[en] The different serologic techniques for bovine brucellosis diagnosis have different abilities to detect antibodies after vaccination with Brucella abortus strain 19. The humoral response in heifers vaccinated with Brucella abortus strain 19 was evaluated by using several serologic techniques. In the experimental field of INTA, Pilcaniyeu, Rio Negro province, sixteen 5 months old heifers were vaccinated subcutaneously with a standard dose (2ml, containing 20x10⁹ to 10x10⁹ living organisms) of Brucella abortus strain 19. Sera from all the heifers were obtained on 18 occasions (one 87 days before vaccination, one immediately before vaccination and on 16 occasions after vaccination, during 488 days) and analyzed by buffered plate antigen test, rose bengal test, standard tube agglutination test, 2-mercaptoetanol test, complement fixation test, indirect ELISA, and competitive ELISA. Prior vaccination, 100% of the heifers gave negative results in all the techniques used, while 100% of them gave positive reaction in the first sampling after vaccination to all the techniques, with the exception of standard tube agglutination test that showed agglutinating titters of 1/100 or higher (positive threshold) in only 71.4% of the heifers. The indirect ELISA technique showed a reducing percentage of positive animals up until 316 days after vaccination, after which positive results were obtained. The competitive ELISA gave positive results in a variable number of heifers up to 253 days after vaccination when 100% of the sera were negative to this technique. Buffered plate antigen test was the technique that gave positive results for a longest period, being 100% of the animals negative to this technique at 450 days after vaccination. The other serological techniques assayed gave positive results during variable periods of time, intermediate between standard tube agglutination test and buffered plate antigen test. Although the present results were obtained from a limited number of animals, they clearly show that the diagnosis of bovine brucellosis in animals older than 18 months, with the technique used here is not interfered by the residual antibodies after vaccination with strain 19 at 5 months of age. (author)

[en] A variety of newer diagnostic procedures based around the use of molecular technologies are now being undertaken to further characterise the foot-and-mouth disease (FMD) virus enabling a deeper understanding to be gained of the pathogenesis and epidemiology of this disease. Such approaches have categorically identified the carrier state and highlighted the importance of carrier animals in control programmes. Use of the polymerase chain reaction provides even further insight into the carrier animal but interpretation of data has to be undertaken with caution. The role of non-structural proteins can provide further insight into an animals response to both vaccination and natural infection and could provide a basis for separation of the carrier state. Finally the pivotal role of monoclonal antibodies in all aspects of FMD research is now clear and these highly specific reagents are now being used for a variety of research and diagnostic purposes within the FMD field. (author)

[en] Foot-and-mouth disease (FMD) virus is characterised by its rapid transmission and its great antigenic variability which require a requires a rapid and accurate diagnosis in the laboratory, in order to initiate an immediate response for control. From these studies it is clear that Enzyme linked immunosorbent assay (ELISA) has the advantage over the Complement fixation test (CFT) of being a test of high sensitivity and specificity. Therefore, this technique is now used in our laboratory for diagnosis to detect FMD virus (O-A-C) in epithelia from animals affected by the disease. (author)

[en] The objective of this study was to undertake an interlaboratory comparison of a liquid phase blocking ELISA for detection of antibodies to FMD virus. For that purpose sera from 120 vaccinated, 120 infected and 120 FMD negative cattle were tested. All sera were tested in a screening assay at a dilution of 1/32. Positive sera were tested in a titration assay (1/10, 1/50, 1/250, 1/1250). For serotype O₁ Cruzeiro 108 sera from the FMD-free group were classified as negatives giving a specificity of 90%. For the same serotype the group of infected/vaccinated cattle gave 114/115 positive results showing a sensitivity of 95% respectively 96%. For serotype A₂₄ Cruzeiro from the FMD-free group 85 sera were classified as negatives giving a specificity 71%. For the same serotype the group of infected/vaccinated cattle gave 90/99 positive results showing a sensitivity of 75% respectively 82%. The predictive value of the assay was good as results expected for the different serum categories were mainly confirmed in the test. Nevertheless a high number of plates were rejected due to 'outside limits' and further adjustments are necessary to obtain more reliable results. (author)

