Malaria clinical characteristics

This patient also illustrates the importance of a travel history in clinical medicine. Her intermittent fevers came with striking regularity on alternate days, a history that suggests malaria in an individual who has been in an area in which malaria is known to exist. Her flank pain was not due to a urinary tract infection, but was actually related to the splenic enlargement that is so characteristic of malaria. 

The clinical symptoms of malaria infections are exclusively attributable to parasites in the erythrocytic stage. The rupture of infected erythrocytes is associated with the release into the blood stream of cell debris responsible for the characteristic fever spike patterns. In the lethal cases, a specific protein produced by the protozoan is embedded into the cell membrane of the infected erythrocyte and, as a consequence of this modification, the erythrocyte sticks to the walls of capillaries causing obstruction of vessels. When this mechanism operates at the level of brain vessels, the loss of consciousness is the first symptom, but, if this form of cerebral malaria is not treated immediately, it is soon followed by death. 

Plasmodium vivax, the cause of benign tertian malaria, produces milder clinical attacks than those of P. falciparum, and death is uncommon even in untreated cases. The build-up of immunity in the host rapidly controls the infection and schizonts disappear from the blood stream. The exo-erythro-cytic forms in the liver, unaffected by immunity, continue asexual division and reinvade the circulation when immunity has fallen once more these relapses are characteristic of vivax malaria and occur for at least two years after the primary infection. Infections due to P. ovale also follow a tertian pattern, but are much milder and more responsive to therapy than those due to P. vivax and relapses are less frequent. Infections due to both these parasites often display a prolonged incubation period between the primary infection and the development of malarial symptoms. P. vivax is widely distributed north and south of the equator, extending from the tropics to the temperate zones, while P. ovale is restricted to tropical Africa and the western Pacific. 

The presence of parasites certainly impairs appetite, and hence diminishes food intake, under some conditions. Anorexia is characteristic of the clinical picture of recurrent malaria and even more so of trypanosomiasis. Patients suffering from these conditions waste, often quite rapidly, and diminished intake is undoubtedly a factor in the causation of this loss of weight. 

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