A comparison of standard serological tests for the diagnosis of bovine brucellosis in Canada.

Six agglutination and two complement fixation tests were compared with respect to specificity, sensitivity and relative sensitivity for the serodiagnosis of bovine brucellosis. Based on 1051 sera from brucellosis free herds, the specificity of the tests was 98.9% for the buffered plate antigen test (BPAT), 99.2% and 99.3% for the standard tube and plate agglutination tests (STAT and SPAT), respectively, and 99.8% for the 2-mercaptoethanol test (2MET). On this small sample, the rose bengal plate test (RBPT), card test (CARD) and the complement fixation test (CFT) correctly classed all sera as negative. On a sample of 167 culture positive cattle, the sensitivities of the tests were CFT: 79.0%, BPAT: 75.4, RBPT: 74.9%, CARD: 74.3%, SPAT: 73.1%, STAT: 68.9%, and 2MET: 59.9%. All tests combined detected only 82% of these infected cattle. Analysis of the relative sensitivity of the six agglutination tests gave the following ranking: BPAT greater than RBPT greater than CARD greater than SPAT greater than STAT. The 2MET ranked between the BPAT and RBPT or between the RBPT and CARD depending on the analysis used. The use of the BPAT as a screening test is recommended provided that a test of high specificity and sensitivity such as the CFT is used to confirm screening test reactions.     

An evaluation of the delayed-type hypersensitivity test for diagnosing brucellosis in individual cattle: a field study

A field study was conducted to evaluate the delayed-type hypersensitivity (DTH) test in diagnosing brucellosis in cattle, in particular the diagnosis of infection in individual cows. A total of 93 cows that were negative, suspect, or positive to the serum agglutination test (SAT), complement fixation test (CFT), or the milk ring test (MRT) were subjected to the DTH test. The cows were then slaughtered and the supramammary lymph nodes were collected for bacteriologic examination. In 989 cows the DTH test, MRT and serologic tests were negative. When the DTH test results were compared with bacteriologic results, 12 of the 93 cows with CFT titres greater than 1:200 tested negative in the DTH test while bacteriologic results were positive. The sensitivity of the DTH test (calculated on the remaining 81 cows) was 100%; the specificity was 83%. The sensitivity of the DTH test (calculated on 93 cows) was 81%; the specificity was 83%. The sensitivity and specificity of the DTH test correlated well with those of the CFT (86-83%). We conclude that the DTH test is very sensitive, and specific enough to diagnose brucellosis in individual cows. The DTH test should be used in combination with serologic tests in the diagnosis of brucellosis.     

Serological crossreactivity between Brucella abortus and Yersinia enterocolitica 0:9 III. Specificity of the in vitro antigen-specific gamma interferon test for bovine brucellosis diagnosis in experimentally Yersinia enterocolitica 0:9-infected cattle

The course of immunological reaction in 10 Yersinia enterocolitica 0:9 experimentally-infected heifers was followed using the conventional brucellosis tests complement fixation test (CFT), serum agglutination test (SAT) and brucella card test (BCT), and a recently developed Brucella antigen-specific gamma interferon (IFN-γ) test. Initially, the animals were exposed orally to 10¹⁰ colony-forming units (CFU) of Y. enterocolitica 0:9. Four weeks later, they were inoculated intravenously with 10⁸ CFU of Y. enterocolitica 0:9 cells. After oral inoculation, the response in the conventional brucellosis tests was minimal. Only after intravenous inoculation were CFT and SAT titres and BCT reactions comparable to natural, false positive brucellosis reactors. After oral exposure the Brucellergen-stimulated release of IFN-γ peaked at values above the cut-off stimulation index of 2.5 in 80% of the heifers. After intravenous inoculation, stimulation indices above 2.5 were present in only 10% of the animals. Two B. abortus infected control cattle showed stimulation indices of 3.1 and 3.4, and a negative control animal exhibited a stimulation index of 1.0. These findings show, in contrast to a previous study, that the Brucellergen-specific IFN-γ assay cannot be used as a specific and discriminatory test for B. abortus infections.     

