Vol. 17, No. 4	December 1996

Tripanosoma cruzi infection has been estimated to affect 16-18 million people in the Americas. At least 20% of these will develop the clinical symptoms that characterise Chagas disease. Approximately 43,000 deaths have been atributed annually to this disease. Although human infection extends from Mexico in the North to Argentina and Chile in the South, organized programs for the control of the vector of T. cruzi are being carried out mainly in the Southern Cone countries where the most important vector is the Triatoma infestans.

Vector control is done by a combination of spraying with residual insecticides, health education and, ocasionally, modification or replacement of housing.

Situation in the Southern Cone countries is as follows:

• Argentina reduced house infestation by 75% in 13 of the 15 endemic provinces between 1982 and 1994. During the same period the serological prevalence rate among men joining the military services decreased from 5.8% to 1.2%. More than 114,000 houses were sprayed in 1995. Interruption of transmission is foreseen for the year 2000.

• Bolivia is progressing more slowly. In spite of the above 26,800 houses were sprayed in 1995 (More than 400,000 houses still require spraying).

• Brazil reported that of the 711 municipalities infested with T.infestans in 1992, only 83 still remained positive in 1993. Intradomiciliary capture of infected insects for the whole country decreased from 84,000 bugs (1983) to 2500 (1993). In the States of Rio Grande do Sul and Bahia almost 200,000 houses were sprayed in 1995. Interruption of transmission is expected by the year 2000.

• Chile experienced a 90% reduction in house infestation rates from 1982 to 1993. In the endemic Region IV, seroprevalence rates among children less than 15 years old decreased from 20.3% in 1986 to 4.2% in 1992. However a portion of these cases are likely to represent congenital rather than vectorial infections. Interruption of transmission is expected by 1998.

• In Paraguay has just begun a coordinated effort to combat the vector: 32,502 houses were sprayed in 1995.

• Uruguay had a 90% reduction in house infestation rates. The rate of positive serology in children under 12 years old decreased from 5.2% in 1985 to 0.67% in 1994 in the departments of highest infestation such as Rivera, Paysandu, Tacuarembo, Cerro Largo, and Salto. Interruption of transmission is expected in 1997.

Source: Division of Disease Prevention and Control, Communicable Diseases Program,HCP/HCT, PAHO.

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