STUDIES ON A STRAIN OF CHLOROQUINE-RESISTANT PLASMODIUM FALCIPARUM FROM THAILAND.

Infections with a strain of Plasmodium falciparum from Thailand, termed the Thailand (JHK) strain, were established in 25 non-immune volunteers in a non-endemic area under conditions precluding reinfection. Eleven volunteers received chloroquine in usually curative doses on a three-day schedule during acute clinical malaria attacks. Volunteers also received (again during acute clinical attacks) hydroxychloroquine, amodiaquine, mepacrine, pyrimethamine, proguanil or 377-C-54, alone or in combination. These regimens failed, both before and after passage of the strain through mosquitos, to effect radical cure of the infection. Radical cure was achieved by administration of 1350 mg or 1620 mg of quinine base daily for seven days.The authors point out that resistance to chloroquine by P. falciparum is being recognized with increasing frequency in South America and South-East Asia, and that the effect of this on global chemotherapy of malaria may be serious.