Imported non-Plasmodium falciparum malaria: a five-year prospective study in a European referral center.

From 2000 to 2005, we investigated prospectively 98 cases of imported non-Plasmodium falciparum malaria (48 Plasmodium vivax, 34 P. ovale, and 16 P. malariae). Latency period between return and clinical attack exceeded three months in 40% of the patients. It was longer in travelers who had taken chemoprophylaxis. Time to diagnosis was longer in patients with P. malariae infection and in those with late-onset first attack. Parasite density was often lower than 500/microL, especially in P. ovale malaria. Relapses were diagnosed in 18% of all malaria episodes. Eight (17%) P. vivax and 2 (6%) P. ovale malaria episodes were due to relapse despite standard primaquine therapy. Diagnosis of imported non-falciparum malaria is often challenged by long latency period and low parasite density. In addition, the substantial relapse rate despite standard primaquine therapy supports the use of a higher dose of primaquine to eradicate P. vivax and P. ovale malaria effectively.