How to substantiate eradication of bovine brucellosis when aspecific serological reactions occur in the course of brucellosis testing

Collaborative work was financed by the EU to develop and assess new diagnostic tools that can differentiate between bovine brucellosis and bovine infections due to Yersinia enterocolitica O:9 either in conjunction with, or as an alternative to, the classical serological, bacteriological or allergic skin tests. Sixteen heifers were experimentally infected with Brucella abortus biovar 1 (five heifers), Brucella suis biovar 2 (two heifers), Y. enterocolitica O:9 (six heifers) and Y. enterocolitica O:3 (three heifers). Four heifers, naturally infected with Y. enterocolitica O:9 that presented aspecific brucellosis serological reactions were also included in the experiment. A self-limited infection was induced in cattle by B. suis biovar 2. All the brucellosis serological tests used, i.e. the slow agglutination test (SAW), the Rose Bengal test (RB), the complement fixation test (CFT), indirect and competitive ELISA’s, lacked specificity when used to analyze sera from Y. enterocolitica O:9 infected animals. A Yersinia outer membrane proteins (YOPs)-ELISA was also used and although the test is able to detect a Yersinia group infection, it provided no evidence of whether or not there is a possible brucellosis infection when dual infections are present. The brucellergen IFN-γ test showed a lack of specificity also. The only test that was proven to be specific is the brucellergen skin test. All brucellosis serological tests, except the indirect ELISA, were limited in their ability to detect B. abortus persistently infected animals.

Based on these experimental studies, a strategy was implemented as part of the year 2001 Belgian Brucellosis Eradication Program to substantiate the eradication of bovine brucellosis. Epidemiological inquiries have identified risk factors associated with aspecific serological reactions, possible transmission and infection of cattle by B. suis biovar 2 from infected wild boars; and both legal and administrative measures taken by the veterinary services. No cases of bovine brucellosis have been confirmed in Belgium since March 2000.     

The first report in new zealand of Lymnaea columella say (Mollusca: gastropoda) an intermediate host of the liver fluke Fasciola hepatica L

Six herds of dairy cattle, in which infection had persisted after measures had been employed to eradicate brucellosis, were investigated in detail. One hundred and two animals out of 700 (14.6%) had evidence of the disease from cultural or serological tests. Only 4 infected animals aborted; the remaining 98 animals with brucellosis exhibited no clinical sign of the disease, and 52 were heifers calving for the first time. Sixty-five of the 700 animals (9.3%) produced brucella-infected vaginal discharges at the end of a normal period of gestation, and another 17 (2.4%) were detected only by the brucellosis (Brewer) card test (BCT) or complement fixation test (CFT). All the infected animals were removed from the herds immediately after detection.

About 2 weeks after all the cows had calved, 20 of the remain-ing 510 animals (3.9%) in 4 of the herds became positive to one or more tests and 8 excreted brucellae in their milk. The pregnancy of three 2-year-old primiparous heifers terminated normally and one aborted. All four discharged brucellae until they were slaughtered 20 to 35 days after parturition.

Twenty-five of the 102 infected animals were detected by bacteriological, and 29 by serological, means only. A compari-son was made of the results of the testsfrom 73 culturally positive animals; 4.1% of the sera were CFT positive but BCT negative, and 5.5% were BCT positive but CFT negative. An attempt has been made to explain the large numbers (34.2%) of infected animals that were serologically negative.     

Infection of cattle with Brucella abortus biovar 1 isolated from a bison in Wood Buffalo National Park.

An experiment was conducted to determine if cattle could be infected with a strain of Brucella abortus biovar 1 isolated from a bison in Wood Buffalo National Park. Three pregnant cows inoculated conjunctivally with 5.7 x 10(8) cfu of the bacterium, and their subsequent calves, showed seroconversion on standard serological tests for bovine brucellosis, and large numbers of the bacterium were isolated from numerous tissues at necropsy. A 4th cow that was moved into the pen that previously contained the inoculated cows subsequently showed seroconversion, and the same strain of B. abortus biovar 1 was isolated from numerous tissues. Although this strain from bison in Wood Buffalo National Park has existed in isolation from cattle for over 60 years, it remains infectious and contagious for cattle.     

