The elimination of Chagas' disease from Brazil

On 9 June 2006 the Pan American Health Organization (PAHO) presented the Minister of Health of Brazil with the International Elimination of Transmission of Chagas' Disease Certificate. This act was the culmination of an intensive process that began in 1991 with the Southern Cone Initiative, a joint agreement between the governments of Argentina, Bolivia, Brazil, Chile, Paraguay, Uruguay and Peru, to control Chagas' disease by the elimination of the main vector, Triatoma infestans. This initiative has been highly successful and the prevalence area of the vector diminished rapidly in the last years. As a consequence, the current seroprevalence in children aged between 0 and 5 years is of the order of 10(-5), a clear indication that transmission, if it is occurring, is only accidental. In this review I calculate the basic reproduction number, R0, for Chagas' disease and demonstrate that its relatively low value (1.25) explains why vectorial transmission was interrupted relatively easily. In addition, I used a mathematical model to forecast how long the remaining cases of the disease, as well as the additional vertically transmitted cases will last.     

Recent developments in the field of Chagas' disease

Chagas'' disease is an endemic human trypanosomiasis produced by Trypanosoma cruzi, which is usually transmitted by blood-sucking triatomid bugs. This article reports recent developments in research on Chagas'' disease and outlines some of the basic investigations that have immediate practical application or that contribute to our knowledge of the parasite and its relationship with the vertebrate host.     

A logistic regression model applied to Chagas' disease

The focus of this paper is the application of statistical models to the study of socioeconomic conditioning factors in perinatal Chagas' disease conducted in Rosario, Argentina. A case (154) and control (158) design was applied to investigate socioeconomic and cultural differences in pregnant women in Hospital Roque Sáenz Pe?a as to their infection status. Logistic regression models were used to evaluate the importance of antecedents linked to the infection and socioeconomic and cultural factors for infection status. For pregnant women, the importance of antecedents linked to the infection was confirmed and the women's level of schooling stood out as the predominant socioeconomic condition associated with infection. Log-linear models were used to explore the associations between certain explanatory variables. This approach pointed up the most relevant associations between such factors and Chagas' disease and provided a better understanding of the framework of relationships among them.     

An epidemiological approach to study congenital Chagas' disease

Transplacental transmission of Trypanosoma cruzi has been the focus of much attention in highly endemic areas in South America. Frequency of congenital transmission and factors associated with risk of it are still not well understood. Parasite strains may account for part of the geographical variation observed. Methodological differences between the studies do not permit a combined interpretation of results. This paper examines the epidemiological data available from Brazil, Bolivia, and Argentina and discusses possible epidemiological study design to investigate risk factors for transmission.     

Chagas' disease in the southern coastal region of Brazil

OBJECTIVE: To analyze serological data collected in two different periods, from the late 1960's to 1983, when these data was first added to the available information about vector triatomines found in the state of S?o Paulo, and from 1984 to 1999, a period when serology was used to describe endemic Chagas' disease in the state. METHODS: Serological surveillance data from schoolchildren (during the late 1960s and between 1973 and 1983), and the general population (between 1980 and 1982) of the municipalities of Cananéia, Iguape and Peruíbe were analyzed together with data collected on the vectors. RESULTS: Seropositivity among schoolchildren remained low and constant in the period from 1973 to 1982, and was no more detected in 1983. Cananéia showed titer distribution patterns typical of a non-endemic area, while Iguape and Peruíbe indicated low endemicity. Most of the cases came from other states; autochthonous cases were suggestive of oral transmission. There were reports of infestation by vector triatomines in 1,261 domiciliary units (main species: Panstrongylus megistus and Triatoma tibiamaculata). A total of 5,338 blood samples were collected and 40 were seropositive (0.75%). Triatomines captured within domiciles were mostly adults, and about half of them having fed upon human blood. Serological results of residents living in households where triatomines infected with Trypanosoma cruzi had been found did not differ from those living in houses infested only with non-infected insects. CONCLUSIONS: In addition to educational activities aimed at the local population, there is a need to develop a collaboration between scientific institutions to isolate and characterize trypanosoma strains from vectors, reservoirs (sylvatic or other) and humans. Thus, evolutional, ecological, pathological and other pertinent characteristics of different strains of such parasites could be better understood.