On the 12th day following initial examination, 9 days after completion of chloroquine treatment, and 3 days after starting primaquine treatment, the patient presented with a 3-day history of chills, sweating, malaise, headache, and loss of appetite, but no history of fever. Since he suspected side effects of primaquine, he had stopped taking it. Thick and thin blood films were now positive for P falciparum (parasite density, 0.2%). The ICT was positive for
both, HRP-2 and aldolase. CRP was 89.7 mg/L and creatinine 110 µmol/L. All other laboratory tests were normal. The patient was hospitalized and treated with artemether–lumefantrine. He recovered quickly and was discharged after 3 days. Blood films on days 3 and 7 following treatment were negative. Two blood samples were available
for retrospective polymerase chain reaction (PCR) analysis,2–5 ie, one collected at the initial presentation and one from the second disease episode 12 days later. Species-specific DNA Damage inhibitor PCR assays confirmed the presence of P ovale in the initial sample, but also revealed P falciparum-specific DNA. The second sample was negative for P ovale but positive for P falciparum. Comparing the P falciparum isolates from the initial and the second sample by typing the polymorphic Selleck Crizotinib msp1/2 genes indicated the persistence of one parasite clone over time and the presence of at least one other clone in the second sample. Lastly, typing for parasite alleles associated with P falciparum chloroquine resistance
showed their presence (pfmdr 86Y-184Y-1246Y; pfcrt 76T) in both the initial and the subsequent isolate. We describe a case of P falciparum malaria in a returned traveler from Nigeria, 9 days after completing chloroquine treatment for confirmed tertian malaria caused by P ovale. Mixed-species infections are a frequent phenomenon in malaria, Montelukast Sodium but due to its shorter incubation period, P falciparum in most cases becomes manifest first. Also, rather P ovale tends to be missed in mixed infections because of its notoriously low parasite density. In our re-presenting patient, the absence of fever, the history of a recently completed malaria therapy, the initial absence of P falciparum in microscopy, and the initially negative ICT could have led to missing the diagnosis of the potentially fatal falciparum malaria. Consecutive infections in the 3-week travel period, first with P ovale, then with P falciparum, are the most likely explanation for laboratory findings and clinical course of this case. Considering that the patient had annually traveled to Nigeria during the preceding 10 years, a late relapse from a previous P ovale infection coinciding with a newly acquired P falciparum infection could be an alternative possibility. All microscopic examinations and laboratory tests were performed by highly experienced personnel. The ICT produces reliable results,6 and the combination of blood film microscopy and ICT is widely used in the diagnosis of malaria.