Abstract

PIP: Chloroquine resistant strains of Plasmodium falciparum were initially reported during the early 1960s and are currently found in many areas of Asia and South America. The prevalence and degree of resistance are increasing in all affected areas, representing a serious setback to antimalaria programs. Alternative drugs are much more expensive and frequently more cumbersome to use. Consequently, it is essential that a concerted effort be made to arrest the spread of resistant strains by developing standardized national policies on drug use. The probable genetics and epidemiology of drug resistance are considered in this report, and attention is directed to the problems involved in its control. Antimalarial drugs interfere with important physiological functions of the parasites. Chloroquine and mepacrine apparently block acid proteases and peptidases in the phagosomes of intraerythrocytic parasites. Circumstantial evidence from "in vitro" tests suggests that strains of P. falciparum from various parts of the world, although primarily susceptible to chloroquine, exhibit, "a priori," different sensitivities. P. falciparum in the Sobat valley of Ethiopia and in central Sudan appears to be significantly less susceptible to chloroquine than the Uganda I strain. There are no indications yet of chloroquine resistance in P. vivax, P. malariae, or P. ovale. The relative prevalence of chloroquine resistant infections and the degree of resistance are still on the increase in all affected areas. The development of drug resistance in areas with previously susceptible parasites has thus far always been associated with the use of the particular medicaments. 4 main factors seem to be involved: the degree of drug pressure; the degree of host/parasite contact; the duration of drug pressure; and the type of drug used. The occurrence of chloroquine resistant falciparum malaria requires the urgent attention of the health authorities and that several operational measures be undertaken. Instructions must be provided concerning the principles of drug use in antimalaria programs in the event of the spread of drug resistance, and these instructions are reviewed. The methods for the monitoring of drug sensitivity are also reviewed. The World Health Organization (WHO) has developed global monitoring program, initially implemented in 1977 in the Southeast Asia Region. Program objectives are identified.