Malaria Treatment in the United States

Abstract

To the Editor: In their review of the treatment of malaria in the United States, Dr Griffith and colleagues provided a concise summary for clinicians who infrequently encounter malaria. While the information is important, they propose that the second question to be asked when managing malaria is “What is the parasite density?” Although there is an association between the peripheral parasite count and patient outcome, it is a relatively weak one. Other clinical and laboratory variables have stronger prognostic value, particularly acidosis and pulmonary and renal disease. In an international trial, almost 70% of 1050 severe malaria patients had a peripheral parasite count of less than 5%, and the mortality in this population was 18%. Emphasis on a “low” parasite count, rather than disease manifestations, may offer the clinician false reassurance or lead to an underestimation of the contribution of the malaria infection to a patient’s symptoms. The central pathophysiological mechanism in severe malaria is the mechanical microcirculatory obstruction caused by sequestration of infected erythrocytes. This increases as parasites mature during their 48-hour asexual life cycle. Once infected, erythrocytes are adherent to endothelium in the microcirculation; they will no longer appear in the peripheral circulation. Therefore, depending on the stage of the parasites’ life cycle, 2 patients with the same peripheral parasitemia may have as much as a 100fold difference in the total number of parasites in the body. Regarding quinidine, the main parenteral agent discussed in the article, the current World Health Organization treatment guidelines note that quinidine is more toxic than quinine and should only be used if no other effective parenteral drugs are available. The same guidelines recommend artesunate as the treatment of choice in lowtransmission areas, as it has been shown to be associated with a 34.7% relative reduction in mortality compared with quinine; while it is available in many developing countries, it has not yet been approved by the US Food and Drug Administration.