ABSTRACT
Flight activity and invasion of houses by Triatoma sordida and T. guasayana were studied in the Province of Santiago del Estero, Argentina. Spontaneous findings of both species in houses were recorded from 1982 to 1989. Light trap collections were performed in 1982, 1983 and 1984, at the woods surrounding the settlements of Amamá (43 houses) and Trinidad (19 houses). Most of the 101 triatomines collected, were unfed and negative for Trypanosoma cruzi. T. guasayana predominated over T. sordida, and both appeared on the lighted screens between 19-31 min (mean 24) after dusk and the catch time was 30-45 min. Although entomological evaluation of 41 houses at Amamá performed in September 1985, just before insecticidal spraying, showed that Triatoma infestans predominated, adults of T. guasayana were collected in sleeping places, in 7 houses (17%). Most triatomines invading houses from then up to 1990 were flying T. guasayana (20/27) and females outnumbered males. Three non-infected T. guasayana females were fed on man and two T. guasayana males positive for "T. cruzi like" trypanosomes were unfed. Therefore, visiting hungry adults could transmit T. cruzi to people and introduce wild parasites to the domestic cycle. T. guasayana stands as the main potential substitute of T. infestans in the studied area, and it might play there the same role as T. sordida in Brazil.
Subject(s)
Behavior, Animal , Triatoma/physiology , Animals , Argentina , Female , Male , Triatoma/growth & developmentABSTRACT
The daily probability (P) of transmission of Trypanosoma cruzi to a noninfected human host by an infected Triatoma infestans bug was estimated using field data from a 2-year longitudinal study carried out in a rural settlement of 20 households in Amamá, Santiago del Estero, Argentina. The following information was used for this purpose: the bug density and the proportion of infected bugs; the bug biting rate and the distribution of bites between humans and animals; the age-specific seropositivity to T. cruzi of the human population; and the actual number of new cases of human infection. The 2-year accumulated number of infective contacts per house estimated using a binomial model shows a statistically significant logistic correlation with the observed proportion of new cases per house. An average house where new cases of human infection were registered in the 2-year period had a P value of 0.0012, while an average general house (i.e., with and without new cases) had a P value of 0.0009. The observed range of P is discussed in terms of the chain of factors that affects the individual human risk of acquiring the infection and the possible entomological sampling errors.
Subject(s)
Chagas Disease/transmission , Triatoma/parasitology , Adolescent , Animals , Argentina/epidemiology , Chagas Disease/epidemiology , Child , Child, Preschool , Humans , Infant , Insect Bites and Stings , Insect Vectors , Longitudinal Studies , Models, Biological , Population Density , Probability , Rural PopulationABSTRACT
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.
Subject(s)
Chagas Disease/epidemiology , Adolescent , Adult , Argentina/epidemiology , Chagas Disease/diagnosis , Chagas Disease/transmission , Child , Child, Preschool , Electrocardiography , Female , Humans , Incidence , Infant , Male , Middle Aged , Rural Health , Serologic Tests/methodsABSTRACT
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.
