Field trials of an improved cost-effective device for detecting peridomestic populations of Triatoma infestans (Hemiptera: Reduviidae) in rural Argentina

An improved device for detecting peridomestic Triatoma infestans consisting of one-liter recycled Tetra Brik milk boxes with a central structure was tested using a matched-pair study design in two rural areas in Argentina. In Olta (La Rioja), the boxes were installed beneath the thatched roofs and on the vertical wooden posts of each peridomestic structure. After a 5-month exposure, at least one of the recovered boxes detected 88 percent of the 24 T. infestans-positive sites, and 86 percent of the 7 negative sites by timed manual collections at baseline. In Amamá (Santiago del Estero), the boxes were paired with the best performing prototype tested before (shelter unit). After 3 months, some evidence of infestation was detected in 89 percent (boxes) and 79 percent (shelters) of 18-19 sites positive by timed collections, whereas 19 percent and 16 percent of 32 negative sites were positive, respectively. Neither device differed significantly in the qualitative or quantitative collection of every sign of infestation. The installation site did not modify significantly the boxes' sampling efficiency in both study areas. As the total cost of each box was half as expensive as each shelter unit, the boxes are thus the most cost-effective and easy-to-use tool for detecting peridomestic T. infestans currently available

Immunodiagnosis of Trypanosoma cruzi (Chagas' disease) infection in naturally infected dogs

This study reports on the standardization of an enzyme-linked immunosorbent assay (ELISA) for detecting specific antibodies anti-Trypanosoma cruzi in naturally infected dogs. Sera from 182 mongrel dogs of all ages residing in four rural villages in Santiago del Estero, Argentina, were collected in November 1994 and preserved in buffered neutral glycerin. All sera were tested by indirect hemagglutination test (IHAT), indirect immunofluorescence test (IFAT), and ELISA using the flagellar fraction of T. cruzi as antigen. Dog sera from an area without vectorial transmission were used to calculate ELISA specificity and cut-off-value. Eighty-six percent of sera had concordant results for all tests. All sera reactive for IHAT and IFAT were also rective for ELISA, except in one case. Sera tested by ELISA when diluted 1:200 allowed a clearer division between non-reative and reactive sera than when 1:100 with greater agreement among serologic techniques. The specificity of ELISA was 96,2 per cent. Among 34 adult dogs with a positive xenodiagnosis, sensitivity was 94 per cent both for ELISA and IFAT. ELISA is the first choice for screening purposes and one of the pair of techniques recommended for diagnostic studies in dog populations.

Standardization of serological tests for detecting anti-Trypanosoma cruzi antibodies in dogs

his paper reports on the standardization of four serological reactions currently used in human serodiagnosis for the detection of anti-Trypanosoma cruzi antibodies in naturally and experimentally infected dogs. Indirect immunofluorescence test (IFAT) and hemagglutination test (IHAT) were standardized, and complement fixation test (CFT) and direct agglutination test (DAT) were used for diagnostic confirmation. Four hundred and eighty one mongrel dogs that were studied by xenodiagnosis were used: (1) parasitemic dogs of two localities of endemic area (EA) of Santiago del Estero province in Argentina (n = 134); (2) non-parasitemic dogs of the same area (n = 285); (3) dogs experimentally infected with T. cruzi in the patent period (n = 6); (4) non-infected dogs (n = 56) which were born in the city of Buenos Aires (BA), one non-EA for Chagas' disease. For IFAT, parasitemic dogs EA showed 95 per cent of reactive sera. Non parasitemic dogs EA showed 77 per cent of non reactive sera. None sera from BA were reactive for dilutions higher than four. For IHAT, 84 per cent of sera of parasitemic dogs EA showed serological reactivity and among non parasitemic dogs BA, 61 per cent were non reactive, while the remainder showed at most titres of 1/16. The cut-off titres for IFAT and IHAT were 1/16 and 1/32 respectively, and for CFT and DAT 1/1 and 1/128 respectively. Sensitivity for IFAT, IHAT, CF and DAT were 95 per cent , 84 per cent , 97 per cent and 95 per cent respectively

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...