The etiology of malaria is from the protozoan parasites of the genus Plasmodium with an asexual stage in humans and a sexual stage in mosquitoes. The four genus are P. falciparum, P. vivax, P.ovale, and P. malariae.

The Anopheles mosquito is essential for the development, multiplication, and spread of malarial disease. The bite from an infected female Anopheles mosquito can occur at night, but is particularly noted during dusk and dawn periods and is seen at altitudes less than 2200 meters. Malaria is found throughout the tropical and subtropical areas of the world usually between 45 N and 40 S latitude with 200-300 million infections and 1.5 million deaths estimated per year. Most deaths are attributable to P. falciparum.

Signs may range from asymptomatic (usually semi-immune patient) to a rapidly fatal disease. The nonimmune patient usually has acute onset of fever (102-106°) and rigors (100 percent), headache (66-89 percent), nausea and emesis (41-64 percent), and myalgias (40-57 percent). Physical findings include fever, diaphoresis, tachypnea, conjunctival icterus, occasional pulmonary rales, palpable spleen (49-88 percent) and liver (31-44 percent), and alterations of mentation.

Abnormal laboratory findings reflect the severity of hemolysis.

• CBC: anemia (25-50 percent), leukopenia (25-36 percent), thrombocytopenia (30-80 percent).

• Peripheral Blood Smear: look for malarial parasites (see diagnosis below).

• Urine: + protein, urobilinogen, conjugated bilirubin, and hemoglobin.

• Chemistry Panel (Lytes, Glucose, BUN, CRE): Hypoglycemia is frequently seen in children and pregnant females. Hyponatremia may occur.

• Liver Function Tests: The transaminases AST/ALT are often elevated.

Diagnosis requires a high index of suspicion and demonstration of malarial parasites in the peripheral blood. Smears should be obtained initially every 6-8 hours while the diagnosis is in question for at least 3 days. Smears should be followed every 8-12 hours, if seriously ill, to monitor the effects of therapy and then daily until parasitemia is resolved. Trophozoites should ideally decrease by 75 percent in first 48 hours and disappear within 7 days although gametes may persist. Thin smears are an alternative if the lab is unable to prepare and interpret thick smears.

This can include malaria, typhoid fever or other salmonelloses, dengue, influenza, meningococcemia or other sepsis, amebiasis, relapsing fever, viral encephalitis, rickettsial diseases, leptospirosis, and endocarditis.

A patient with malaria and any one or more of the following should be regarded as complicated: *

• Hyperparasitemia: >3 percent RBC's parasitized.

• Hypoglycemia: Serum glucose <60 mg/dl.

• Severe anemia: Hct <21 percent or a rapidly falling Hct.

• Renal failure: Urine output <400 ml/day, BUN >40 mg/dl or CRE >4 mg/dl.

• Hyponatremia: Serum Na < 125 mg/dl.

• Cerebral malaria: Any history or finding of delirium or decreased level of consciousness.

• Prolonged hyperpyrexia >24 hours.

• High output diarrhea or protracted emesis.

• Any significant cardiac or pulmonary dysfunction.

• Pregnancy: Increased risk to mother and child.

*Cases of complicated malaria should be presumed to be secondary to P. falciparum and should be treated as a medical emergency with parenteral therapy initially.

P. falciparum resistance to chloroquine is wide-spread throughout Asia, Africa, and South America. Only sensitive organisms are reliably found in Central America above Panama, Haiti, the Dominican Republic, and the Middle East. Resistance to sulfadoxine/pyrimethamine (Fansidar) is present in Southeast Asia, Africa, and in the Amazon basin of Brazil. Mefloquine resistance has been widely reported from Southeast Asia and many parts of Africa. P. Vivax chloroquine resistance has been recently described from Papua, New Guinea, and Irian Jaya. P. vivax primaquine resistance has been reported from Southeast Asia and South America.