Malaria refers to a widespread blood-borne disease that is spread mainly by mosquitoes in tropical climates. The illness impacts the lives of millions of people in Africa, Asia, the Middle East, South, Central and North America, the Caribbean and the Pacific Islands. Other popular names for this serious illness include: swamp fever, marsh fever, jungle fever, blackwater fever, and ague.
Definition & Facts
Scientists learned in 1880 that the Plasmodium parasite causes malaria, a blood-borne disease which continues to pose a serious global health threat in this century. The United States Centers for Disease Control and Prevention estimates that during 2013 alone, 198 million cases of malaria occurred in the world. Some half a million people perished as a result of this disease.
Malaria has become endemic in some tropical locations. People who reside in these places sometimes, but not always, develop a degree of immunity to malaria. In recent years, 1,500 to 2,000 cases of malaria have occurred in the United States, primarily among people who traveled abroad to tropical areas with endemic malaria.
Symptoms & Complaints
One of the most significant features of malaria involves periodic relapses. Patients recover from the initial symptoms, but then regularly go through bouts of high fever and acute illness again at recurring intervals. The frequency of relapses depends upon the particular species of Plasmodium infecting the patient. For instance, Plasmodium vivax may cause recurring bouts of fever every other day, or even daily. Plasmodium falciparum infections create irregular relapses.
Malaria contributes to secondary health problems in some people. For instance, the most severe infections caused by Plasmodium falciparum may result in the clogging of small blood vessels in certain organ systems. Patients may suffer adverse health complications as a result of damage to the spleen, liver, gastrointestinal tract, brain, lungs or kidneys. Plasmodium vivax infections may lead to a rupture of the spleen in some patients, although fortunately this complication occurs very rarely.
Infected female Anopheline mosquitoes transmit malaria most frequently. Mosquitoes, winged gnat-like insects that feed on blood from humans and animals, flourish in many tropical locations near bodies of water. When an infected Anopheles mosquito bites, it releases the tiny protozoal parasite, Plasmodium into the bloodstream in its saliva. Several varieties of Plasmodium can cause malaria, including P. falciparum, Plasmodium ovale, P. vivax and Plasmodium malariae.
The protozoal parasite lives inside cells in the bloodstream. The Plasmodium that have been transmitted with mosquito saliva eventually infect red blood cells in human beings, causing malarial disease. Patients suffer relapses of malaria whenever the parasite reproduces and a new generation emerges to infect more blood cells. Malaria in rare cases also spreads through blood-borne exchanges. Donations of infected human blood for transfusions and the sharing of hypodermic needles by infected intravenous drug addicts both transmit this disease.
Diagnosis & Tests
The time between the bite of an infected Anopheles mosquito and the occurrence of malarial symptoms varies, depending upon the species of Plasmodium involved in causing the disease. Usually, the incubation period required for distinct species of the Plasmodium parasite covers these time frames:
- P falciparum: 12 days
- P. ovale: 14 days
- P. vivax: 14 days
- P. malariae: 30 days
However, some strains of P. ovale and P. vivax won't cause visible symptoms until eight to ten months or more following transmission. An antigen-based rapid diagnostic test ("RDT") sometimes assists clinicians in confirming a malarial infection. Some reliable polymerase chain reaction tests have been developed, but these testing procedures often prove too costly for frequent use by hospitals in malaria-endemic areas.
Physicians confirm a malaria diagnosis by observing Plasmodium parasites on blood films. Antibodies in blood caused by exposure to malaria may persist for many years following a malarial infection. Their presence indicates past malarial exposure, but won't confirm an ongoing infection.
Treatment & Therapy
Health authorities recommend obtaining prompt treatment for malaria, because of the potential this disease holds to cause serious, and even fatal, complications. Treatment involves the administration of drugs that attack the parasite, based on the specific type of Plasmodium. In the past, chloroquine, quinine, and primaquine have proven effective in treating different types of malaria. One significant problem has concerned reports of increased resistance of some parasites to widely used anti-malarial drugs. Antimalarial medications are typically given as part of a combination therapy which may reduce resistance to any given drug.
Prevention & Prophylaxis
People who don't possess any natural immunity often use chemoprophylaxis as a way to reduce their risk of exposure when they travel in tropical areas. They may take hydroxychloroquine during periods of travel, for instance.
Spraying planes and vehicles that have traveled in regions where Anopheles mosquito populations reside with insecticides reduces the migration of this mosquito to other locations. Recently, some researchers have attempted to genetically modify both Anopheles mosquitoes and Plasmodium parasites in an effort to combat the spread of malaria.