Infection with malaria parasites may result in a wide variety of symptoms, ranging from absent or very mild symptoms to severe malaria and even death. Malaria disease can be categorized as uncomplicated or severe (complicated), so it is important to know what are the symptoms of malaria.
The incubation period in most cases varies from 7 to 30 days. The shorter periods are observed most often with P. falciparum and the longer ones with P. malariae. (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.
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)
- Finally a sweating stage (sweats, return to normal temperature, tiredness).
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:
- 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 failure
- 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.
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 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.
- Hyper-reactive 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).
Many organizations are involved in malaria prevention and some of these methods are used:
1. Encourage people to sleep under Insecticide-treated nets (ITNs)
2. Oils may be applied to the surface of stagnant water, suffocating the larvae and pupae. Most oils in use today are rapidly biodegraded.
3. Clearing of long bushes around homesteads
4. Use of insecticides to kill the mosquitoes.
Federation of African Medical Students’ Associations
- Anti-inflammatory drugs may improve survival from severe malaria (eurekalert.org)
- Malaria’s genetic secrets open door to new drug targets (fiercebiotechresearch.com)