Endemic malaria no longer occurs in most temperate-zone countries and in many areas of subtropical countries; it is still, however, a major cause of ill health in many tropical and other subtropical areas. The disease is responsible for an estimated 1 million deaths per year globally, mostly in young children in Africa; high transmission areas occur throughout tropical Africa, in the southwestern Pacific, in forested areas of South America (e.g. Brazil), in southeastern Asia, and in parts of the Indian sub-continent. Ovale malaria occurs mainly in sub-Saharan Africa, where vivax malaria is much less frequent.
The development and the rapid spread of antimalarial drug resistance in Plasmodium falciparum has been one of the greatest threats to malaria control. Resistance to chloroquine, previously the most widely used antimalarial drug, is widespread, with a few exceptional areas where chloroquine remains effective (Central America west of the Panama Canal, Haiti and the Dominican Republic). Resistance in P. falciparum has also developed to sulfadoxine-pyrimethamine (Amazon Region, southeast Asia, sub-Saharan Africa) and mefloquine (parts of southeast Asia). Resistance has affected all the other antimalarial drugs to different degrees, and is aggravated by cross-resistance between medicines. Sulfadoxine-pyrimethamine, which replaced chloroquine, became almost totally ineffective in Thailand and neighboring countries at the beginning of the 1980s, and this resistance spread rapidly to South America and east Africa. Resistance to quinine and mefloquine is found mainly in Thailand and Cambodia. Sporadic cases of prophylactic failure of mefloquine in travelers and therapeutic failure with amino-alcohols have been reported in Africa, South America, and in other Asian countries. So far, no resistance to artemisinin or artemisinin derivative has been reported, although some decrease in in vitro sensitivity has been reported in China and increased parasite clearance time after treatment with artemisinin-based combination therapy or artesunate monotherapy has been reported at the Thai-Cambodian border.
Most P. vivax malaria infections remain sensitive to chloroquine. However, in recent years, chloroquine resistance of P. vivax has been reported in southeast Asia, in South America, and even in Africa. The relapsing hepatic stages of some P. vivax strains may also be relatively tolerant to primaquine, but its optimum regimen has not been fully defined.
Current information on drug-resistant malaria is published annually by CDC (Health Information for International Travel), and can be found at:
- or on the CDC Malaria website, at:
- and by WHO, at:
- and in International Travel and Health
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