Malaria

Malaria is a parasitic disease spread by mosquitos that causes chills and fever; potentially fatal complications in the liver, kidneys, blood, and brain are possible.

Not to be confused with miliaria.

Infection with malaria parasites may result in a wide variety of symptoms, ranging from absent or very mild symptoms to severe disease and even death. Malaria disease can be categorized as uncomplicated or severe (complicated). In general, malaria is a curable disease if diagnosed and treated promptly and correctly.

All the clinical symptoms associated with malaria are caused by the asexual erythrocytic or blood stage parasites. When the parasite develops in the erythrocyte, numerous known and unknown waste substances such as hemozoin pigment and other toxic factors accumulate in the infected red blood cell. These are dumped into the bloodstream when the infected cells lyse and release invasive merozoites. The hemozoin and other toxic factors such as glucose phosphate isomerase (GPI) stimulate macrophages and other cells to produce cytokines and other soluble factors which act to produce fever and rigors and probably influence other severe pathophysiology associated with malaria.

Plasmodium falciparum-infected erythrocytes, particularly those with mature trophozoites, adhere to the vascular endothelium of venular blood vessel walls and do not freely circulate in the blood. When this sequestration of infected erythrocytes occurs in the vessels of the brain it is believed to be a factor in causing the severe disease syndrome known as cerebral malaria, which is associated with high mortality.

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Incubation Period

Following the infective bite by the Anopheles mosquito, a period of time (the “incubation period”) goes by before the first symptoms appear. The incubation period in most cases varies from 7 to 30 days. The shorter periods are observed most frequently with P. falciparum and the longer ones with P. malariae.

Antimalarial drugs taken for prophylaxis by travelers can delay the appearance of malaria symptoms by weeks or months, long after the traveler has left the malaria-endemic area. (This can happen particularly with P. vivax and P. ovale, both of which can produce dormant liver stage parasites; the liver stages may reactivate and cause disease months after the infective mosquito bite.)

Such long delays between exposure and development of symptoms can result in misdiagnosis or delayed diagnosis because of reduced clinical suspicion by the health-care provider. Returned travelers should always remind their health-care providers of any travel in areas where malaria occurs during the past 12 months.

Uncomplicated Malaria

The classical (but rarely observed) malaria attack lasts 6–10 hours. It consists of

A cold stage (sensation of cold, shivering)
A hot stage (fever, headaches, vomiting; seizures in young children); and
Finally a sweating stage (sweats, return to normal temperature, tiredness).
Classically (but infrequently observed) the attacks occur every second day with the “tertian” parasites (P. falciparum, P. vivax, and P. ovale) and every third day with the “quartan” parasite (P. malariae).

More commonly, the patient presents with a combination of the following symptoms:

• Fever
• Chills
• Sweats
• Headaches
• Nausea and vomiting
• Body aches
• General malaise

In countries where cases of malaria are infrequent, these symptoms may be attributed to influenza, a cold, or other common infections, especially if malaria is not suspected. Conversely, in countries where malaria is frequent, residents often recognize the symptoms as malaria and treat themselves without seeking diagnostic confirmation (“presumptive treatment”).
Physical findings may include the following:

• Elevated temperatures
• Perspiration
• Weakness
• Enlarged spleen
• Mild jaundice
• Enlargement of the liver
• Increased respiratory rate

Diagnosis of malaria depends on the demonstration of parasites in the blood, usually by microscopy. Additional laboratory findings may include mild anemia, mild decrease in blood platelets (thrombocytopenia), elevation of bilirubin, and elevation of aminotransferases.