Comparison of serologic tests for detection of Brucella infections in cattle and water buffalo (Bubalus bubalis)

OBJECTIVE: To estimate sensitivity and specificity of 4 commonly used brucellosis screening tests in cattle and domestic water buffalo of Trinidad, and to compare test parameter estimates between cattle and water buffalo. ANIMALS: 391 cattle and 381 water buffalo. PROCEDURE: 4 Brucella-infected herds (2 cattle and 2 water buffalo) and 4 herds (2 of each species) considered to be brucellosis-free were selected. A minimum of 100 animals, or all animals > 1 year of age, were tested from each herd. Serum samples were evaluated for Brucella-specific antibodies by use of standard plate agglutination test (SPAT), card test (CT), buffered plate agglutination test (BPAT), and standard tube agglutination test (STAT). A Bayesian approach was used to estimate sensitivity and specificity of diagnostic tests without the use of a gold standard, assuming conditional independence of tests. RESULTS: Sensitivity and specificity estimates in cattle, respectively, were SPAT, 66.7 and 98.9; CT, 72.7 and 99.6; BPAT, 88.1 and 98.1; and STAT, 80.2 and 99.3. Corresponding test estimates in water buffalo, respectively, were SPAT, 51.4 and 99.3; CT, 90.4 and 99.4; BPAT, 96.3 and 90.7; and STAT, 75.0 and 98.8. Sensitivity of the CT and specificity of the BPAT were different between cattle and water buffalo with at least 95% probability. CONCLUSIONS AND CLINICAL RELEVANCE: Brucellosis serologic test performance varied by species tested, but BPAT had the highest sensitivity for screening cattle and water buffalo. Sensitivity and specificity of more than 2 screening tests can be estimated simultaneously without a gold standard by use of Bayesian techniques.     

Evaluation of an enzyme-labeled antiglobulin test for anti-Brucella immunoglobulin G among 3 cattle populations

Antibody to smooth Brucella abortus lipopolysaccharide antigen on the surface of polystyrene tubes was detected with peroxidase-labeled antibody against bovine immunoglobulin G. The enzyme-labeled antiglobulin test (ELAT) activity of samples was expressed in arbitrary units/0.01 ml by reference to a standard curve based on tests of dilutions of a positive serum pool. Reactions greater than 3.0 U/0.01 ml were classified positive because specificity at this level was 99.8% (417/418 samples correctly classified negative) with agglutination test-negative sera from 33 Brucella-free herds. Results of the ELAT were compared with results of agglutination tests and the complement-fixation test (CFT), using 430 sera from cattle in 7 infected herds. Activity of greater than 5.0 ELAT U/0.01 ml was detected in all 54 sera classified as positive (titer greater than 1:10) by the CFT, including 5 sera classified as negative by the tube agglutination test. Sera from 8 nonvaccinated cows in the infected herds reacted only by the ELAT, whereas reactions were obtained with 25 and 5 sera by only agglutination tests and the CFT, respectively. The ELAT and CFT results were in agreement for 25 of 26 sera from agglutination test-reactor cattle in herds of unknown status. Comparisons of milk ring and whey agglutination tests with the whey ELAT on 146 quarter samples from cows in an infected herd revealed no ELAT activity greater than or equal to 1.0 U/0.01 ml in the 73 samples considered negative by the 2 other tests. Samples (n = 47) that contained greater than or equal to 1.0 ELAT U/0.01 ml included all (n = 40) samples with milk ring or whey agglutination titers greater than or equal to 1:16 and greater than or equal to 32, respectively, and 7 samples that gave weaker reactions to the latter tests.     

