Failure of atovaquone-proguanil chemoprophylaxis and choloroquine treatment in Plasmodium malariae infection

Summary Plasmodium malariae causes 'quartan malaria', which can be found in most of the major malaria endemic areas. Infections are characterized by low grade parasitaemia, an erythrocytic cycle of 72 hours, a slow pre-erythrocytic development and an extremely variable incubation period. P. malariae accounts for approximately 1-2% of all malaria cases and infections with this parasite are only rarely seen in travelers. Relatively little is known about the efficacy of commonly used chemoprophylactic and therapeutic antimalarials. We report a diagnostic challenge with two patients who developed a symptomatic P. malariae infection despite chemoprophylaxis with atovaquone/proguanil. In one of these individuals, a recurrence of P. malariae occurred despite treatment with chloroquine.