We present the diagnostically challenging case of a 51-year-old Japane
se male who visited Papua New Guinea for one month. Approximately a mo
nth after returning to Japan, he experienced a high fever. Malaria was
suspected and he was admitted to Tsukuba University Hospital. Althoug
h the blood smear did not reveal the malarial parasite, a diagnosis of
malaria was made using an indirect fluorescent antibody test (IFAT).
The patient was treated and discharged but symptoms returned three mon
ths later. This time, the blood smear was positive for malarial parasi
tes. IFAT was useful in this case for the early diagnosis of Plasmodiu
m vivax and for ruling out infection by Plasmodium falciparum.