The use of skin delayed-type hypersensitivity as an adjunct test to diagnose brucellosis in cattle: a review

Brucellosis, caused by bacteria of the genus Brucella, is a contagious disease that causes economic loss to owners of domestic animals due to loss of progeny and milk yield. Because cattle, sheep, goats, and to a lesser extent pigs are considered to be the source of human brucellosis, serological tests have been used to screen domestic animals for antibodies against Brucella. Although the serological tests helped to eradicate brucellosis in many countries, serological tests are not always adequate to detect latent carriers of Brucella. Therefore, the use of the skin delayed-type hypersensitivity (SDTH) test, which is independent of circulating antibodies, might improve the diagnosis of brucellosis. In the literature, however, there are conflicting reports as to the value of the SDTH test for the diagnosis of brucellosis. Some studies consider the test unreliable, whereas others advocate its use because it detects brucellosis earlier than serological tests. The objectives of this study were therefore to assess the characteristics of the SDTH test, to select a Brucella strain that will yield a suitable brucellin for use in the field, and to determine whether the use of serological tests in combination with the SDTH test improves the detection of brucellosis. The results of this study clearly show that the SDTH test detects latent carriers of Brucella and confirms brucellosis in cattle with ambiguous serological test results. Brucellins prepared from smooth or mucoid strains of Brucella are better suited for use in the field than brucellins prepared from rough strains because they detect brucellosis in cattle with acute as well as chronic infection. The SDTH test is highly specific (99.3% specificity), and repeated testing of naive cattle or cattle infected with microorganisms that serologically cross-react with Brucella does not sensitize cattle to subsequent SDTH tests. However, it is possible that some naive cattle may serologically react to the injection of brucellin. The effect of these serological reactions on the sero-diagnosis of brucellosis is limited, because cattle may only now and then react serologically either with the serum agglutination test (SAT) or the complement fixation test (CFT). Nevertheless, cattle infected with microorganisms that serologically cross-react with Brucella may test seropositive for brucellosis 4 to 7 weeks after injection of brucellin, depending on the cross-reacting microorganism. The value of the SDTH test for the diagnosis of brucellosis was demonstrated after an outbreak of brucellosis. When the SDTH test was used in combination with SAT and CFT at diagnostic threshold > or =2 mm or > or =1 mm (increase in skinfold thickness), respectively, 39/44 (88%) or 42/44 (95%) of the infected cattle were detected compared with only 27/44 (61%) when SAT and CFT were used. When cattle in areas of low prevalence or in areas free from brucellosis are tested with the SDTH test an increase > or =2 mm in skinfold thickness should be considered indicative of infection. When the control and eradication of brucellosis is based on test-and-slaughter, an increase of > or =1 mm in skinfold thickness should be considered indicative of infection. Repeated serological testing complemented with the SDTH test in this programme will shorten the quarantine (movement control) period of a suspect herd, limiting the financial loss incurred during outbreaks of the disease. Consequently, since the SDTH test usually does not interfere with the serological diagnosis and can safely be used to establish the infection status of cattle in a suspect herd, it is opportune to consider adding the SDTH test to the procedure currently used to diagnose brucellosis in individual animals.     

Experience with simple ELISA test systems for Brucella serology in cattle, sheep and goats

The objective of this work was to use the ELISA technique for the serological surveillance for freedom of brucellosis of cattle, sheep and goats. By comparing 28 cattle sera taken after a brucellosis outbreak, 15 bovine sera supplied by the Federal Institute for Health Protection of Consumers and Veterinary Medicine (BgVV) and 497 serum slow agglutination test (SSAT) and complement fixation test (CFT) negative bovine sera from herds officially declared free of brucellosis, the ELISA technique not only shows higher sensitivity as compared to SSAT and CFT but also distinguishes clearly between positive and negative reactions. The serological comparison by SSAT, CFT and ELISA of 615 cattle, 624 sheep and 630 goat sera from herds acknowledged as brucellosis free showed equivalent specificities for both CFT and ELISA. The specificity of the SSAT was much lower, 81.1% in cattle and 96.2% in goat sera. The examination of 5796 cattle, 1337 calf, 5031 sheep and 1796 goat sera demonstrates the advantage of the ELISA technique as routine method. The possible application of the ELISA technique as a screening method for serological brucellosis tests in sheep, goats and possibly also in pigs is discussed.     

