Value of the antiglobulin test and indirect immunofluorescence test in the serological diagnosis of bovine brucellosis]

In investigations of 5881 sera from brucella infected herds and 8635 sera from negative herds the antiglobulin test (AgT) because of its high susceptibility was shown to be a valuable method in early diagnosis of brucellosis and clearing of non-specific LA-reactions. However, all infected animals are not detected with the AgT. Therefore it is not adaptable to use in selection controlling, also in combination with other methods. In the final steps of the eradication measures against bovine brucellosis the AgT offers a very valuable serological complementary method. The indirect fluorescence test has no diagnostical advantages in comparison with the AgT and is not recommended for practical brucellosis serology.     

The vaginal mucus agglutination test in the diagnosis of bovine brucellosis

Of 1140 vaginal mucus agglutination tests (VMAT) on specimens obtained in 1971-72 from 663 dairy cows in seven herds infected with brucellosis, 97 were positive. When the VMAT was positive one or more serological tests were also positive. Of the 97 corresponding serum agglutination tests 80 sera had titres of more than 533 international units. Only 69.8 per cent of VMAT from serologically positive cows were positive. No evidence was found of non-specific agglutinins in vaginal mucus and positive VMAT reactions appeared to be specific for field infection. Three cows showed evidence of local agglutinins in the vagina. Hence herd testing by VMAT has no advantage over tests of blood serum but the test could be an aid in establishing whether individual cattle are infected.     

Fluorescence polarization assay for the diagnosis of bovine brucellosis: adaptation to field use

A fluorescence polarization assay (FPA) was used to test whole blood samples prepared by mixing blood cells from cattle without exposure to Brucella abortus (B. abortus) with sera from animals with confirmed (bacteriologically) infection. A cut-off value between negative and positive values was initially established to be 87.2mP. This value was changed to 95mP to increase assay specificity without loss of sensitivity when testing blood samples from negative animals. The FPA technology was applied to whole blood samples in the field and to stored whole blood samples using two diluent buffers. Relative sensitivity and specificity values for the FPA performed in the field, based on buffered antigen plate agglutination test and competitive enzyme immunoassay results were 95.3 and 97.3%, respectively. However, to obtain maximum sensitivity and specificity, a cut-off value of 105mP was determined for fresh whole blood samples. The relative sensitivity and specificity values of the FPA when testing stored whole blood samples were 100% each using a 95mP cut-off.The usefulness of the FPA for testing whole blood samples in the field was demonstrated.     

Agglutination tests and their modifications in the diagnosis of bovine brucellosis

This article reviews the effects of using Yersinia enterocolitica serotype: 09 somatic antigen in diagnostic tests for brucellosis. The tests employed include the standard tube agglutination test, the microplate agglutination test, the quantitative plate agglutination test, the growth agglutination test and the indirect hemagglutination technique. Only the growth agglutination technique demonstrated an increased sensitivity over the STAT. Neither the microplate agglutination test nor quantitative plate tests offered any significant advantages over the STAT. The QPAT using Brucella O antigen was clearly subject to false negative results. The indirect hemagglutination technique showed extreme variation in results, the significance of which (if any) was unclear.     

Assessment of an intradermal test for the detection of bovine brucellosis

Forty-eight cattle were sensitised toBrucella antigens either by vaccination withBrucella abortus strain 19 (S19) orB. abortus 45/20 (S45/20) and 24 of these and 12 unvaccinated cattle were subsequently challenged with virulentB. abortus strain 544 (S544). All these cattle (n=60), together with 12 control cattle which were neither vaccinated nor challenged, were subsequently subjected to an intradermal test using a S45/20 protein antigen. Reactions were interpreted subjectively by observation and palpation and were measured to the nearest mm with calipers at 48 and 72 hours after injection of protein antigen. Ten weeks later the cattle were slaughtered and tissues cultured for the presence ofB. abortus. Two of the 48 vaccinated cattle died, 40 of the remaining 46 gave a positive response to the intradermal test at 48 hours and 36 were positive at 72 hours. In the controls any increase in the skin thickness had disappeared by 72 hours. An increase in skin thickness was still present at 72 hours in all other cattle except those vaccinated with S19 only. The intradermal test was found to be sensitive but not specific in detecting infected cattle and both sensitive and highly specific if used (with the exception of S19) to detect exposure toBrucella antigen.     

Validation of enzyme-linked immunosorbent assays for the diagnosis of bovine brucellosis

The purpose of this study was to evaluate the performance of the indirect enzyme immunoassay (IELISA) and the competitive enzyme immunoassay (CELISA) for the diagnosis of bovine brucellosis in comparison to conventional serological tests routinely used in Argentina. Serum samples (n = 3500), from Brucella-free herds, from vaccinated cattle and from naturally infected cattle, were tested by the following tests: buffered antigen agglutination test (BPAT), rose bengal test (RBT), 2-mercaptoethanol test (2-ME), complement fixation test (CFT), IELISA and CELISA. Sensitivity and specificity of the BPAT, RBT, IELISA and CELISA were determined relative to the 2-ME and the CFT. The CELISA was considered suitable for eliminating most serological reactions of vaccinated animals and was more specific than the other tests. The results indicate the potential use of the CELISA as a complementary assay in the brucellosis control and eradication program in Argentina and other countries, where Brucella abortusstrain 19 vaccination is mandatory.