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This article discusses the importance of eradicating insect vectors, such as triatomid bugs, to control Chagas disease. It also explores approaches for improved prevention, diagnosis, and treatment, as well as the role of political will in achieving eradication. The use of insecticides, community involvement, and the impact of socioeconomic factors are also highlighted.
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Chagas diseasePaul R. EarlFacultad de Ciencias BiológicasUniversidad Autónoma de Nuevo LeónSan Nicolás NL, 66451, Mexicopearl@dsi.uanl.mx
Policies. The handling of trypanosomiasis and leishmaniasis throughout the subtropical and tropical world like the management of malaria depends upon the eventual eradication of the insect vectors, not upon individual treatments. Disease eradication should lead to a better standard of living in a still more industrial society. The focus at present is house spraying with residual insecticides like lindane, or fumigation, especially against triatomid bugs. Fumigation with ambdacyhalothrin, alfacyper-methrin, cyfluthrin, deltamethrin and others is recommended as applicable from dengue to malaria.
Socioeconomic and behavioral research associated lieshmaniasis and trypanosomiasis. Strategies and budgets for eradication include better educated awareness and improved home management. School children are the logical target for good PH education. Country immigrants with city children create a fast intergration. More, Chagas disease is rural.
Epidemiology of transmission, immune response, morbidity and mortality. Definition and education of the relationship between parasite diversity and immune responses, analysis of the relationships among transmission, infection, disease patterns and deaths in order to design effective intervention strategies.
Evaluation of community-based large-scale preventive and thera-peutic interventions. Preparation and development of communities for large-scale intervention studies; development of appropriate strategies/tools for study implementation; development of a databank for validating and documenting knowledge of indigenous management also reaching out to geographic and satelite data. Nevertheless, the center here is, again, political power or better political will, regardless of how biological facts may be understood.
Health policy, systems and services research. Analysis of access and use (or neglect) of health facilities; development of strategies for improved collaboration between national health authorities, public and private/traditional health care providers and the exploration of health sector reforms to enhance control and surveillance.
Severity of the pathogenesis. Studies on parasite-vector-host factors involved in severe diseases, cardiopathy and analysis of the neurological and other deficits associated with severe disease. Veterinary research on reservoir hosts is included.
Functional genomics of parasite and vectors. Novel approaches based on recent advances in molecular biology, gene technology and genome studies in elucidating host-parasite relationships and mechanisms such as transgenes and insertions. Transgenic vectors might be produced that are incompetent to transmit disease.
Vector population, insecticide resistance and alternative insecticides.Application of newly developed molecular tools for studies on vector biology, feeding behaviour, vector capacity, insecticide resistance and population genetics with the aim of identifying and developing effective strategies for vector control in focal, low and high transmission settings, including the genetic development of incompetent insect vectors. Pyrethroid-impregnated bed nets offer protection.
Drug resistance, chemotherapy, chemoprophylaxis and drug policy.Development of strategies for rapid mapping of drug resistance; innovative approaches for preventing, retarding and reversing drug resistance; as well as the development of strategies for replacing first line drugs.
Political will and Chagas eradication. The Southern Cone Initiative is the shining example. Political alliance, determination and adequate longterm funding have vastly reduced domicilary triatomids, and vigilance has reduced percent of blood transfusions that are Chagas positive. Transfusion is the second most common transmission route of Chagas disease in many Latin American countries. Seropositivities like 8-9 % are common in Mexican urban locations that are associated with continuous migration from the country to the city.
Under the Pan-American Health Organization (PAHO), the ministries of health from the 7 countries that belong to the South Cone during a meeting in Brasília in July 1991, recognized the huge size of the problem and committed themselves to the eradication of T. infestants on the region and also to eliminate the transfusional transmission of T. cruzi, through strengthening the blood banks and through the effective control of donors.
Main research topics.Topics of current interest include: 1) Incidence of infection in young age groups, 2) Discovery and development of new chemotherapeutic and diagnostic tools, 3) Basic and clinical research networks and partnerships with the private sector, and 4) Susceptibility and resistance to insecticides.
Political will and house spraying.Work with the community to achieve a change of attitude and practices related to house infestation for the next 10 years. An educative social effort will be needed to justify covering house-to-house expenses involving many many thousands of houses. The expected economic returns exceed largely the cost of any such program in cost/benefit studies. For example, burn one gamma-HCH fumigant tablet of 3.1 g/bedroom. To illustrate, the annual treatment costs of one Chagas patient can help maintain 25 households free from triatomid bugs.
Spraying or fumigating inside houses revisited.Few persons understand mosquito control beyond the spray can level. Often houses with doors and windows open are sprayed by aerosols from a truck. Such results may be almost impossible to evaluate. Spraying inside by backpack is much better. If DDT is used, warn the householders of possible staining of walls.
The Brazilian story.Determination involves political will which in its turn is influenced by PH education. Does the public know the risk it is taking?The Brazilian political will success story depends on a) the biotechnical knowhow and b) the determination to do an honest job. Native biotechnology dating from 1909 and Carlos Chagas (1897-1934) initiated this outrageous success.
Is leishmaniasis essentially the same disease as trypanosomiasis?We have the vertebrate hosts, mostly mammals, the various arthropod vectors and the protozoan parasites on 5 continents, yet mainly in the tropics, because sometimes cold temperature limit the vector’s range. Then we have some system of classifying these trypanosomes and leishmanias that are of course all pathogens of the blood.
Chagas disease. form, the amastigote mainly in tissues, and as a trypomastigote form in the blood. The vector for Chagas disease are bugs (Hemiptera) such a Triatoma infestans. They ingest trypomastigotes mainly or rarely amastigotes when they feed on an infected mammal. In the vector, the parasite reproduces asexually as epimastigotes, and metacyclic trypomastigotes are found in the vector's hindgut.
Conclusions. Where are the populations at risk? Who is concerned with such facts? What are the methods of eradication or control, and what are the investments? Is cardiopathy a serious issue? Where and for whom? Are the rural poor to be helped by the industrial residents who are better off? Are household pets well studied as reservoirs? Why is high prevalence of T. cruzi in humans sometimes hidden?
