Analysis of the principal problems impeding normal development of malaria eradication programs.

The problems currently impeding the advance of anti-malaria programs in the Americas fall into several different categories. These include vector resistance to insecticides, parasite resistance to chloroquine, human behavior patterns which promote human/vector contact or reduce the impact of control efforts, and developments affecting operation, administration, and financing of the control program itself. Vector resistance, of course, may be either physiological, behavioral, or both. With regard to physiological resistance, four of the ten anopheline species considered important in the Americas have shown physiological resistance to at least one insecticide in some part of their range. One of the most serious and complex problems of this kind currently confronts El Salvador, where generalized Anopheles albimanus resistance to both DDT and propoxur (along with operational and administrative difficulties) has sparked a considerable rise in malaria incidence. In many places, such physiological resistance is closely related to indiscriminate use of insecticides in agriculture. Here corrdinated action by each country's malaria, health, and agricultural services is urgently needed. Besides physiological factors, the article reviews ways in which vector behavior creates problems. With regard to residual spraying on the inside walls of houses, such behavioral resistance may involve failure to come to rest after biting, resting for only a short period, resting on unsprayed surfaces, or resting only outside the house. Concerning the malaria parasite itself, Plasmodium falciparum resistance to chloroquine has been found in parts of Brazil, Columbia, Guyana, Panama, Surinam, and Venezuela over the past 15 years. Furthermore, the rapidity of modern travel has greatly increased the chances for importing malaria cases from areas of P. falciparum resistance into areas now free of this problem.