[Prevalence of Trypanosoma cruzi infection in opossum (Didelphis albiventris) in Santiago del Estero, Argentina]. / Estudio de la prevalencia de la infección por Trypanosoma cruzi en zarigüeyas (Didelphis albiventris) en Santiago del Estero, Argentina.

The opossum of the genus Didelphis is one of the principal wild reservoirs of Trypanosoma cruzi and is widely distributed in the Western Hemisphere. Didelphis albiventris is the most common marsupial in Amamá and Trinidad, two communities in the province of Santiago del Estero, Argentina. The D. albiventris population is replaced every year, and the opossum normally has two reproductive periods, one at the beginning of the spring and another at the beginning of the summer. The two litters are weaned, and they leave the mother's marsupial pouch to join the population, the first (G1) at the beginning of the summer and the second (G2) at the beginning of the fall. Between 1988 and 1991 409 D. albiventris opossums were studied, and xenodiagnoses showed that 35% of them were infected with T. cruzi. Annual cycles of renewed infection were observed, with prevalences that ranged between 22% and 43%. The acquisition of the parasite occurred over the entire year, from the summer through the spring. The prevalence of infection increased with age. The G1 individuals tended to present higher prevalences than the G2 individuals, probably from being exposed to transmission for a longer period of time. In the first two (younger) age categories for the opossums, G2 individuals showed higher prevalences than did the G1 individuals. This indicates a significant increase in transmission intensity during the fall. Opossums should be regarded as a potential source of T. cruzi entry to the domestic transmission cycle.

Chagas disease in north-west Argentina: infected dogs as a risk factor for the domestic transmission of Trypanosoma cruzi.

The association between household seroreactivity to Trypanosoma cruzi in dogs and children and T. cruzi infection rates in domestic Triatoma infestans was investigated in 1988-1989 in the rural community of Amamá, north-west Argentina, where house spraying with residual pyrethroids was carried out in 1985. Three years after spraying, a greater reduction of the average T. cruzi prevalence rate in dogs (from 83% to 40%) than in children (from 48% to 30%) was accompanied by a substantial decrease in vector infection rates from 51%-63% to 21%. At a household level, in homes with or without seroreactive children, the percentage of infected T. infestans was 4.5-4.7 times higher when seroreactive dogs were present (27.1%-34.8%) than when they were not (5.8%-7.7%; stratified relative risk [RR] = 4.58). The contribution of seroreactive children to bug infection rates was not significant (RR = 1.29). The combined effect of both seroreactive dogs and seroreactive children fitted equally well with additive or multiplicative transmission models. Bug infection rates showed an increasing trend with the number of seroreactive dogs and an inverse association with the age of the youngest seroreactive dog. Our study supports the hypothesis of a causal association between the presence and number of infected dogs and increased levels of T. cruzi transmission to domestic T. infestans.

Dynamics of transmission of Trypanosoma cruzi in a rural area of Argentina. IV. Serologic, parasitologic and electrocardiographic study of the human population.

A serologic and electrocardiographic study was carried out in people living in 18 households in La Invernada (LI), Departamento Figueroa, and in 20 houses in Amamá (A), Departamento Moreno, both in the province of Santiago del Estero, Argentina. Serological tests performed were indirect hemagglutination (IHAT) and indirect immunofluorescence antibody tests (IFAT). Complement fixation, direct agglutination and ELISA tests were also done for those sera, showing discordant results for either IHAT or IFAT. All people in LI and children up to 12 years old in A were studied by xenodiagnosis. Approximately 50% of the whole population was infected (50% in LI and 50.9% in A) and a similar prevalence rate was already recorded in children below 10 years. A moderate increase of infection rates was observed in successively older age groups, indicating that most of the people became infected in the first decade of life. Comparison of serological profiles of both populations suggests a protective effect of insecticidal control campaigns in those individuals born between 1961 and 1971. New surveys carried out in both populations 2 years later rendered a 4 times greater annual incidence rate in A as compared with LI (7.9% vs 1.8% respectively). No differences were found in the percentages of abnormal electrocardiograms among seropositive and seronegative individuals from both settlements. The prevalence of complete right bundle branch block (RBBB) was higher in seropositive than in seronegative people (4.8% vs 2.3%) but lower than those figures recorded for other parts of the country and the continent. This suggests that in spite of its high prevalence, Chagas' disease has low morbidity in both localities.

