Progress towards interruption of transmission of Chagas disease.

Chagas disease, named after the Brazilian physician Carlos Chagas who first described it in 1909, exists only on the American Continent. It is caused by a flagellate protozoan parasite, Trypanosoma cruzi, transmitted to humans by triatomine insects. The geographical distribution extends from Mexico to the south of Argentina. The disease affects 1618 million people and some 120 million, i.e. about 25% of the population of Latin America is at risk of acquiring Chagas disease. There are two stages of the human disease: the acute stage which appears shortly after the infection and the chronic stage which appears after a silent period that may last several years. The lesions of the chronic phase irreversibly affect the autonomous nervous tissues of internal organs namely the heart, oesophagus and colon and the peripheral nervous system. After several years of an asymptomatic period, 27% of those infected develop cardiac lesions which may lead to sudden death, 6% develop digestive damage mainly megaviscera, and 3% will present peripheral nervous involvement. The risk of infection with Chagas disease is directly related to poverty: the blood-sucking triatomine bug which transmits the parasite finds a favourable habitat in crevices in the walls and roofs of poor houses in rural areas and in the peripheral urban slums. The rural/urban migration movements that occurred in Latin America in the 70’s and 80’s changed the traditional epidemiological pattern of Chagas disease and transformed it into an urban infection that can be transmitted by blood. The strategy for the interruption of vectorial and transfusional transmission of this disease is aimed at the prevention of new cases in children and young adults. The interruption of vectorial transmission is made through spraying the infested houses with insecticides. The interruption of transfusional transmission is achieved by screening blood samples in blood banks using serological techniques and discarding the infected ones.