Chagas disease Paul R. Earl Facultad de Ciencias Biol

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Chagas diseasePaul R. EarlFacultad de Ciencias
BiológicasUniversidad Autónoma de Nuevo LeónSan
Nicolás NL, 66451, Mexicopearl_at_dsi.uanl.mx
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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 vectors range. Then we
have some system of classifying these
trypanosomes and leishmanias that are of course
all pathogens of the blood.
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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.
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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?