malaria

malaria
Name	Malaria
Field	Infectious disease, Tropical medicine
Symptoms	Fever, fatigue, vomiting, headaches
Complications	Cerebral malaria, severe anemia, organ failure
Causes	Plasmodium parasites spread by Anopheles mosquitoes
Prevention	Mosquito nets, insecticides, antimalarial medication
Treatment	Antimalarial medication
Frequency	~247 million cases (2021)
Deaths	~619,000 (2021)

malaria is a life-threatening mosquito-borne disease caused by parasitic protozoans of the genus Plasmodium. It is transmitted to humans through the bites of infected female Anopheles mosquitoes. The disease remains a major global health challenge, particularly in tropical and subtropical regions, with significant impacts on public health and economic development.

Overview

The disease is caused by eukaryotic protists belonging to the phylum Apicomplexa. Five species are known to cause the illness in humans, with Plasmodium falciparum and Plasmodium vivax posing the greatest threat. The World Health Organization classifies it as a major priority within its Global Malaria Programme. Historically, the parasite's life cycle was first described by Sir Ronald Ross, who received the Nobel Prize in Physiology or Medicine for his discovery. The Centers for Disease Control and Prevention and other agencies maintain extensive surveillance and research programs focused on its control.

Causes and transmission

Transmission primarily occurs via the bite of an infected female Anopheles gambiae or other Anopheles species. The complex life cycle involves both a human host and the mosquito vector. Sporozoites are injected into the human bloodstream during a blood meal, traveling to the liver to initiate the exoerythrocytic schizogony phase. After maturation, merozoites are released to invade red blood cells, leading to the symptomatic blood stage infection. Other, rarer modes of transmission include blood transfusion, organ transplantation, and congenital transmission from mother to fetus.

Signs and symptoms

Classic symptoms often present as cyclical episodes known as a paroxysm, featuring a cold stage with chills, a hot stage with high fever, and a sweating stage. These correspond with the synchronous rupture of infected erythrocytes. Plasmodium falciparum infection can progress rapidly to severe malaria, characterized by cerebral malaria, severe malarial anemia, acute respiratory distress syndrome, and multiple organ dysfunction syndrome. Plasmodium vivax and Plasmodium ovale can form dormant hypnozoites in the liver, causing relapses months or years later.

Diagnosis and prevention

Definitive diagnosis relies on microscopic examination of Giemsa-stained blood films or rapid diagnostic tests that detect specific parasite antigens. Molecular diagnostics like polymerase chain reaction are used in reference laboratories. Prevention strategies are multifaceted, including vector control through long-lasting insecticidal nets, indoor residual spraying with insecticides like DDT, and chemoprophylaxis for travelers. The RTS,S/AS01 vaccine, developed through a partnership between GlaxoSmithKline and the PATH Malaria Vaccine Initiative, represents a significant advancement.

Treatment and management

Treatment depends on the Plasmodium species, geographic location, and severity of illness. Artemisinin-based combination therapies, such as artemether-lumefantrine, are the first-line treatment for uncomplicated cases caused by Plasmodium falciparum in most endemic regions, as recommended by the World Health Organization. For Plasmodium vivax and Plasmodium ovale, treatment requires adding primaquine or tafenoquine to target hypnozoites and achieve radical cure. Management of severe cases in intensive care unit settings includes intravenous artesunate and supportive care for complications.

Epidemiology and history

The disease imposes the greatest burden in the World Health Organization African Region, particularly in countries like Nigeria, the Democratic Republic of the Congo, Uganda, and Mozambique. Major initiatives for control and elimination are coordinated by the Roll Back Malaria Partnership, the Global Fund to Fight AIDS, Tuberculosis and Malaria, and the President's Malaria Initiative. Historical figures like Alphonse Laveran, who first observed the parasite, and Sir Ronald Ross were pivotal in understanding its transmission. Evidence of the parasite has been found in Ancient Egyptian mummies, and it significantly affected the outcomes of military campaigns, including during the American Civil War and the Pacific War.

Category:Infectious diseases Category:Tropical diseases Category:Mosquito-borne diseases