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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 102, Num. s1, 2007, pp. 45-46
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Memórias
do
Instituto
Oswaldo
Cruz,
Vol.
102,
No.
Suppl.
I,
2007,
pp.
45-46
Epidemiological,
social,
and
control
determinants
of
Chagas
disease
in
Central
America
and
Mexico
-
Group
discussion
Rodrigo
Zeledón/+, Carlos Ponce*, Jorge F Méndez-Galván**
Laboratorio de Zoonosis, Escuela de Medicina Veterinaria, Universidad Nacional, Heredia, Costa Rica *Secretaría de Salud, Tegucigalpa, Honduras **Secretaría de Salud, Mexico D.F.
+Corresponding
author:
rodrigozeledon@ice.co.cr
Received
4
July
2007
Accepted
3
September
2007
Code
Number:
oc07133
The existence of Chagas disease in Central America was reported for the first time in El Salvador in 1913, four years after its discovery in Brazil. At that time only Triatoma dimidiata was known as a vector, but two years later, in the same country, Rhodnius prolixus was discovered, which is a more efficient vector and now considered to be an introduced species in the area.
Several epidemiological and clinical studies have shown that, with the exception of Belize, the disease is endemic in all Central American countries and in certain areas has become a serious public health problem. This led the health authorities of the countries to launch the Central American Initiative for the control of Chagas disease in 1997. Since that date, several actions have taken place, aiming to eliminate R. prolixus from the region, lower vectorial transmission by T. dimidiata, and control transmission by blood transfusion.
SUMMARY
OF THE DISCUSSION OF DR PONCE PAPER
Dr
Zeledón - I would like to add two important epidemiological
facts related to the situation in Nicaragua: the recent finding
of R. pallescens in the Department Rio San Juan, on the border
with Costa Rica, and the presence, in some departments of the northeast
and southeast of the country, of T. ryckmani.
The
presence of a species of Rhodnius in Rio San Juan, led the
Ministry of Health personnel to spray 2000 houses with insecticide
convinced it was R. prolixus until it was realized that the
species present in the area was actually R. pallescens. The
latter has been found mainly in the peridomiciles but in at least
four houses some nymphs were also found indoors, suggesting an initiation
of colonization of those houses. A serological survey in school
children yielded 6.7% of positive tests and in spite of the occasional
finding of T. dimidiata, R. pallescens seem to be
an important vector in the area. On the Costa Rican side, R.
pallescens is only a visitor of houses and the seroprevalence
there, also in school children, is low (0.24%). In both sides across
the border, R. pallescens has been found in palm trees (Attalea
butyracea).
In relation
to T. ryckmani, the species is becoming a frequent visitor
inside and outside houses where adults are attracted to lights.
In Guatemala, the species has been found living in bromeliads of
the genus Tillandsia in semiarid regions of the country and
in a few instances it is able to colonize human dwellings. The bromeliads
where this bug breeds, are used locally for decorations and are
also exported abroad and this could become a mechanism for dissemination
of the insect.
Another
aspect worth mentioning is in reference to environmental management
methods for the control of T. dimidiata as was recommended
in a technical workshop on the species held in San Salvador in 2002.
A pilot project was implemented in Costa Rica by modifying the environment
around a group of houses in order to destroy the peridomestic habitats
and make difficult the colonization of the bug in those areas, with
very promising results.
Going
back to the hypothesis that R. prolixus is an exotic species
in Central America, the idea originated in 1995 in the ECLAT meeting
of Santo Domingo de los Colorados, Ecuador. After the meeting, Dr
Ponce was able to transmit the idea of a possible elimination of
the species to the Minister of Health of Honduras who meanwhile
was able to convince the health authorities of the other countries
to include this premise as an objective of the Central American
Initiative for the control of Chagas diseases, which was created,
also at the request of Honduran authorities, two years later. This
is a good example of a scientist transferring knowledge and advising
a politician, leading to the political will of converting it into
action.
Dr
Ponce - It is possible that R. prolixus could disappear
from Central America within the next two years.
Dr
Silveira - It is unacceptable as an aim of the Central American
Initiative just the reduction of the infestation by T. dimidiata.
Reduction to which level? Does it correspond to the control of the
domiciliary transmission or just to the interruption of transmission?
In the case of autochthonous vectors the "possible" level
of control of the vector is the elimination of its intradomiciliary
colonies avoiding its re-colonization through common entomological
surveillance actions.
Dr
Ponce - I agree.
Dr
Silveira - Was the protocol for interventions on R. pallescens in Panama, proposed by a team during an international evaluation
in that country, finally applied?
Dr
Ponce - Not yet due to changes in personnel in the country but
is being considered at present.
Dr
Pinto Dias - Has the malaria campaign in El Salvador had a role
in the disappearance of R. prolixus in the country?
Dr
Ponce - It is a combination of two things: insecticide spraying
and house improvement (property right changes, currency remittance
from abroad, and new settlements in rural areas).
Dr
Pinto Dias - What is the etiological treatment you are using
in children?
Dr
Ponce - Benznidazole and nifurtimox are currently used and in
this respect I would like to stress the role played by "Doctors
without borders" in Central America. Serological surveys in
children less than 15 years old are being carried out in the area.
Dr
Storino - I would like to emphasize the focalized nature of
transmission and to suggest performing ECG's in persons older than
40 years and correlate the findings with serology.
Dr
Ponce - New protocols for field studies are now under preparation.
Dr
Ault - I am interested in community participation in relation
to housing facilities and how this is related to the different ethnic
groups.
Dr
Ponce - Makes reference to the native origin of certain plant
materials for building houses such as grass or palm thatched roofs,
which may become risk factors.
Dr
Méndez-Galván - Calls attention to the need to
learn more about prevalence, morbidity and mortality of the disease
in the area. Reliable information is needed for the policy makers
to transform it into actions. Measuring and pondering risk factors
in transmission is needed.
Dr
Torrico - How is the epidemiological vigilance done in Central
America? Does the community participate in it? Is there any environmental
impact due to the modification of houses and what is the acceptance
on the part of the inhabitants? What are the clinical characteristics
in acute and chronic cases?
Dr
Ponce - There are agreements with the communities to define
the improvements to the houses with a minimum of environmental impact.
In general, the acceptance is very good with the necessary cultural
adjustments. Community participation in the intervened areas is
broad, not only in the epidemiological surveillance, but also in
relation to the insecticide spraying, etiological treatment, and
dwelling improvement. All the clinical and pathological features
reported in South America for acute cases are seen in Central America
and Chagas cardiopathy is common in endemic areas but megacolon
and megaesophagus cases are uncommon.
Dr
Junqueira - How do you manage the possible cross reactions with Trypanosoma rangeli?
Dr
Ponce - With the reagents we are using now, there is no problem
in this respect because there are no cross reactions.
Copyright
2007
Instituto
Oswaldo
Cruz
-
Fiocruz
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