Severe Malaria

Severe malaria occurs when infections are complicated by serious organ failures or abnormalities in the patient’s blood or metabolism. The manifestations of severe malaria include the following:

• Cerebral malaria, with abnormal behavior, impairment of consciousness, seizures, coma, or other neurologic abnormalities
• Severe anemia due to hemolysis (destruction of the red blood cells)
• Hemoglobinuria (hemoglobin in the urine) due to hemolysis
• Acute respiratory distress syndrome (ARDS), an inflammatory reaction in the lungs that inhibits oxygen exchange, which may occur even after the parasite counts have decreased in response to treatment
• Abnormalities in blood coagulation
• Low blood pressure caused by cardiovascular collapse
• Acute kidney injury
• Hyperparasitemia, where more than 5% of the red blood cells are infected by malaria parasites
• Metabolic acidosis (excessive acidity in the blood and tissue fluids), often in association with
• hypoglycemia
• Hypoglycemia (low blood glucose). Hypoglycemia may also occur in pregnant women with uncomplicated malaria, or after treatment with quinine.

Severe malaria is a medical emergency and should be treated urgently and aggressively.

Malaria Relapses

In P. vivax and P. ovale infections, patients having recovered from the first episode of illness may suffer several additional attacks (“relapses”) after months or even years without symptoms. Relapses occur because P. vivax and P. ovale have dormant liver stage parasites (“hypnozoites”) that may reactivate. Treatment to reduce the chance of such relapses is available and should follow treatment of the first attack.

Other Manifestations of Malaria

• Neurologic defects may occasionally persist following cerebral malaria, especially in children. Such defects include trouble with movements (ataxia), palsies, speech difficulties, deafness, and blindness.
  
• Recurrent infections with P. falciparum may result in severe anemia. This occurs especially in young children in tropical Africa with frequent infections that are inadequately treated.
  
• Malaria during pregnancy (especially P. falciparum) may cause severe disease in the mother, and may lead to premature delivery or delivery of a low-birth-weight baby.
  
• On rare occasions, P. vivax malaria can cause rupture of the spleen.
  
• Nephrotic syndrome (a chronic, severe kidney disease) can result from chronic or repeated infections with P. malariae.
  
• Hyperreactive malarial splenomegaly (also called “tropical splenomegaly syndrome”) occurs infrequently and is attributed to an abnormal immune response to repeated malarial infections. The disease is marked by a very enlarged spleen and liver, abnormal immunologic findings, anemia, and a susceptibility to other infections (such as skin or respiratory infections).

Glossary of malaria terms

This glossary contains definitions for significant terms associated with the study, treatment, and prevention of malaria.

