Discovered in 1909, Chagas disease was progressively shown
to be widespread throughout Latin America, affecting millions of rural people
with a high impact on morbidity and mortality. With no vaccine or specific
treatment available for large-scale public health interventions, the main
control strategy relies on prevention of transmission, principally by eliminating
the domestic insect vectors and control of transmission by blood transfusion.
Vector control activities began in the 1940s, initially by means of housing
improvement and then through insecticide spraying following successful field
trials in Brazil (Bambui Research Centre), with similar results soon reproduced
in São Paulo, Argentina, Venezuela and Chile. But national control
programmes only began to be implemented after the 1970s, when technical
questions were overcome and the scientific demonstration of the high social
impact of Chagas disease was used to encourage political determination in
favour of national campaigns (mainly in Brazil). Similarly, large-scale
screening of infected blood donors in Latin America only began in the 1980s
following the emergence of AIDS.
By the end of the last century it became clear that continuous control
in contiguous endemic areas could lead to the elimination of the most highly
domestic vector populations - especially
Triatoma infestans
and
Rhodnius prolixus
- as well as substantial reductions of other widespread species such as
T. brasiliensis
,
T. sordida
, and
T. dimidiata
, leading in turn to interruption of disease transmission to rural people.
The social impact of Chagas disease control can now be readily demonstrated
by the disappearance of acute cases and of new infections in younger age
groups, as well as progressive reductions of mortality and morbidity rates
in controlled areas. In economic terms, the cost-benefit relationship between
intervention (insecticide spraying, serology in blood banks) and the reduction
of Chagas disease (in terms of medical and social care and improved productivity)
is highly positive. Effective control of Chagas disease is now seen as an
attainable goal that depends primarily on maintaining political will, so
that the major constraints involve problems associated with the decentralisation
of public health services and the progressive political disinterest in Chagas
disease. Counterbalancing this are the political and technical cooperation
strategies such as the "Southern Cone Initiative" launched in
1991. This international approach, coordinated by PAHO, has been highly
successful, already reaching elimination of Chagas disease transmission
in Uruguay, Chile, and large parts of Brazil and Argentina. The Southern
Cone Initiative also helped to stimulate control campaigns in other countries
of the region (Paraguay, Bolivia, Peru) which have also reached tangible
regional successes. This model of international activity has been shown
to be feasible and effective, with similar initiatives developed since 1997
in the Andean Region and in Central America. At present, Mexico and the
Amazon Region remain as the next major challenges. With consolidation of
operational programmes in all endemic countries, the future focus will be
on epidemiological surveillance and care of those people already infected.
In political terms, the control of Chagas disease in Latin America can be
considered, so far, as a victory for international scientific cooperation,
but will require continuing political commitment for sustained success.