Brucellae through the food chain: the role of sheep, goats and springbok (Antidorcus marsupialis) as sources of human infections in Namibia

A confirmed case of human brucellosis motivated an investigation into the potential source of infection in Namibia. Since domestic animals are principal sources of Brucella infection in humans, 1692 serum samples were screened from sheep, goats and cattle from 4 presumably at-risk farms and 900 springbok (Antidorcas marsupialis) serum samples from 29 mixed farming units for Brucella antibodies by the Rose-Bengal test (RBT) and positive cases confirmed by complement fixation test (CFT). To assess the prevalence of human brucellosis, 137 abattoir employees were tested for Brucella antibodies using the standard tube agglutination test (STAT) and by enzyme linked immunosorbent assay (ELISA). Cattle and sheep from all 4 farms were negative by RBT and CFT but 2 of the 4 farms (Ba and C) had 26/42 and 12/285 seropositive goats, respectively. Post mortem examination of seropositive goats revealed no gross pathological lesions typical of brucellosis except enlarged mesenteric and iliac lymph nodes seen in a single buck. Culture for brucellae from organs of seropositive animals was negative. None of the wildlife sera tested positive by either RBT or CFT. Interviews revealed that besides the case that prompted the investigation, a family and another person from other farms with confirmed brucellosis shared a common history of consumption of unpasteurised goat milk, home-made goat cheese and coffee with raw milk and prior contact with goats, suggesting goats as the likely source of infection. All 137 abattoir employees tested negative by STAT, but 3 were positive by ELISA. The 3 abattoir workers were clinically normal and lacked historical connections with clinical cases. Although goats are often associated with B. melitensis, these studies could not explicitly implicate this species owing to cross-reactivity with B. abortus, which can also infect goats. Nevertheless, these data reinforce the need for a better National Control Programme for brucellosis in Namibia.     

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.     

The use of skin delayed‐type hypersensitivity as an adjunct test to diagnose brucellosis in cattle: A review

Summary

Brucellosis, caused by bacteria of the genus Brucella, is a contagious disease that causes economic loss to owners of domestic animals due to loss of progeny and milk yield. Because cattle, sheep, goats, and to a lesser extent pigs are considered to be the source of human brucellosis, serological tests have been used to screen domestic animals for antibodies against Brucella. Although the serological tests helped to eradicate brucellosis in many countries, serological tests are not always adequate to detect latent carriers of Brucella. Therefore, the use of the skin delayed‐type hypersensitivity (SDTH) test, which is independent of circulating antibodies, might improve the diagnosis of brucellosis. In the literature, however, there are conflicting reports as to the value of the SDTH test for the diagnosis of brucellosis. Some studies consider the test unreliable, whereas others advocate its use because it detects brucellosis earlier than serological tests. The objectives of this study were therefore to assess the characteristics of the SDTH test, to select a Brucella strain that will yield a suitable brucellin for use in the field, and to determine whether the use of serological tests in combination with the SDTH test improves the detection of brucellosis. The results of this study clearly show that the SDTH test detects latent carriers of Brucella and confirms brucellosis in cattle with ambiguous serological test results. Brucellins prepared from smooth or mucoid strains of Brucella are better suited for use in the field than brucellins prepared from rough strains because they detect brucellosis in cattle with acute as well as chronic infection. The SDTH test is highly specific (99.3% specificity), and repeated testing of naive cattle or cattle infected with microorganisms that serologically cross‐react with Brucella does not sensitize cattle to subsequent SDTH tests. However, it is possible that some naive cattle may serologically react to the injection of brucellin. The effect of these serological reactions on the sero‐diagnosis of brucellosis is limited, because cattle may only now and then react serologically either with the serum agglutination test (SAT) or the complement fixation test (CFT). Nevertheless, cattle infected with microorganisms that serologically cross‐react with Brucella may test seropositive for brucellosis 4 to 7 weeks after injection of brucellin, depending on the cross‐reacting microorganism. The value of the SDTH test for the diagnosis of brucellosis was demonstrated after an outbreak of brucellosis. When the SDTH test was used in combination with SAT and CFT at diagnostic threshold ≥2 mm or ≥1 mm (increase in skinfold thickness), respectively, 39/44 (88%) or 42/44 (95%) of the infected cattle were detected compared with only 27/44 (61%) when SAT and CFT were used. When cattle in areas of low prevalence or in areas free from brucellosis are tested with the SDTH test an increase ≥2 mm in skinfold thickness should be considered indicative of infection. When the control and eradication of brucellosis is based on test‐and‐slaughter, an increase of ≥1 mm in skinfold thickness should be considered indicative of infection. Repeated serological testing complemented with the SDTH test in this programme will shorten the quarantine (movement control) period of a suspect herd, limiting the financial loss incurred during outbreaks of the disease. Consequently, since the SDTH test usually does not interfere with the serological diagnosis and can safely be used to establish the infection status of cattle in a suspect herd, it is opportune to consider adding the SDTH test to the procedure currently used to diagnose brucellosis in individual animals.     

