Prior to the appearance of DDT, control of mosquitoes depended primarily on measures designed to reduce larval populations, either by application of larvicides by or elimination of the breeding habitats by drainage, filling, or impounding. Each locality in which mosquito control is desired presents its own problems of water management. Urban malaria in Karachi, Pakistan, is endemic because A. stephensi finds breeding habitats in pools resulting from leaks in the piped water system, in household water storage containers, and in effluents from sewage treatment plants. Bombay is cited as an example of control of A. stephensi by a program enforcing mosquito-proofing of overhead water storage tanks.
Drainage of a breeding site eliminated a focus of malaria near Port-au-Prince, Haiti, in 1969. The ditches not only drained off surface water, but allowed sea water to flush into the area at high tides. Also, during the dry season the ditches contained enough water to insure survival of fish and other predators of mosquito larvae.
In El Salvador, a prolific source of A. albimanus is an area called “estero” behind the sand beach of the ocean, where fresh water accumulates at the beginning of the rainy season. Eventually enough water accumulates to breach the sand retaining dam; then the estero is drained at low tide and flooded with sea water at high tide. This eliminates breeding of A. albimanus. Control should therefore be possible by digging ditches through the sand dam of the beach just before the beginning of the rainy season, so that the high tides could perform their flushing and salting actions before breeding becomes intense.
Water management is not necessarily expensive; it may be beneficial to agriculture as well as to mosquito control, and should be a vital part of planning for malaria control.