Clinical and histological features of brucellin skin test responses in Brucella suis biovar 2 infected pigs

Current serological tests for swine brucellosis detect antibodies to the Brucella O-polysaccharide (O/PS). However, when infections by bacteria carrying cross-reacting O/PS occur, these tests suffer from false positive serological reactions (FPSR), and the skin test with Brucella soluble protein extracts is the best diagnostic alternative to differentiate true Brucella suis infections from FPSR in pigs. Since this test has been seldom used in B. suis infected swine, the clinical and histological features involved have not been described properly. Here, we describe the clinical and histological events in B. suis biovar 2 infected pigs skin tested with a cytosoluble O/PS free protein extract from rough Brucella abortus Tn5::per mutant. A similar extract from rough Ochrobactrum intermedium was also used for comparative purposes. No relevant differences were evidenced between the homologous and heterologous allergens, and the main clinical feature was an elevated area of the skin showing different induration degrees. Moreover, an important vascular reaction with hyperemia and haemorrhage was produced in most infected sows 24-48 h after inoculation, thus facilitating the clinical interpretation of positive reactions. Histologically, combined immediate (type III) and delayed (type IV) hypersensitivity reactions were identified as the most relevant feature of the inflammatory responses produced.

Efficacy of bp26 and bp26/omp31 B. melitensis Rev.1 deletion mutants against Brucella ovis in rams

Brucella melitensis Rev.1 is the most effective vaccine against B. ovis infection in sheep but induces antibodies interfering with B. melitensis diagnosis. Brucella BP26 and Omp31 proteins are differential diagnostic antigens. Single or double bp26 and omp31 Rev.1 deletion mutants have been proven effective against B. melitensis in sheep. Here, the CGV26 (deleted in bp26 gene) and CGV2631 (deleted in both bp26 and omp31 genes) mutants have been tested for efficacy against B. ovis in rams. Either inoculated subcutaneously or conjunctivally, both mutants conferred significant protection against B. ovis. The protection induced by CGV26 was similar to that of Rev.1 but significantly higher than that conferred by CGV2631. In conclusion, the CGV26 mutant, in association with the adequate diagnostic strategy, could be a useful alternative to Rev.1 for sheep vaccination against B. ovis infections in those countries performing simultaneously B. melitensis and B. ovis eradication campaigns.

Evaluation of the diagnostic accuracy of the modified agglutination test (MAT) and an indirect ELISA for the detection of serum antibodies against Toxoplasma gondii in sheep through Bayesian approaches

The diagnostic accuracies of the modified agglutination test (MAT) and indirect ELISA test for the detection of serum antibodies against Toxoplasma gondii in sheep were evaluated through Bayesian approaches on two populations of sheep created from three different groups of animals (T. gondii-aborted ewes, colostrums-deprived newborn lambs, and ewe-lambs and adult ewes with unknown T. gondii infection status). Tests showed a high degree of agreement (kappa statistic = 0.93; 95% confidence interval = 0.87, 0.98) and a significant specificity (Sp) correlation (gamma(Sp) = 0.26; 95% credibility interval = 0.017, 0.61). When prior information was used for all unknown parameters the posterior medians for the sensitivity (Se) and Sp of the MAT and ELISA were, respectively, 92.6% (95% credibility interval = 85.2, 96.9), 95.5% (89.9, 98.7), 90.5% (83.4, 95.6), and 97.8% (94.2, 99.5). These estimates remained similar when uninformative priors were included. The Se estimates of the MAT and ELISA were higher than those obtained on pigs in other study using the same approach (Se = 80.6% and Sp = 89.5% for the MAT, and Se = 71.5% and Sp = 85.5% for the ELISA [Georgiadis, M.P., Wesley, O.J., Gardner, I.A., Singh, R., 2003. Correlation-adjusted estimation of sensitivity and specificity of two diagnostic tests. Appl. Stat. 52, 63-78]. This finding supported the believe that test performances may vary when applied on different animal species. Thus, if these tests are planned to be used on animal species other than sheep or pigs, their diagnostic accuracy should be re-assessed to prevent biased inferences from their results.

Chronic meningoencephalitis associated with Brucella sp. infection in live-stranded striped dolphins (Stenella coeruleoalba)

A chronic, non-suppurative meningoencephalitis was found in three young striped dolphins (Stenella coeruleoalba) during routine neuropathological examination of marine mammals live-stranded on the Scottish coast. In all three dolphins the lesions were associated with the isolation of a Brucella sp. from the brain and with the immunohistochemical detection of brucella antigen. Moreover, antibodies to Brucella spp. were detected in the two dolphins that were subjected to serological examination. Immunohistochemical and serological examinations for morbillivirus antigen and antibodies, respectively, were negative in all cases. Although brucella infection of marine mammals has been extensively documented in recent years, its association with lesions and disease is less well recognized. The present report provides the first description of an association between Brucella sp. infection and neuropathological changes in a cetacean species.

