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