Malaria is a serious and sometimes life-threatening disease prevalent in humid and tropical regions of the world. Caused by parasitic infection, malaria is often treatable and preventable, but many die of the condition each year. According to statistics by the World Health Organization, 2008 saw almost a million deaths as a result of the condition. Understanding malaria transmission is a major part of limiting the infection's ability to spread; in almost all cases, malaria transmission is the result of bites from infected mosquitoes.
There are four main types of malaria that are transmittable to humans, and each can be carried by a family of mosquitoes known as Anopheles, or malaria vectors. The connection between mosquitoes and malaria transmission was first made by doctor and scientist Alphonse Laveran in the 19th century. The disease had been familiar for centuries, but common wisdom attributed it to the humid air, rather than a parasitic infection. Though Laveran's hypothesis that malaria transmission was conducted through mosquitoes was met with considerable skepticism, he was later awarded a Nobel Prize for his work on the subject.
Mosquitoes feed by sucking small amounts of blood from human or animal hosts. If a mosquito bites a malaria-infected host, some of the infected red blood cells can be picked up and transferred through the next bite or several bites. Once implanted into a new host, the parasites take up residence in the liver, where they may remain for several months or even years, causing no symptoms or discomfort. When the parasites leave the liver, they cause severe symptoms as they multiply throughout the bloodstream, including high fevers, vomiting, convulsions, blindness, chills, and even death.
Keys to preventing malaria transmission include both preventative measures and comprehensive treatment of malaria victims. To prevent bites from occurring, people are advised to use insect repellent, hang mosquito nets over doors, windows and beds, and kill any mosquitoes that appear. Most malaria vectors bite between dusk and dawn, leading some experts to suggest remaining indoors entirely during those hours.
Many forms of malaria are treatable with drugs, which can eventually kill off all parasites in the body. However, since the parasites can lay dormant for so long, people may not be aware they have the infection for many months. Since malaria parasites live in the red blood cells, transmission can also occur if a blood or organ donor has an unsuspected case of the infection. For that reason, many experts urge blood and molecular screening of potential donors in areas with high rates of malaria transmission.