A Brucella ovis antigenic complex bearing poly-epsilon-caprolactone microparticles confer protection against experimental brucellosis in mice

A hot saline antigenic extract (HS) from Brucella ovis was encapsulated in poly-epsilon-caprolactone microparticles (PEC), and tested as a vaccine against B. ovis and B. abortus infections in mice. Subcutaneous but not oral administration in BALB/c mice of the HS-PEC induced high amounts of IFN-gamma and IL-2 but low quantities of IL-4 suggesting a combined Th1/Th2 cellular immune response. The vaccine administered either subcutaneously or orally protected mice against B. ovis infection. Such protection was similar to that provided by the reference living attenuated B. melitensis Rev. 1 vaccine. By contrast, only the subcutaneous vaccination with HS-PEC was as effective as Rev. 1 in conferring protection against B. abortus infection. The use of free HS or empty PEC microparticles did not produce any protective effect.

Experimental Brucella ovis infection in pregnant ewes

Forty yearling Brucella-free ewes were inoculated with Brucella ovis by the conjunctival route in mid or late first pregnancy. Only a few ewes excreted B ovis during pregnancy and gave birth to stillborn lambs, but most of them excreted the organism at lambing or during lactation. One of the 11 lambs which were born alive but died before they were weaned was found to be infected postmortem. In contrast, none of the 46 surviving lambs which were reared in isolation until adulthood, was found to be infected. At weaning, the 40 ewes were mated again with five Brucella-free rams. Although many of the ewes excreted B ovis, none of the rams was found to be infected when necropsied after mating. Most of the ewes that became pregnant, all having excreted B ovis during their first pregnancy, cleared the infection during the second pregnancy. However, three remained persistently infected and excreted B ovis in their milk throughout the second lactation. None of the lambs born to these three ewes was found to be infected when necropsied at weaning.

Transmission of Brucella melitensis from sheep to lambs

Forty-one pregnant sheep showing positive immune responses to Brucella melitensis in serological or allergic tests were selected from naturally infected flocks and kept in an isolated pen for lambing. The resulting 62 lambs were maintained in the same pen with their dams during lactation. When the lambs were weaned, the dams were slaughtered for bacteriological study and the lambs were reared in a clean pen. Fourteen ewes excreted B melitensis during lactation and 17 were found to be infected postmortem, B melitensis was not isolated from seven lambs (three born to infected dams) which died after birth or from eight seronegative lambs (four born to infected dams) which were slaughtered between two and seven months after weaning. However, one permanently seropositive lamb born to a culture-negative dam was found to be infected when necropsied five months after weaning. The remaining 46 lambs were reared until adulthood and slaughtered at intervals for bacteriological study. Four ewe lambs (two born to culture-negative dams) were found to be infected postmortem, but were negative in immunological tests for B melitensis.

Antibody and delayed-type hypersensitivity responses to Ochrobactrum anthropi cytosolic and outer membrane antigens in infections by smooth and rough Brucella spp

Immunological cross-reactions between Brucella spp. and Ochrobactrum anthropi were investigated in animals and humans naturally infected by Brucella spp. and in experimentally infected rams (Brucella ovis infected), rabbits (Brucella melitensis infected), and mice (B. melitensis and Brucella abortus infected). In the animals tested, O. anthropi cytosolic proteins evoked a delayed-type hypersensitivity reaction of a frequency and intensity similar to that observed with B. melitensis brucellin. O. anthropi cytosolic proteins also reacted in gel precipitation tests with antibodies in sera from Brucella natural hosts with a frequency similar to that observed with B. melitensis proteins, and absorption experiments and immunoblotting showed antibodies to both Brucella-specific proteins and proteins common to Brucella and O. anthropi. No antibodies to O. anthropi cytosolic proteins were detected in the sera of Brucella-free hosts. Immunoblotting with sera of Brucella-infected sheep and goats showed immunoglobulin G (IgG) to Brucella group 3 outer membrane proteins and to O. anthropi proteins of similar molecular weight. No IgG to the O-specific polysaccharide of O. anthropi lipopolysaccharide was detected in the sera of Brucella-infected hosts. The sera of sheep, goats, and rabbits infected with B. melitensis contained IgG to O. anthropi rough lipopolysaccharide and lipid A, and B. ovis and O. anthropi rough lipopolysaccharides showed equal reactivities with IgG in the sera of B. ovis-infected rams. The findings show that the immunoresponse of Brucella-infected hosts to protein antigens is not necessarily specific for brucellae and suggest that the presence of O. anthropi or some related bacteria explains the previously described reactivities to Brucella rough lipopolysaccharide and outer membrane proteins in healthy animals.

