Health Surveillance and Disease Management / Communicable Diseases / Chagas Disease
IPA*: Initiative of the Andean Countries to Control Vectoral and Transfusional Transmission of Chagas Disease
Current situation in the Andean Subregion
Disease in Process of Elimination
One hundred years after the discovery of Chagas disease, the countries of the Southern Cone (Argentina, Brazil, Chile, Paraguay and Uruguay) have brought about a reduction in the incidence of the diseases by controlling vector-borne transmission through fumigation of infested dwellings with residual insecticides and by controlling transfusional transfusion by screening blood samples, all thanks to the political and financial commitment of their Ministries of Health.
Initiatives were started in 1997 in the Andean countries and in Central America to interrupt vector-borne and transfusion transmission. Data on the progress of these two Initiatives indicate that the goal of interrupting Chagas transmission in the entire Hemisphere is a mid-term objective that will surely be reached by around 2010, as laid down in Resolution WHA51.14 adopted by the World Health Assembly (WHA) in 1998.
It can therefore be concluded that Chagas disease is on its way to hemispheric elimination.
For various reasons, progress has been very slow and control interventions vis-à-vis the target species in question have still not been settled in all the geographical areas that these insects occupy. Partly, the reasons are due to ignorance concerning the biological characteristics of these vector populations and consequent uncertainty as to which measures and strategies of control would be most appropriately applied in the respective geographical areas. For Venezuela, Colombia, Ecuador, and northern Peru, the main vector species present important similarities that make it possible to address them similarly throughout the subregion, based on strategies developed in Venezuela during the 1960s that were progressively adopted in the Southern Cone and Central American subregions. Meetings were held to review the vector species in each country in order to offer a viable strategy for implementation throughout endemic areas.
Target Vector Species
The only vulnerable element in the chain of transmission of Chagas disease is the vector.
Given the constraints of resources throughout the Andean Pact subregion, it is unlikely that rapid elimination of all domestic triatomine populations will be viable. As a result, IPA proposes a strategy of more progressive implementation based on serological and entomological stratification at municipal level.
In the absence of any means to prevent human infection by immunization of the susceptible population (because no vaccine exists) and by exhaustion of the sources of infection, the only measures providing specific protection are those directed to household vectors.
Sufficient technology is already available to control vector-borne transmission of Chagas disease in the household environment. The systematized utilization of residual insecticides has been repeatedly demonstrated as effective and capable of bringing about a reduction in transmission.
Household colonization and the size of domiciliary populations (critical density) are essential conditions for transmission. Clearly, there is always a chance for human infection to occur accidentally.
Geographic Information Systems (GIS)
The collection, storage, and analysis of geographical data constitutes a fundamental instrument for evaluating the activities of Chagas vector-control program and for providing orientation to guide the efforts of field teams. Vector-control programs that initiated their activities more recently have had the opportunity to utilize new computer technologies related to the development of geographic information systems, newly-available information provided by satellite, and recent progress in methods of spatial epidemiology.
A GIS is a computer tool that makes it possible to obtain, store, recover, administer, analyze, and represent data associated with spatial attributes.
These properties offer an important basis for examining different epidemiological aspects of Chagas disease. A GIS can be used to locate sites where vectors are found and where cases occur, and to establish spatio-temporal relationships between vectors and cases using environmental variables. The need to integrate epidemiological data derived from different sources promoted the development of GISs and tools to carry out spatial analysis. These new instruments overcame the difficulty of utilizing traditional parametric statistical tests that violated one of its basic premises regarding independence of observations.
* The acronym "IPA" comes from the Spanish Iniciativa de los Países Andinos = Initiative of the Andean Countries.
History of the Initiative
The 1st Meeting of the Andean Countries on Chagas disease vectors was held from 18–20 February 1997 in Bogotá, Colombia. It provided a the space in which each participating country took on commitments aimed at meeting the objectives of eliminating vector-borne and transfusion transmission of American trypanosomiasis in the Andean Region.
In May 1998, the 51st World Health Assembly—encouraged by advances in the control of vector-borne Chagas transmission in the Southern Cone, and in recognition of the decision adopted in the 1st Meeting of the Andean Countries in Bogotá as well as of Central American Ministers in Tegucigalpa—defined the year 2010 as its deadline for achieving the goal of eliminating vector-borne transmission of the T. cruzi.
The 2nd Meeting was held in Maracay, Aragua, Venezuela, from 8-9 April 1999. It proposed different areas of action, among them joint procurement of input; operations research in entomology, seroepidemiology and sociology; quality control of the serological tests for clinical diagnosis and screening of blood banks; and mechanisms for drug supply and availability.
The 3rd Meeting was held in Guayaquil, Ecuador from 7–8 June 2000. It established joint criteria regarding decentralization processes, placing emphasis on the decentralization of the entomological, epidemiological, clinical and laboratory knowledge of Chagas disease. Moreover, it defined courses of action for managing blood supplies, reiterating quality issues and the need for working with national legislatures to modernize laws governing blood and the steering role of ministries of health.
The 4th Meeting was held in Guayaquil, Ecuador, from 7–9 May 2003. It made various proposals, among them to develop a standardization process to define variables, criteria, and evaluation guidelines for Chagas control; to permanently integrate country delegates specializing in blood services into the Intergovernmental Commission; to continue the entomological surveillance activities; to develop diagnostic and treatment capability; to conduct research on vectors, reservoirs, and clinical patterns of the disease; and moreover to guarantee access to therapeutic resources, including health registry, centralized purchasing of drugs through PAHO, and involvement of bilateral and multilateral international organizations in funding, in order to integrate economic aspects related to the epidemiological risk of Chagas disease.
The 5th Meeting in 2004 intended to analyze the epidemiological situation and the degree of progress of control programs, in order to reach agreement on work and recommendations to thus permit the Organization and other international cooperation agencies to better channel their policies and support to member countries. Present were governmental delegates from Ecuador, Peru and Venezuela, with invited experts from Argentina, Brazil, Colombia and Peru, with involvement from other institutions acting as observers and with technical assistance from the Latin American RELCOV network, the European Community project Chagas Disease Intervention Activities (CDIA,) and the Andean Health Agency "Hipólito Unanue" (CONHU). The meeting objectives were as follows:
The 6th Meeting in 2005 proposed tackling three main themes:
Other topics of general or focal interest can be addressed within such a basic conceptual framework, or other complementary ones, in the course of the development of activities during 2005–2006.
Approaches for integrated vector control (IVM) with environmental management and community participation should be a common instrument when performing these tasks.
The meeting encouraged horizontal cooperation among the IPA member countries and with other subregional Chagas initiatives.
It also promoted greater participation on the part of the scientific community, especially with regard to the research component, as a common vehicle to provide quality assurance for the activities undertaken.
A focus on interagency support based on participation by agencies, international organization and networks is yet another pillar of the development the subregion is reaching for, and which has already shown itself to be functioning well.