[en] In 1986 the Animal Production and Health Section of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture embarked on a programme of support to scientists in developing countries focused on improving animal disease diagnosis through the use of nuclear and related technologies. As part of this programme the Swedish International Development Authority (SIDA) agreed to provide support for a FAO/IAEA Co-ordinated Research Project (CRP) concerned with the introduction and use of such technologies in Latin America. Through this programme, which was entitled Regional Network for Latin America on Animal Disease Diagnosis Using Immunoassays and Labeled DNA Probe Techniques, studies were supported on a number of diseases considered to be of substantial economic and social importance to the region, including brucellosis, tuberculosis, babesiosis, leukosis, bluetongue and chlamydia infection in cattle and psedorabies in pigs. One significant conclusion was that large number of diseases studied limited research findings owing to the lack of a critical mass of scientists studying any one specific disease problem. Thus when in 1991, SIDA agreed to follow-up CRP on Immunoassay Methods for the Diagnosis and Epidemiology of Animal Diseases in Latin America, the work was restricted to three diseases, i.e. foot-and-mouth disease (FMD), bovine brucellosis and bovine babesiosis. In 1994 results were presented in Guadeloupe, Lesser Antilles, France. The outcome of this meeting was the validation of ELISAs for the above mentioned diseases and a recommendation that future research should focus on diagnosis and epidemiology to support existing control and eradication campaigns against the two diseases of major importance in the region (FMD and Brucellosis). A follow-up CRP (1994-1997) entitled the Use of ELISA for Epidemiology and Control of Foot-and-Mouth Disease and Bovine Brucellosis in Latin America focused on the further validation and subsequent use of a competitive brucellosis ELISA and a FMD antibody liquid phase blocking ELISA. This TECDOC records the scientific achievements (39 papers) of these last two research projects (1991-1997) in a number of countries in Latin America. The report details the validation of standardized assays for the three diseases studied and recounts national surveys and their implications. Closely related to national or regional animal health campaigns these efforts are expected to have a sustainable impact not only on health and production but also on improvement of international trade of livestock in Latin America. The expected eradication of FMD and brucellosis from the continent by the year 2009 from the majority of countries can be considered as milestones in that process

[en] As part of a tick-borne disease control programme in the Lesser Antilles, studies were undertaken to determine the prevalence of cowdriosis, babesiosis and anaplasmosis in an effort to determine what the impact of tick eradication would be. The epidemiological situation for bovine babesiosis and anaplasmosis is unstable in all the islands of the Lesser Antilles, but the clinical cases are only recorded in imported breeds, which represent less than 5% of the cattle population. The native cattle population react as if naturally resistant. When the A. variegatum tick eradication campaign begins, it will be necessary, by the end of the acaricide treatment regime, to immunize all the imported cattle born during that period, and possibly all of the seronegative imported cattle already on the islands. Both Antigua and Guadeloupe have a long history of infestation with the tick and both have experienced clinical cases of cowdriosis. On the other islands, less than 6% of the sera were positive and this correlates well also with an apparent absence of clinical cases of cowdriosis. (author)

[en] A serum bank of 1251 adult cows sera was prepared. The sera originated from animals of three different epidemiological groups: 1) 244 from infected cows, strain 19 vaccinated when calves; 2) 507 from herds free of infection but all cows were strain 19 vaccinated when calves and 3) the last group, 500 sera from cows free of infection and non-vaccinated. All the sera where tested with the routine Rose Bengal (RB) Rivanol (RIV) and Complement Fixation (CF) tests and additionally three enzyme immunoassays were performed. They included two indirect Elisa both using the kit from the Joint FAO/IAEA Division, Vienna, Austria. One assay used a polyclonal conjugated antibody (I-ELISAp) and the other a monoclonal conjugated antibody (I-ELISAm). The third assay was a competitive ELISA (C-ELISA) performed with sLPS, plus monoclonal antibody, M84, and goat anti-mouse antibody-HRPO. Using the CFT as 'gold standard' the sensitivities of all the methods were: RB 87.1%, RIV 87.1%, I-ELISAp 100% I-ELISAm 100%. The calculated specificity was: RB 100%, RIV 100%, I-ELISAp 96.4% and I-ELISAm 100%. In the group of infected animals (244) the following results were obtained: RB 13.5%, RIV 11.9%, CF 12.7%, I-ELISAp 50.8% and I-ELISAm 22.9%. Results for the non-vaccinated group were: RB 0.2%, RIV 0%, CFT 0.2%, I-ELISAp 6.9% and I-ELISAm 2.9%. The C-ELISA was performed on samples from the positive group or with positivity values close to the cut-off value in the I-ELISAm. In the infected group 28 out of 63 animals were detected as infected and from the non-vaccinated herds none of 15 I-ELISAm positive samples were detected as infected in the C-ELISA. (author)