The first detection of brucella canis in cattle in the Republic of Korea

Twenty mammary lymph node samples were collected from cattle on a farm in the Republic of Korea. These cattle were serologically negative for Brucella by tube agglutination test (≤ 1:50) and serum agglutination test (≤ 1:50). Out of 20 lymph node samples, two samples were positive for Brucella growth on Brucella agar as well as blood agar. Tests for urease, hydrogen sulphide and reactions against monospecific sera A and M indicated that these two isolates (No. 15 and 16) belong to the genus Brucella. Genus specific, AMOS (abortus, melitensis, ovis, suis) and Bruce-ladder multiplex polymerase chain reaction (PCR) assays confirmed the Brucella isolates as either a B. abortus or a B. canis strain. This is the first report of the occurrence of a B. canis infection in cattle in Korea. More survey data are needed to determine whether B. canis is a significant aetiology in the cases of cattle brucellosis in Korea.     

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.     

Serologic evaluation of cattle inoculated with Toxoplasma gondii: comparison of Sabin-Feldman dye test and other agglutination tests

Six cows and 6 calves were each inoculated with 100 or 100,000 Toxoplasma gondii oocysts. Serum samples were analyzed, using the Sabin-Feldman dye test (DT), indirect hemagglutination test, latex agglutination test, and the modified direct agglutination test (MAT). Antibody titers in cows were lower than in calves. In the cows, DT titers increased briefly during the first month after inoculation, after which the titers were negative; however, T gondii was isolated from the tissues of 4 cows. Indirect hemagglutination and latex agglutination titers were generally less than 1:256. The MAT titers increased to 1:1,024 during the first month after inoculation. In 5 of the 6 cows, the MAT titers persisted. The 6th cow had a preinoculation MAT titer of 1:2,000 for 3 to 6 months. Therefore, the DT was not useful in serologic surveys for T gondii in cattle; the MAT was the most sensitive test and may be useful in the diagnosis of T gondii infection in cattle.     

The ELISA for the examination of hare sera for anti-Brucella antibodies

Hare brucellosis is caused primarily by Brucella suis biovar 2. Hares along with wild boars are the natural reservoir of this microorganism. In view of restriction of applicability of traditional serological methods the work aimed to develop the ELISA to examine hare sera for the presence of anti-Brucella antibodies. Lipopolysaccharide (LPS) antigen obtained from the strain S19 of Brucella abortus and the conjugate of antibodies against rabbit immunoglobulin with horseradish peroxidase were used in the test. Hares' sera positive and negative in the CFT were used as controls of the ELISA. The sera collected from 9 hares suspected to be infected with Brucella organisms, positive in CFT (in this number 7 hares revealed clinical symptoms or anathomopathological lesions characteristic of brucellosis), 6 sera from hares showing no symptoms of the disease, negative in CFT and 520 sera from hares monitored for brucellosis were tested. All serum samples from hares suspected for Brucella infection were positive in ELISA and 2 of them were negative in RBPT. Additionally among the samples from hares monitored 12 sera were positive in ELISA and CFT, whereas 9 sera from 12 ones were also positive in the RBPT. The obtained results indicated that the ELISA developed in our laboratory proved to be equivalent in specificity to CFT. In addition, ELISA proved to be more sensitive than RBPT for the diagnosis of Brucella infection in hares.     

