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MALARIA: Obstacles and Opportunities
the archetypal urban vector of South Asia). This type of mosquito, which develops in domestic water sources such as wells, cisterns, and household water containers, is responsible for malaria transmission in Delhi, Karachi, Madras, and other urban centers of the Indian subcontinent.
Urban malaria may also occur when sprawling urban settlements encroach on the rural habitats of malaria vectors not usually found in city environments. This occurs in semiurban African villages where the African savannah paradigm predominates. It is important to differentiate these two situations, however, as malaria control strategies will be different even if the vector is the same. Similarly, the densely populated ramshackle settlements associated with gold mines in the Amazon basin support a type of urban malaria, which is actually the result of people moving into areas of forest malaria transmission. In areas of urban malaria, larval control may be a realistic option for reducing malaria transmission, particularly if communities become actively involved. Residual spraying of houses may also be feasible in such settings.
Plains Malaria Associated with Traditional Agriculture Malaria transmission in plains villages involved in subsistence agriculture is usually of low to moderate intensity and fluctuates with the seasons. Such areas are prone to epidemics, particularly in association with early and prolonged rainy seasons. The predominant parasite is often P. vivax. While devastating epidemics are seldom seen, and childhood mortality is not a significant feature as it is with African savannah malaria, this type of malaria can cause chronic debility and suboptimal agricultural productivity. Malaria of this type is widely seen in South Asia and Central America.
Seashore Malaria Many seashore areas of the tropics pose a malaria threat to residents and visitors alike. Such areas are becoming more and more important economically to poor countries as tourists search out unspoiled “tropical paradises” suitable as vacation sites and large numbers of workers come to support the industry. Port areas also offer the potential for malaria transmission and may be the source of infected mosquitoes transported by ships to other regions or of malaria imported by infected seamen to other countries.
Seashore malaria may be transmitted by mosquitoes that breed in brackish water such as the South China Sea. In Africa, the seashore resorts of Kenya provide another example of this type of malaria. Because there is often the potential for successful malaria control efforts, and because of the income generated by tourism, expensive interventions may be more acceptable and sustainable in these areas.
Most of the world's malaria problem can be characterized according to the paradigms described above. Certain other types represent combina-