Control of the transmission of Trypanosoma cruzi in Argentina 1999.

Approximately 2 million people in Argentina are infected with Trypanosoma c ruzi,the etiologic agent of Chagas disease, thereby constituting the major tropical disease in the country. As in other six Southern Cone countries, T riatoma infestans is the only or major vector of T. cruzi among human and d omestic animals. In Argentina, a vertically structured National Chagas Cont rol Program was established in 1962. Such a program pursued the elimination of domestic and peridomestic populations of T. infestans through insectici dal spraying, and the serological control of blood donors to prevent transf usion-related infections. This program strongly reduced the nation-wide ser ological prevalence of T. cruzi in the population. For example, in 18 or 20 year-old men drafted into military service, the seroprevalence decreased f rom 10.1% in 1964 for those who had been born in 1944 to 1.9% in 1993 for t hose born in 1975. However, the vertical strategy failed to reach and susta in the surveillance phase in widespread rural areas with disperse populatio ns due to its intrinsic limitations and the reduced priority level assigned to rural health programs. An alternative, horizontally-structured control strategy of T. infestans was developed and assayed in the Province of Santi ago del Estero between 1985-1989, and 1991-1992. The projects demonstrated that insecticidal spraying carried out with community participation combine d effectiveness and commitment in such a way as to produce a strong impact on house reinfestation and the extension of the area under entomological su rveillance. This experience has been transferred in a chain of responsibili ties to the personnel of the National Chagas Control Program, using partici pating workshops, procedural guidelines, and practical training. This perso nnel transferred the strategy using similar methods to the field health car e agents and volunteers chosen by their own communities (community leaders) . After the workshops, the leaders received all the materials needed to ins tall and develop the ongoing surveillance activities: third generation pyre throid insecticides, manuals, hand-operated sprayers, and sensor boxes to d etect domiciliary infestations. From 1993 to 1998, a total of 15,000 health care agents or community leaders were trained. A total of 675,000 houses w ere sprayed with residual insecticides in the attack phase, and 850,000 hou ses entered the surveillance phase. This is the first time that such large coverage has been accomplished in Argentina. The network of laboratories in stalled a quality assurance program to current serological procedures appli ed to blood donors, organ transplant, and the detection and treatment of ne w-borns to women seroreactive for T. cruzi in Argentina. We expect to inter rupt the vector-mediated transmission of T. cruzi in the next 18 months, bu t the sustainability of such a program depends on, at least, additional wor k with the community to achieve a change of attitudes and practices related to house infestation for the next 10 years. A social effort will be needed to cover those expenses, but the expected economic returns exceed largely the cost of any such program, as suggested by cost-benefit studies. To illu strate, the annual treatment costs of one Chagas patient can help maintain 25 households free from triatomine bugs in Argentina.