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ObjectiveTo study the risk of Trypanosoma cruzi domestic transmission using an entomological index and to explore its relationship with household's characteristics and cultural aspects. Methods There were studied 158 households in an endemic area in Argentina. Each household was classified according to an entomological risk indicator (number of risky bites/ human). A questionnaire was administered to evaluate risk factors among householders. ResultsInfested households showed a wide range of risk values (0 to 5 risky bites/human) with skewed distribution, a high frequency of lower values and few very high risk households. Of all collected Triatoma infestans, 44% had had human blood meals whereas 27% had had dogs or chickens blood meals. Having dogs and birds sharing room with humans increased the risk values. Tidy clean households had contributed significantly to lower risk values as a result of low vector density. The infested households showed a 24.3% correlation between time after insecticide application and the number of vectors. But there was no correlation between the time after insecticide application and T. infestans' infectivity. The statistical analysis showed a high correlation between current values of the entomological risk indicator and Trypanosoma cruzi seroprevalence in children. ConclusionsThe risk of T. cruzi domestic transmission assessed using an entomological index show a correlation with children seroprevalence for Chagas' disease and householders' habits. Resumen Objetivo

Thirteen communities from 7 Argentinian provinces were selected for the evaluation of serology as an indicator of transmission of Chagas disease. Of the communities appraised, 6 did not have a history of previous treatment with insecticides and 7 had received sporadic or continuous insecticide treatment. The inhabitants of 20% of the houses of each locality were studied by serology. The samples were obtained by finger pricking and 50 microliters of blood were mixed with 15 microliter of 50% glycerine solution in tissue culture media to be assayed by Indirect Hemagglutination and Indirect Immunofluorescence tests. In untreated areas, the prevalence of infection in infants 0-4 years old was 17.5%, reaching to over 22% for the 5-9 year old group, and to 33.3% in 10-14 year old individuals. The prevalence in treated and surveyed areas was 2.6% in 0-4 year old children, 5.4% in 5-9 year old and 6.2% in 10-14 year old youngsters. The differences between both areas were statistically significant (p less than 0.005). This study favors serology as a valid indicator for the evaluation of transmission of Chagas disease in rural areas.

SUMMARYThe population dynamics and the prevalence of chagasic infection of 352 dogs living in 108 rural houses infested by triatomines were studied. The region was divided into three sections according to increasing distances to an urban area. Each animal was identified by means of its particular characteristics and built, and its owners gave information about its habits. By means of xenodiagnosis, serology and ECG studies, prevalences of infection, parasitological-serological correlation, percentage of altered electrocardiographic outlines and percentage of houses with parasitemic dogs, were determined.The rural area showed a characteristic T. cruzi infection pattern and differences in the canine population parameters with respect to the other areas were observed: a higher proportion of puppies than adult dogs, a more sedentary population, higher prevalences of infection, as measured by xenodiagnosis, in dogs, and the highest proportion of bedroom insects infected with T. cruzi.It is assumed that the sedentary characteristics of the human population in that rural area impinge in the blood offer to the triatomine population, and the rúgh percentage of parasitemic dogs of the area, contribute to the rise of "kissing ougs" infected with T. cruzi found in bedrooms.

SYNOPSIS. Trypanosoma cruzi epimastigotes from cultures were separated into nuclear, mitochondrial, lysosomal, microsomal, and cell-sap fractions. Enzymic and ultrastructural controls served to determine the cleanness of separation. The bulk of the DNA was in the nuclear (78%) and mitochondrial (12%) fractions. RN'A was found in microsomal (74%) and cell-sap ( 14% ) fractions. Marker enzyme distribution (succinic dehydrogenase, acid phosphatase, and glucose-6-phosphatase) was compared with their distribution in mammalian tissues. Subcellular localization of antigens by Ouchterlony tests revealed 2 specific precipitin lines in cell sap and 1 in the microsomal fraction. These antigens may prove diagnostically and immunoprotectively valuable.