. The malarial belt includes parts of Mexico, Haiti, the Dominican Republic,
Honduras, Ecuador, Africa, India, Southeast Asia, and the Philippines.
Malaria is transmitted in three ways: from infected people to healthy people via
mosquito bites (mosquitoes carry the parasite); from hypodermic injections using a
syringe or an infected person and then on a healthy person); and from blood
transfusions (giving blood from an infected person to a healthy person). By far the most
common vector for the malarial parasite is the mosquito. Although there are many
species of mosquitoes, only a few carry human disease parasites. There are four
species of human malarial parasites, all carried by the mosquitoes of the genus
Anopheles. Only the female bites humans. She does so to get the blood she needs for
Figure 4-1. Adult Anopheles mosquito.