Disease. malariae malaria, quartan malaria,
Geographic Distribution.orldwide, malaria usually restricted to tropical and subtropical areas and altitudes below 1,500 m. P. malariae is found in most endemic areas, especially throughout sub-Saharan Africa
Infection rate. WHO estimates that yearly 300-500 million cases of malaria occur and more than 1 million people die of malaria. P. malariae is much less common than the other species.
Life cycle. A malaria-infected female Anopheles mosquito inoculates sporozoites into the human host during a blood meal. Sporozoites infect liver cells and mature into schizonts, which rupture and release merozoites (exo-erythrocytic schizogony). The merozoites infect red blood cells. The ring stage trophozoites mature into schizonts, which rupture releasing merozoites (erythrocytic schizogony). Some parasites differentiate into sexual erythrocytic stages (gametocytes). The gametocytes are ingested by an Anopheles mosquito during a blood meal. The microgametes penetrate the macrogametes generating zygotes in the mosquito's stomach. The zygotes become ookinetes and invade the midgut wall where they develop into oocysts. The oocysts grow, rupture, and release sporozoites, which make their way to the mosquito's salivary glands (sporogonic cycle).
Morphology. Ring: sturdy cytoplasm; large chromatin, Trophozoite: compact cytoplasm; large chromatin; occasional band forms. Schizont: mature = 6 to 12 merozoites. Gametocyte: round to oval; compact; may almost fill RBC.
Pathogenesis and clinical symptoms. The disease is caused by the direct effects of red cell invasion and destruction by the asexual parasite and the host's reaction. The symptoms of uncomplicated malaria can be rather non-specific. The most frequent symptoms include fever and chills, which can be accompanied by headache, myalgias, arthralgias, weakness, vomiting, and diarrhea. Other clinical features include splenomegaly, anemia, thrombocytopenia.
Diagnosis. Microscopic identification is the method most frequently used to demonstrate an active infection. Molecular diagnosis techniques can complement microscopy. Antibody Detection can detect past (not necessarily active) infections.
Prevention. Personal protection against mosquito bites is the first line of defence against malaria. In addition, travellers should take chemoprophylaxis where appropriate.