Malaria is an infectious disease caused by a group of parasites (protozoa) called Plasmodium, which is transmitted by the bite of female Anopheles mosquitoes. There are 5 known species of Plasmodium responsible for practically all the human malarial cases worldwide. Four of them have been known and studied for a long time, and one has been recently found to be responsible for malaria in macaques, and causes zoonotic malaria, by macaque-to-human spread.
The clinical features of malaria are extremely diverse, and depend on multiple factors, including, but not limited to, the specific causative agent, the geographical area involved, and the biological make-up of the patient in question, itself. They can vary from absent (asymptomatic disease) or mild symptoms, to severe symptoms, and even death. The clinical spectrum of malaria is classified as uncomplicated malaria and severe/complicated malaria.
All the symptoms of malaria are caused due to release of toxic substances from the parasite that infect the red blood cells of patients which then stimulate the immune system of the patient causing certain white blood cells to secrete some chemicals, that then cause fever and rigours and possibly, other more severe features of malaria.
The symptoms of malaria appear after an initial incubation period (time from the bite of the infected mosquito to the onset of symptoms) that ranges from 7-30 days, depending on the causative agent.
Features of Uncomplicated Malaria
Uncomplicated malaria is classically described as proceeding through three stages:
- A cold stage (sensation of cold, shivering)
- A hot stage (fever, headaches, vomiting; seizures in young children)
- A sweating stage (sweats, return to normal temperature, tiredness)
However, this occurrence is quite uncommon.
A combination of the following symptoms is usually seen:
- Nausea, with or without vomiting
- Body aches
- General malaise/ weakness/ lethargy
Physical findings commonly seen include:
- Elevated body temperature
- Excessive sweating
- Enlarged spleen
- Jaundice (yellowish discolouration of skin, eyes, tongue etc.)
- Enlargement of the liver
- Rapid breathing
Features of Severe/ Complicated Malaria
Malaria is said to be severe when organ failure/ abnormalities in blood or metabolism occur as a direct consequence of malaria.
The various manifestations of severe malaria are:
Cerebral malaria – presence of abnormal behavior, impairment or loss of consciousness, seizures, coma, or other neurologic abnormalities.
- Severe anemia due to destruction of red blood cells by the parasite
- Excretion of haemoglobin in the urine due to red blood cell destruction
- Acute respiratory distress syndrome (ARDS) – an inflammatory reaction in the lungs that inhibits oxygen exchange, which may occur even after an initial favourable response to treatment
- Blood coagulation abnormalities
- Low blood pressure
- 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)
- Hypoglycaemia (low blood glucose) – some anti-malarial medicines can also cause hypoglycaemia.
Severe malaria is a medical emergency, and mandates urgent admission and treatment.
It is important to note that some species of Plasmodium have the capability to enter a dormant state in the human hosts, only to be ‘awakened’ much later on, in the face of poor immunity, or stressful conditions, and cause a relapse of malaria that was previously thought to be absent or completely treated.
Malaria can also cause certain long-term manifestations, like, kidney disorders (nephrotic syndrome), persistent neurological deficits (especially in children), severe disease in pregnant women, that can affect the unborn child and cause preterm delivery and low birth weight.
In conclusion, the features of malaria are extremely diverse, and an accurate diagnosis can be quite difficult to make on clinical grounds alone, especially in areas where malaria is not very prevalent.