Clinical Manifestation

·   Symptoms of malaria usually start to appear 10-15 days after the bite of an infected mosquito. 

· The typical prepatent and incubation periods following sporozoite inoculation vary according to species. 

·  The prepatent period is defined as the time between sporozoite inoculation and the appearance of parasites in the blood and represents the duration of the liver stage and the number of merozoites produced. 

·   Incubation periods tend to be a little longer and are defined as the time between sporozoite inoculation and the onset of symptoms.

·   All four species can exhibit non-specific prodromal symptoms a few days before the first febril attack. 

·   These prodromal symptoms are generally described as 'flu-like' and include: headache, slight fever, muscle pain, anorexia, nausea and lassitude. The symptoms tend to correlate with increasing numbers of parasites.

 

·   These prodromal symptoms will be followed by febrile attacks also known as the malarial paroxysms. 

·   These paroxysms will exhibit periodicities of 48 hours(benign tertian) for P. vivax, P. ovale, and P. falciparum, 36-48 hours fever(malignant tertian) for P. falciparum and a 72-hour periodicity(quartan fever) for P. malariae.

 

·  Patients may also exhibit splenomegaly, hepatomegaly (slight jaundice), and hemolytic anemia during the period in which the malaria paroxysms occur.

The Malarial Paroxysm

cold stage hot stage sweating stage feeling of intense cold vigorous shivering lasts 15-60 minutes intense heat dry burning skin throbbing headache lasts 2-6 hours profuse sweating declining temperature exhausted and weak → sleep lasts 2-4 hours

·  The malarial paroxysm usually last 4-8 hours and begins with a sudden onset of chills(cold stage). 

·  Immediately following this cold stage is the hot stage. The patient feels an intense heat accompanied by severe headache. fatigue, dizziness, anorexia, myalgia, and nausea will often be associated with the hot stage. 

·   Next a period of profuse sweating will ensue and the fever will start to decline. The patient is exhausted and weak and will usually fall asleep.

·  After awake the patient usually feels well, other than being tired, and does not exhibit symptoms until the onset of the next paroxysm.

	A typical pattern of temperature (fever) in relation to blood-stage schizogony for the human malarial parasites. The fever paroxysm corresponds to the period of infected erythrocyte rupture and merozoite invasion. (Figure modified from Neva and Brown, Basic Clinical Parasitology, 6th ed., 1994.