Chloroquine resistant falciparum malaria in Malaya

About 10 per cent. of troops involved in jungle operations along the Thai-Malayan border in North Perlis during August to October, 1962, developed malaria in spite of proguanil prophylaxis. The majority of these had Plasmodium falciparum infections, many of which relapsed after larger than usual dosages of chloroquine. Ten of the cases were studied in more or less detail, and clinical evidence of chloroquine as well as proguanil resistance was obtained. In two cases, laboratory confirmation of the clinical evidence was obtained as relapse occurred in the presence of plasma chloroquine levels generally considered therapeutic.