Tropical infections and the lungs

Abstract

Tropical area refers to the geographic region locating between the Tropic of Cancer and the Tropic of Capricorn. The countries included in this area located in Asia, Africa, Central and South America, Northern Australia and Pacific islands, are mostly developing or underdeveloped. High temperatures and high humidity characterize the climate in the tropics. Temperature is the major governing factor for the distribution of many tropical diseases because many reservoirs such as arthropods, snails and vertebrates have life cycles that are limited by heat and cold. Most of them cannot survive in cold and dry weather in temperate zones so their distributions are confined to tropics. The limited distribution of reservoirs, many of which also serve as vectors, determines the spread of the agents and then the diseases. Rainfall, flooding and other sources of water are essential for the increasing numbers of some vectors and reservoirs and thus increasing transmission of the agents and diseases. Geographic barriers such as rivers, mountain ranges and oceans can also limit the spread of some tropical infectious diseases requiring vectors or intermediate hosts for their transmission to human. In addition, human behaviour can influence the distribution of all tropical infectious diseases, especially those caused by organisms which are transmitted from person to person. Such agents may persist wherever people travel and may not be affected by environmental factors whereas agents requiring a vector and/or intermediate host for human transmission may have a restricted distribution due to environmental factors (climate, rainfall, and geographic barriers) as well as human behaviour. The common human behaviour in the tropics favouring disease transmissions are eating poorly cooked or raw intermediate (or paratenic) host tissue; bared foot walking on soil ground, muddy area, or in natural water-source; eating by using fingers to pick up the food into the mouth; and sleeping without nets. Public health measures are very important in the control of various tropical infections. These measures include improved sanitation, raised standard of living, vaccination, vector or reservoir control by source reduction and pesticides, improvement of housing, drug prophylaxis, effective treatment and health education to avoid risky behaviour for acquiring the diseases. Infected travellers and immigrants from tropical countries are responsible for the spreading of person-to-person transmitted diseases to non-tropical countries. Importing of reservoir hosts or vectors that can be viable in non-tropical areas may also promote emergence of tropical infectious diseases in non-tropical countries. Pulmonary involvement of tropical infections that are still mainly confined to tropical areas is the focus of this chapter. These diseases may mainly affect the lungs or their pulmonary manifestations is important for making diagnosis, selecting treatment and predicting outcome of the systemic disease. Nowadays, pulmonary tuberculosis is a global epidemic disease and thus not included. © 2005 Hong Kong University Press, HKU. All righrts reserved.