Evaluation of a delayed-type hypersensitivity test for the diagnosis of Brucella abortus infection in cattle

The delayed-type hypersensitivity (DTH) test was used to diagnose brucellosis in two cows experimentally induced with brucellosis, and 176 dairy cows from a farm suspected of brucellosis. DTH test results were compared with results of the milk ring test, the serum agglutination test, the complement fixation test and the Coombs test. Cows positive in the DTH test and in one of the other tests were examined bacteriologically. In experimentally infected animals the DTH test was positive 10 days after infection, 1-4 weeks before serologic tests indicated brucellosis. Although the DTH test was positive during the whole experiment, on the one occasion when serologic titres were high, it was negative. Of the 176 dairy cows, 45 were positive in one or more serologic tests. In twelve cows (29%) the diagnosis was inconclusive because they were positive in only one of the serologic tests. In these cases the DTH test confirmed the infection. Three cows with high serologic response tested negative in the DTH test. B. abortus was isolated from 13 of 15 cows examined. We conclude that when serologic results are ambiguous, the DTH test is a useful additional technique for diagnosing brucellosis.     

Evaluation of ovine herpesvirus type 2 infections, as detected by competitive inhibition ELISA and polymerase chain reaction assay, in dairy cattle without clinical signs of malignant catarrhal fever

OBJECTIVE: To monitor ovine herpesvirus type 2 (OvHV-2) infection status and the association between OvHV-2 infection and development of clinical signs of malignant catarrhal fever (MCF) in cattle. DESIGN: Longitudinal study. ANIMALS: 30 mature adult cows and 18 cattle submitted for necropsy. PROCEDURE: Blood and milk samples were collected at monthly intervals from 30 adult cows for 20 consecutive months. Nasal and ocular swab specimens were also collected during months 9 through 20. Polymerase chain reaction (PCR) assay for detection of OvHV-2 was performed on blood, milk, nasal swab, and ocular swab specimens. Competitive inhibition ELISA (CI-ELISA) for detection of antibodies against MCF viruses was performed on serum samples obtained prior to study initiation and monthly during the last 12 months. Tissues obtained from herdmates without clinical signs of MCF that were submitted for necropsy were analyzed for OvHV-2 DNA via PCR assay for possible sites of latency. RESULTS: Initially, 8 of 30 cows had positive CI-ELISA results. Seroconversion was detected in 4 cows. Ovine herpesvirus type 2 DNA was intermittently detected in blood, milk, nasal secretions, or ocular secretions from 17 of 30 cows. Twenty-one cows had positive CI-ELISA or PCR assay results. No cattle in the study developed clinical signs of MCF. Results of PCR assays performed on tissue samples from 2 of 18 animals submitted for necropsy were positive for OvHV-2. CONCLUSIONS AND CLINICAL RELEVANCE; OvHV-2 infection can occur in cattle without concurrent development of clinical MCF. Ovine herpesvirus type 2 DNA was detected intermittently, suggesting fluctuating viral DNA loads or reinfection in subclinical cattle. A definitive site of latency was not identified from tissues obtained during necropsy.     

Brucellosis due to Brucella suis in a swine herd associated with a human clinical case in the State of S?o Paulo, Brazil

Brucella suis has been recognized as the major etiological agent of human brucellosis in areas free from Brucella melitensis infection. However, with changes in swine management, the occurrence of swine brucellosis has decreased as has the human incidence of B. suis infection. A swine brucellosis outbreak within a herd from Jaboticabal (S?o Paulo, Brazil) was detected in July 2006. The herd comprised approximately 300 sows and 1,500 finishing animals. Many sows within this herd experienced abortions, while others exhibited vaginal discharge; three sows suffered posterior paralysis. Among 271 sows, 254 (93.7%) tested positive for brucellosis by complement fixation, and among 62 randomly bled finishing animals, 17 (27.4%) also tested positive. The B. suis biovar 1 was cultured from 14 aborted fetuses and six sows. Brucella was identified using routine methods. Fourteen farm workers were tested using agglutination tests, with three workers showing evidence of Brucella antibody titers. A 39-year-old woman, who worked with maternal pigs and had direct contact with aborted fetuses, presented an agglutinating titer of 480?IU/mL and displayed clinical signs of infection. Our findings suggest that despite a reduction of swine brucellosis throughout Brazil, B. suis infection still occurs, thereby posing a zoonotic risk.