No abstract

We carried out a series of malaria studies in Robek , Flores, Indonesia, a coastal village of 900 farmers and fishermen where malaria is hyperendemic by parasite rate and holoendemic by spleen rate. The studies showed that: (i) 28 of 31 isolates (90%) of Plasmodium falciparum were resistant to chloroquine in vitro, (ii) 3 of 12 isolates (25%) were resistant at the R-11 level in vivo, (iii) 376 P. falciparum infections occurred in 301 individuals during one year, (iv) no villagers who were treated with chloroquine for P. falciparum infections during the year died, and (v) increasing the dosage of chloroquine base from 15 to 25 to 37.5 mg/kg led to improved clearing of parasitaemia. We conclude that chloroquine can still be used as the primary antimalarial in Robek , but the dosage may have to be increased to clear parasitaemia.

One hundred cases of slide-confirmed Plasmodium falciparum malaria admitted to the San Lazaro Hospital, Manila, Philippines were screened for in vitro resistance to chloroquine, quinine, amodiaquine and mefloquine using the microtechnique. 59 of the 100 primary parasite isolates produced schizonts, whereas the remaining 41 isolates did not. 51 of the 59 isolates tested were resistant in vitro to chloroquine and eight were sensitive. In contrast, three of the primary isolates were resistant to quinine, three showed resistance to amodiaquine and four were mefloquine-resistant. 43 of the strains judged chloroquine-resistant in vitro were fully in vitro sensitive to amodiaquine, quinine and mefloquine. One chloroquine-resistant isolate was also resistant to quinine alone. Three isolates that were resistant to chloroquine were also resistant to amodiaquine. An additional three were cross-resistant to chloroquine and mefloquine. A single isolate was found to be resistant to chloroquine, quinine and mefloquine and another was cross-resistant to chloroquine, quinine and amodiaquine. All strains demonstrating in vitro resistance to amodiaquine, quinine or mefloquine also showed in vitro resistance to chloroquine. The parasites in 22 patients showed in vivo resistance to chloroquine therapy. 86% were of the R1 type, 9% were R2 and 5% R3. All 22 patients demonstrating in vivo resistance to chloroquine showed in vitro resistance.