• Airport malaria - Malaria cases that result from the transmission of malaria by mosquitoes to individuals in an airport area, far from endemic regions.
• Anopheles - A genus of mosquitoes that is the primary vector for malaria transmission.
• Anopheles claviger - A species of the Anopheles mosquitoes, found in Europe and parts of the Middle East.
• Anopheles dirus - A highly efficient malaria vector found in South and Southeast Asia.
• Anopheles sinensis - A species of Anopheles mosquito common in parts of Asia, known to transmit malaria and filariasis.
• Apicoplast - A plastid found in the cells of the Plasmodium parasite, involved in fatty acid synthesis.
• ArtemiFlow - An initiative aimed at producing artemisinin, a key component of malaria treatment, in a cost-effective manner.
• Artesunate/mefloquine - A combination therapy used for the treatment of uncomplicated Plasmodium falciparum malaria.
• Attractive toxic sugar baits - An innovative mosquito control method that lures and kills mosquitoes by using sugar solutions mixed with insecticides.
• Beauveria bassiana - A fungus used as a biological control agent against malaria mosquitoes.
• Blackwater fever - A severe complication of malaria, characterized by hemoglobinuria and kidney failure.
• Blantyre coma scale - A medical scale used to measure the depth of coma in children with cerebral malaria.
• Buffy coat - A fraction of an anticoagulated blood sample that contains most of the white blood cells and platelets following centrifugation.
• Circumsporozoite protein - A protein on the surface of the Plasmodium sporozoites, involved in malaria infection.
• Congenital malaria - Malaria infection transmitted from a mother to her fetus.
• Cuban fever - Historical term for yellow fever, often confused with malaria due to similar symptoms.
• DDT - Dichloro-diphenyl-trichloroethane, a synthetic insecticide used in mosquito control programs.
• Debug Project - A project aimed at reducing the population of disease-carrying mosquitoes through genetic engineering.
• Delftia tsuruhatensis - A bacterium studied for its potential to disrupt malaria transmission by interfering with Plasmodium development in mosquitoes.
• Febris - An archaic term for fever, often used in historical texts on malaria.
• Food vacuole - A digestive organelle within the Plasmodium parasite where hemoglobin degradation occurs.
• Global Malaria Action Plan - A comprehensive strategy by the Roll Back Malaria Partnership to reduce malaria incidence and mortality.
• Groningen epidemic - A historical malaria outbreak in the province of Groningen, Netherlands.
• Hemozoin - A crystalline byproduct of hemoglobin digestion by Plasmodium parasites, also known as malaria pigment.
• History of malaria - An overview of the discovery, understanding, and efforts to control malaria throughout human history.
• Indoor residual spraying - The application of insecticides on the interior walls of homes to kill or repel mosquitoes.
• Intermittent fever - Fever that occurs at intervals, characteristic of certain forms of malaria.
• Malaria Control Project - Initiatives aimed at reducing malaria transmission and mortality.
• Malaria Day in the Americas - An observance day to raise awareness and promote efforts to combat malaria in the Americas.
• Malaria Journal - A scientific journal publishing research on all aspects of malaria.
• Malaria antigen detection tests - Diagnostic tests that identify malaria antigens to confirm infection.
• Malaria prophylaxis - Preventive treatment against malaria, typically involving antimalarial medications.
• Malaria therapy - The intentional use of malaria infection for therapeutic purposes, historically used to treat syphilis.
• Malaria vaccine - Vaccines developed to prevent malaria. The PfSPZ Vaccine is an example.
• Malarial nephropathy - Kidney disease resulting from chronic or severe malaria infection.
• Mass drug administration - The distribution of antimalarial drugs to an entire population to reduce malaria transmission.
• Merosome - A membrane-bound vesicle released by liver cells infected with malaria parasites, involved in parasite escape from the liver.
• Merozoite surface protein - Proteins located on the surface of merozoites, the invasive form of malaria parasites that infect red blood cells.
• Mosquito control - Methods used to control or eliminate mosquito populations to reduce the spread of mosquito-borne diseases like malaria.
• Mosquito laser - A technology developed to target and kill flying mosquitoes, aiming to reduce malaria transmission.
• Mosquito-malaria theory - The scientific theory that establishes mosquitoes as the vectors for malaria transmission.
• PfSPZ Vaccine - A malaria vaccine candidate consisting of sporozoites, the infective form of the Plasmodium parasite, to induce immunity.
• Plasmodium - The genus of parasitic protozoa that causes malaria in humans and animals.
• Plasmodium falciparum - The most deadly species of the Plasmodium parasites, responsible for the majority of severe malaria cases and deaths.
• Plasmodium girardi - A species of Plasmodium that infects rodents, studied for its implications in understanding malaria.
• Plasmodium vivax - A species of Plasmodium that causes a less severe form of malaria but can lead to relapses.
• Pregnancy-associated malaria - Malaria infection in pregnant women, which poses significant risks to both the mother and the fetus.
• Quartan fever - A form of malaria with a fever pattern recurring every third day, associated with infection by Plasmodium malariae.
• Schüffner's dots - Small, pink or red spots seen in red blood cells infected with certain species of Plasmodium, such as Plasmodium vivax.
• Serratia - A genus of bacteria, some species of which have been investigated for their potential to block malaria transmission.
• Tropical splenomegaly syndrome - A condition often associated with chronic malaria infection, characterized by an enlarged spleen.
• World Malaria Day - An international observance commemorated every year on 25 April, to highlight the global effort to control malaria.

Malaria Resources
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Malaria Resources
Latest articles Most recent articles Ongoing trials	Wikipedia