Chloroquine resistance of Plasmodium falciparum in West Irian and East Kalimantan.

Evidence is presented of the chloroquine-resistance in Plasmodium falciparum in West Irian and East Kalimantan as shown by clinical observation and quantitative parasite counts in two patients hospitalized in Tokyo where no natural transmission of malaria occurs. The evidence is supported by the determination of plasma chloroquine levels, and in vitro sensitivity tests. The highest plasma level of chloroquine in the patient infected in West Irian was 197 ng/ml (fourth treatment) and 435 ng/ml (fifth treatment), and that in the patient infected in East Kalimantan was 312 ng/ml. Fifty percent inhibition of maturation was obtained in vitro at 0-6 and 0-62 nM/ml of chloroquine, respectively. Both patients were readically cured by 2 g of sulphadoxine and 100 mg of pyrimethamine given in a single dose.