Drug-resistant falciparum malaria from Cambodia and Malaya

Five strains of P. falciparum suspected of being chloroquine resistant were established in eight prisoner volunteers. Two of these strains originated from Cambodia and are referred to as Cambodian I and II. Three are from natural infections in Malaya and are referred to as Malayan I, II and III. These strains were studied for their response to one to five anti-malarial drugs; namely, chloroquine, proguanil, mepacrine, pyrimethamine and quinine. The Cambodian I strain was susceptible to chloroquine when the 1.5 gramme regimen of the base was given. The Cambodian II and the Malayan II strains were resistant to chloroquine, proguanil, mepacrine and pyrimethamine but susceptible to quinine. The Malayan I strain was resistant to chloroquine and to proguanil but susceptible to pyrimethamine and to quinine. The Malayan III strain was resistant to chloroquine, proguanil and pyrimethamine but susceptible to mepacrine and to quinine. Quinine was the only anti-malarial to which all strains were susceptible. A comparison between these strains and the chloroquine resistant strains from Colombia and Thailand is presented.