[en] The ELISA kit provided by the FAO/IAEA for the diagnosis of Babesia bovis was validated. In order to determine the appropriate ELISA cut-off point that would serve as the threshold between positive and negative samples, 119 serum samples from a Mexican Babesia-free zone were analyzed. The optimal cut-off point chosen was at 12% of the reactivity of the high positive control serum sample (PP) which resulted in a specificity of 97%. One hundred and ninety-six cattle from Wisconsin, USA, were introduced into Yucatan, Mexico, of which 181 were vaccinated with an attenuated live Babesia bovis vaccine; 15 animals remained as unvaccinated controls. Before and after vaccination all animals were bled and tested by enzyme linked immunosorbent assay (ELISA) and indirect fluorescence antibody test (IFAT). Both tests showed a high degree of correlation in their results. To evaluate an immune response to vaccination the optimal cut-off point chosen was 12% PP resulting in a sensitivity 99% and a specificity 95%. We concluded that the ELISA test has proved to be useful in Yucatan, Mexico for serological surveys and monitoring the efficiency o vaccination programmes. (author)

[en] An enzyme linked immunosorbent assay (ELISA) kit for detect antibodies to Babesia bovis, an intraerytrocitic bovine parasite was evaluated using known negative and positive samples and the results were compared with an indirect immunofluorescent antibody test (IFAT). Results obtained with field samples were used to estimate seroprevalence of B. bovis in an endemic area to the cattle tick (Boophilus microplus) vector of bovine babesiosis. Percentage of positivity (PP) values (optical density of tested serum/mean optical density of positive control) on 274 negative samples, had major values ranged in the frequency of 4.0 to 7.0 PP. Comparison between ELISA and IFAT showed an agreement of 93.3% on field sera samples, collected in areas of low, good and high soil fertility in the region of Bage (31 degree 20 min 13 sec S, 54 degree 06 min 21 sec W), RS, Brazil. From 5,082 tested sera, 3,751 (73%) were positive for B. bovis antibodies. No significant difference (P>0.05) was observed between results from calves living in areas of low and good soil fertility (80 and 82% of seroprevalence, respectively). However, calves living in soil of high fertility showed a minor inoculation rate for B. bovis (63% of seroprevalence), indicating needs of measures to prevent losses due to babesiosis. (author)

[en] In order to contribute to the definition of the best ELISA test for screening and differential diagnosis of Brucella abortus to be applied for control programmes, a total of 2971 sera from Colombian cattle were tested for brucellosis. Conventional agglutination tests, Buffered Plate antigen test (BPAT) and Rose Bengal (RB) as well as Complement Fixation test (CFT) (Alton, et al. 1988) were used comparatively. Radial immunodiffusion test (RID) was also performed to all sera. The sera were also tested using four different ELISAs: indirect ELISA from FAO/IAEA and the indirect ELISA modified by Nielsen, et al. 1992 as well as two competitive ELISAs: one competitive ELISA used B. abortus O-polysaccharide antigen and an enzyme conjugated monoclonal to the O-polysaccharide for competition and detection. The second competitive ELISA used lipopolysaccharide (sLPS) antigen, a different monoclonal antibody for competition but also specific for the O-polysaccharide and a commercially available goat anti-mouse IgG enzyme conjugate for detection. The sera were analyzed based on its population status, 987 positive obtained from Brucella abortus infected herds based on clinical and/or bacteriological evidence and a high prevalence of brucellosis, CFT percentage of positive animals in the herd was greater than 5%. Eight hundred sixty six (866) negative sera from non-vaccinated cattle from a brucellosis free area and 1118 negative sera obtained from reglamentary vaccinated areas under a free herd program. Initial cut-off values were derived using negative serum samples. The diagnostic sensitivity and specificity was defined from frequency histograms based on this cut-off values and using 2x2 tables, corresponding confidence limits (95%) were calculated. The data were also analysed using signal detection analysis (ROC). Kappa statistics was determined for all tests and populations, accuracy was used as index of comparison to evaluate different assays. The data support the initial hypothesis that the ELISA methodology designed for brucellosis will provide more precise and standardised method for diagnosis and for the support of control and eradication campaigns. (author)