Dynamics of transmission of Trypanosoma cruzi in a rural area of Argentina: IV. Serologic, parasitologic and electrocardiographic study of the human population

Se realizó un estudio epidemiológico y electrocardiográfico de los habitantes de La Invernada (LI), Depto. Figueroa, y de Amamá, Depto. Moreno, Pcia. Figueroa, y de Amamá, Depto. Moreno, Pcia. de Santiado del Estero. LI fue tratada con insecticidas en varias oportunidades durante las décadas del 60 y 70 mientras que Amamá no entró en la programación de las campañas de control. Todos los individuos de la vivienda fueron estudiados serológicamente por hemoaglutinación indirecta, e inmunofluorescencia indirecta, utilizándose fijación del complemento o aglutinación directa y Elisa para confirmar resultados discordantes. Se realizaron xenodiagnósticos a todas las personas en LI y a los menores de 13 años en Amamá. Los resultados indican que la mitad de la población estudiada estaba infectada con T. cruzi (50% en LI y en Amamá) y dichas prevalencias aparecieron ya en los niños menores de 10 años, notándose apenas un ligero incremento en la proporción de infectados en los siguientes grupos etarios. Se compararon los perfiles serológicos de ambas poblaciones destacándose el efecto protector de las campañas de control realizadas en LI sobre la población nacida entre 1961 y 1971. Una nueva encuesta serológica realizada dos años después en ambas poblaciones reveló que la tasa de incidencia anual fue 4 veces mayor en Amamá que en LI (7,9% vs. 1,8%). Los estudios electrocardiográficos no mostraron diferencias significativas entre individuos seropositivos y seronegativos en ambos caseríos en cuanto... (AU)

Dynamics of transmission of Trypanosoma cruzi in a rural area of Argentina: IV. Serologic, parasitologic and electrocardiographic study of the human population

Se realizó un estudio epidemiológico y electrocardiográfico de los habitantes de La Invernada (LI), Depto. Figueroa, y de Amamá, Depto. Moreno, Pcia. Figueroa, y de Amamá, Depto. Moreno, Pcia. de Santiado del Estero. LI fue tratada con insecticidas en varias oportunidades durante las décadas del 60 y 70 mientras que Amamá no entró en la programación de las campañas de control. Todos los individuos de la vivienda fueron estudiados serológicamente por hemoaglutinación indirecta, e inmunofluorescencia indirecta, utilizándose fijación del complemento o aglutinación directa y Elisa para confirmar resultados discordantes. Se realizaron xenodiagnósticos a todas las personas en LI y a los menores de 13 años en Amamá. Los resultados indican que la mitad de la población estudiada estaba infectada con T. cruzi (50% en LI y en Amamá) y dichas prevalencias aparecieron ya en los niños menores de 10 años, notándose apenas un ligero incremento en la proporción de infectados en los siguientes grupos etarios. Se compararon los perfiles serológicos de ambas poblaciones destacándose el efecto protector de las campañas de control realizadas en LI sobre la población nacida entre 1961 y 1971. Una nueva encuesta serológica realizada dos años después en ambas poblaciones reveló que la tasa de incidencia anual fue 4 veces mayor en Amamá que en LI (7,9% vs. 1,8%). Los estudios electrocardiográficos no mostraron diferencias significativas entre individuos seropositivos y seronegativos en ambos caseríos en cuanto...

Dynamics of transmission of Trypanosoma cruzi in a rural area of Argentina. IV. Serologic, parasitologic and electrocardiographic study of the human population.

A serologic and electrocardiographic study was carried out in people living in 18 households in La Invernada (LI), Departamento Figueroa, and in 20 houses in Amamá (A), Departamento Moreno, both in the province of Santiago del Estero, Argentina. Serological tests performed were indirect hemagglutination (IHAT) and indirect immunofluorescence antibody tests (IFAT). Complement fixation, direct agglutination and ELISA tests were also done for those sera, showing discordant results for either IHAT or IFAT. All people in LI and children up to 12 years old in A were studied by xenodiagnosis. Approximately 50

of the whole population was infected (50

in LI and 50.9

in A) and a similar prevalence rate was already recorded in children below 10 years. A moderate increase of infection rates was observed in successively older age groups, indicating that most of the people became infected in the first decade of life. Comparison of serological profiles of both populations suggests a protective effect of insecticidal control campaigns in those individuals born between 1961 and 1971. New surveys carried out in both populations 2 years later rendered a 4 times greater annual incidence rate in A as compared with LI (7.9

vs 1.8

respectively). No differences were found in the percentages of abnormal electrocardiograms among seropositive and seronegative individuals from both settlements. The prevalence of complete right bundle branch block (RBBB) was higher in seropositive than in seronegative people (4.8

vs 2.3

) but lower than those figures recorded for other parts of the country and the continent. This suggests that in spite of its high prevalence, Chagas disease has low morbidity in both localities.