RIASSUNTO
Abstract
Ecological principles for the design and implementation of sustainable malaria vector control programmes are outlined and illustrated with the results obtained from successful malaria control programmes in Indonesia and Papua New Guinea. The elements of program design may be applied during planning, construction and subsequent operational phases; and in established projects. The integrated vector control techniques make use of: the ecological characteristics of local vectors; landscape and local topography; and, modern environmentally sound insecticides. There are opportunities to create partnerships between private sector and government and for local job creation.
Baseline ecological and entomological parameters are usually required prior to program implementation, including careful identification of local mosquito species and their breeding habitats. Control decisions are based upon the weekly collection of quantitative data from both human and mosquito populations. An integrated mosquito control program targeting malaria vectors may include; environmental planning and construction controls; ongoing breeding source reduction which may include habitat modification as well as drainage measures; larviciding and appropriate biological controls; residual insecticide applications to dwellings; and, the use of insecticide impregnated bed-nets. The successful impact of these measures on anopheline populations and malaria incidence and prevalence will be illustrated using data collected from locations in Indonesia and Papua New Guinea over the past 6 years. Epidemiological indicators will illustrate control principles and outcomes.
Introduction
Malaria is an ancient disease, which remains a major health problem in the tropical world. It is infecting and killing more people than ever before and is a significant cause of intellectual impairment and economic under-development. The disease is caused by a single celled parasite, Plasmodium, which is transmitted by Anopheles mosquitoes. Strains of the parasite resistant to the drugs commonly available for treatment are becoming increasingly widespread. In many countries, Anopheles mosquitoes have evolved reduced susceptibility to a number of the common insecticides used for their control. The U.S. Agency for International Development has estimated that worldwide, as many as 900 million people were made ill by malaria in 2002. More than 1 million of those victims died. Some estimates rate the mortalities during this period as high as 2.7 million. Although the vast majority of deaths from malaria occur in Africa, the economic cost is high in all of the countries of Africa, Asia, the Pacific Islands and Latin America where the disease is endemic. The World Health Organization estimates the loss to these economies from the disease is in the order of US$ 3-12 billion annually.1
The procedures reported in this paper are based upon control programs implemented over the past decade in Indonesia and Papua New Guinea. Typical regions and target diseases are summarized in Table 1. Four species of Plasmodium parasite are capable of infecting humans, however, P. falciparum and P. vivax are the most common and potentially harmful and only these species will be discussed here.
Resource development projects are frequently associated with rapid local population growth, resulting from both inward migration as well as natural increase. This may lead to dramatic changes in the local or regional landscape, resulting from colonization of land previously allocated for non-intensive uses. Although the resource project may conform to strict international standards of environmental planning and site development, the same may not apply in adjacent, rapidly growing communities. Increased clearing or disturbance of naturally vegetated land is a common outcome of new settlement. In malaria prone areas, the combination of rapidly increasing population and associated land disturbance in situations with minimal planning and development controls may provide ideal conditions for outbreaks or epidemics of the disease. For these reasons, a site-specific malaria survey incorporating both entomological and epidemiological investigations is highly desirable early in a development project cycle.3 Preferably during the advanced exploration or early project planning stage, prior to construction. This early stage usually provides the most opportunities for cost-effective, sustainable, environmental planning and management strategies for malaria control. Nevertheless, an integrated control program may be introduced at any stage during planning and construction, or for established projects.