Malaria in Travelers: Epidemiology, Clinical Aspects, and Treatment

Malaria is still a major cause of morbidity and mortality among travelers. The two most common imported species are Plasmodium falciparum and P. vivax. The relative percentage of their occurrence varies between countries. The clinical presentations of the two species are usually indistinguishable. Severe cases, mainly due to P. falciparum, occur in about 10% of travelers, and mortality is about 1-3% of falciparum cases. Delay in diagnosis by physicians who encounter returning febrile travelers continues to be a major reason for poor outcomes. The treatment of falciparum malaria is based on blood stage treatment only. Due to the rapid emergence of drug resistance, there is a pressing need for new drugs. The old drug, quinine, is still very effective, but newer drugs are also available. Atovaqone-proguanil (Malarone) is an oral treatment for uncomplicated malaria cases. Artemisinin-based compounds, which have become drugs of choice in Africa, have been registered in several Western countries as a combination of artemether and lumefantrine. This compound, however, is still not available for parenteral use in cases of severe malaria; thus i.v. quinine/quinidine continues to be used as a single agent. Vivax malaria treatment is still based on chloroquine, as chloroquine resistance is rare. However, the liver-stage drug primaquine is needed for the completion of the treatment. Underdosing of primaquine was the most likely reason for recurrent relapses, and therefore doubling the previously prescribed dose of primaquine has recently been recommended.