A Traveler's Fever

Roberta Capp, MD; Natan Noviski, MD


December 11, 2017

The clinical presentation of malaria can vary widely and depends on the species of Plasmodium involved. Common symptoms include fever, malaise, myalgia, and headache, which may be accompanied by cough, abdominal pain, or diarrhea. Because these symptoms are nonspecific, malaria should be considered in all febrile travelers, regardless of their clinical presentation. In fact, approximately 78%-100% of patients presenting with malaria are febrile when they are first examined.

The classically described fever patterns are rarely observed; however, when these fevers do occur at 48-hour to 72-hour intervals, this finding is virtually pathognomonic for P vivaxP ovale, and P malariae infections. This cyclical pattern of symptoms coincides with the regular interval of erythrocyte hemolysis.

Upon examination, splenomegaly is found in 24%-48% of patients, and patients may experience abdominal pain. Severe malaria, usually caused by P falciparum, causes several manifestations, including prostration, impaired consciousness or coma, respiratory distress caused by pulmonary edema and the acute respiratory distress syndrome, seizures, circulatory collapse, abnormal bleeding (including disseminated intravascular coagulopathy), splenic rupture, jaundice, severe anemia, acute renal failure, and acidosis. The level of parasitemia often exceeds 5%.

P knowlesi has been reported to cause sporadic cases of traveler's malaria, mostly in fringe areas in Southeast Asia. Symptoms may be atypical. Organ failure may occur, and deaths have been reported. P knowlesi is not associated with relapse.

The diagnosis of malaria is made by examination of both thin and thick blood smears. These smears are used to quantify the level of parasitemia, which is used to guide treatment. If the first smear is negative, it should be repeated at 12- to 24-hour intervals for 48-72 hours. If the diagnosis is clinically suspected and a sufficient laboratory diagnosis is not possible, empirical treatment for P falciparum should be started because the disease can be fatal if left untreated. Rapid detection assays and molecular tools, such as polymerase chain reaction, may also be used to confirm the diagnosis.

Other laboratory findings, such as normocytic anemia, thrombocytopenia, low white blood cell count, elevated lactate dehydrogenase level, and elevated bilirubin level, are nonspecific but may provide clues to the diagnosis.


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