TABLE 2-1 Classifications of Malaria Endemicity as Defined by Rates in Children Two to Nine Years Old

Classification

Spleen Ratea (%)

Parasite Rateb (%)

Holoendemic

>75

>75 (in infants)

Hyperendemic

51-75

51-75

Mesoendemic

11-50

11-50

Hypoendemic

0-10

<10

a Originally proposed at the WHO Malaria Conference in Equatorial Africa (1951) and subsequently amended by Molineaux (1988).

b Metselaar and van Thiel (1959), as found in Molineaux (1988).

and adults suffer severe disease. In meso- and hypoendemic regions, the frequency of infection is generally low, but epidemics may be devastating.

By definition, stable malaria transmission is intense, robust, and very difficult to interrupt. This type of disease transmission can occur where there are very low densities of mosquitoes, particularly anthropophilic and long-lived vectors such as An. gambiae and those with similar characteristics. In stable malaria transmission, the human population generally acquires a partial immunity to malaria, and morbidity and mortality are largely limited to young children and pregnant women. Conversely, unstable malaria occurs in regions of intermittent malaria transmission where there is little or no acquired population immunity and the risk of epidemic malaria is high. As a rule, as endemicity decreases, transmission becomes less stable and the risk of epidemics increases.

MALARIA CONTROL

Malaria control efforts traditionally have relied on the provision of proven antimalarial drugs, on environmental sanitation, and on the application of insecticides.

Drugs

Antimalarial drugs are used to prevent the onset of disease, to treat clinical cases in individuals, and to prevent disease transmission within populations. Some drugs, including doxycycline, proguanil, pyrimethamine, and primaquine, attack the liver stage, preventing the release of parasites into the bloodstream. Others, such as chloroquine, quinine, sulfadoxinepyrimethamine, and mefloquine, kill the parasite within red blood cells.

The emergence and spread of drug resistant strains of the most dangerous of the four human malaria parasites, P. falciparum, has reemphasized



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