Transcript Chagas disease.

Chagas disease
Paul R. Earl
Facultad de Ciencias Biológicas
Universidad Autónoma de Nuevo León
San Nicolás NL, 66451, Mexico
[email protected]
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, alfacypermethrin, 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 therapeutic 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?