MONITORING FOR MEFLOQUINE-RESISTANT PLASMODIUM-FALCIPARUM IN AFRICA -IMPLICATIONS FOR TRAVELERS HEALTH

The effectiveness of mefloquine to prevent malaria caused by Plasmodiu m falciparum is influenced by the sensitivity of the malaria parasites to this drug. Concern has been raised that resistance to mefloquine m ay develop in sub-Saharan Africa as has been observed in Southeast Asi a. Case reports, along with blood smears to confirm the diagnosis and blood samples to determine the mefloquine concentration, were provided on any Peace Corps volunteer serving in sub-Saharan Africa who was di agnosed with malaria. We defined prophylaxis failures probably due to mefloquine resistance as patients with P. falciparum malaria confirmed at the Centers for Disease Control and Prevention, reported complianc e with prophylaxis, no ingestion of mefloquine between date of illness onset and date of blood drawing, and a mefloquine level greater than or equal to 620 ng/ml in blood drawn within five days of onset of illn ess. Between January 1, 1991 and September 6, 1996, 44 (31%) of 140 vo lunteers with confirmed P. falciparum had blood drawn within five days of onset of illness. Twenty-nine (66%) had not fully complied with pr ophylaxis. Five of 15 prophylaxis failures in four countries had meflo quine levels greater than or equal to 620 ng/ml. Failure of mefloquine prophylaxis is primarily due to noncompliance. Evidence of probable r esistance to mefloquine among strains of P. falciparum was found in fi ve Peace Corps volunteers in sub-Saharan Africa. Clusters of well-docu mented prophylaxis failures need to be followed-up by therapeutic in v ivo studies to document parasite resistance to mefloquine. Reduced sen sitivity to mefloquine does not (yet) appear to be a significant probl em in sub-Saharan Africa.