Drug resistance among malaria and other parasites

Abstract

Recent decades have witnessed the emergence and spread of parasites resistant to standard drug therapies, particularly malaria. Chloroquine-resistant Plasmodium falciparum has now spread to most malarial areas, and resistance to other antimalarial drugs, including mefloquine and sulfadoxine-pyrimethamine, have become significant problems in some parts of Southeast Asia and South America. Chloroquine-resistant P. vivax is well established in Papua New Guinea and Indonesia and has been reported in other areas. Trichomonas and Giardia infections resistant to metronidazole have also been documented. This article reviews the current status of drug resistance among parasites, particularly malaria, and offers strategies for managing patients with these infections.

PIP: Reviewed in this article is the research literature on issues related to the development, spread, and impact of drug resistant malaria and current recommendations on chemoprophylaxis for the prevention of malaria. Also examined is metronidazole resistance in both Giardia and Trichomonas and the possibility of ivermectin resistance in human filariasis. Consistent themes in the literature on drug resistance include widespread and uncontrolled use of drugs, heavy reliance on a small number of drugs, use of single drug therapy, poor compliance with recommended treatment regimens, and slow development of new therapeutic alternatives. The way existing drugs are administered must be improved so their usefulness can be sustained. New drugs should not be introduced before they are needed to delay selection of resistant parasite strains. Mass drug administration should be used cautiously. Where possible, treatment should be based on a specific diagnosis. Efforts are needed to improve patient compliance with multiple-dose treatments. Although multidrug therapy has been proposed as an effective way to limit resistance, it poses problems in terms of increased cost and complexity. Finally, vaccines, appropriate and sustainable vector avoidance or elimination strategies, environmental control, and human behavior modification are important to reduce the need for drug therapy.