Comparison of two selective media for the isolation of Brucella melitensis from naturally infected sheep and goats

The efficacy of two selective media for the isolation of Brucella melitensis from naturally infected sheep and goats was compared. Two hundred and eighty sheep and 60 goats belonging to B melitensis-infected flocks were slaughtered and samples of milk (when available) and seven tissues were taken from each animal for bacteriological analyses. A modified Thayer-Martin's medium was more sensitive than Farrell's medium; by the combined use of both media 142 infected sheep and 40 infected goats were detected, and 486 of the samples from the sheep and 179 of the samples from the goats were found to be infected.

The Brucella abortus RB51 vaccine does not confer protection against Brucella ovis in rams

The protective efficacy against Brucella ovis of the live vaccine Brucella abortus strain RB51 has been evaluated in rams using the attenuated B. melitensis strain Rev 1 as a reference vaccine. Sixteen Brucella-free rams, 6 months of age, were vaccinated subcutaneously with 4.18 x 10(10) c.f.u. RB51. Sixteen rams of the same condition and age were vaccinated subcutaneously the same day with 1.1 x 10(9) c.f.u. Rev 1. Fifteen similar rams were kept unvaccinated as controls. Six months after vaccination all rams were challenged with 3 x 10(9) c.f.u. B. ovis and slaughtered 8 weeks thereafter for bacteriological and pathological studies. The percentage of rams that were found infected was 68% (Rev 1), 100% (RB51) and 100% (controls). At necropsy, the percentage of organs found to be infected was significantly lower (p < 0.0005) in Rev 1-vaccinated (34%) than in RB51-vaccinated rams (74%) or controls (69%). In conclusion, the RB51 vaccine did not confer protective immunity against B. ovis in rams.

Brucella ovis infection in two flocks of sheep

Brucella ovis infection could not be eradicated from two flocks of sheep despite serologically testing and culling the infected rams for four years. The hypothesis that the ewes played a major role in the maintenance of the infection in both flocks was investigated by using serological, bacteriological and pathological criteria. Specific antibodies against B ovis were demonstrated in 71 ewes in the two flocks. Forty-four of the seropositive ewes were slaughtered for bacteriological and pathological studies and B ovis was isolated from 16 of them; the uterus was the target organ of the infection, although extrauterine infection was also demonstrated in some of the infected ewes.

Evaluation of allergic and serological tests for diagnosing Brucella melitensis infection in sheep

A total of 291 unvaccinated sheep from Brucella melitenesis-infected flocks were examined for delayed-type hypersensitivity (DTH) responses with Brucellergene commercial allergen and with cold saline extract and cytosol from rough B. melitensis 115, and their sera were tested in the rose bengal test (RBT), complement fixation test (CFT), and enzyme-linked immunosorbent assay (ELISA) with lipopolysaccharide. DTH reactions were maximal after 72 h, with no intensity differences among allergens, inoculation sites (eyelid and tail), and doses tested. There were no differences in the results recorded by visual inspection and palpation of inoculation sites, by measuring skin thickness with a caliper, or by microscopic examination of samples taken at necropsy. Six days after DTH testing, energy was observed in 100% of the animals, and 100% reactivity was recovered only after 24 days. All animals were necropsied, and thorough bacteriological searches were performed. The sensitivities found with the 140 animals from which B. melitensis was isolated were ELISA, 100%; DTH, 97.1%; RBT, 92.1%; and CFT, 88.6%. Those results put into question the value of RBT and CFT as screening and confirmatory tests for sheep brucellosis and at least indicate that their standardization should be modified. For 151 tested sheep from which B. melitensis was not isolated, the percentages of positive animals were ELISA, 100%; DTH, 94.0%; RBT, 57.6%; and CFT, 53.6%. All tests were negative for 100 tested sheep from Brucella-free flocks. The different results of bacteriological and immunological tests suggest the usefulness of developing indirect tests able to distinguish truly infected animals from those that have developed an immunological response.

Efficacy of Brucella suis strain 2 vaccine against Brucella ovis in rams

The protective efficacy against Brucella ovis of live vaccine Brucella suis strain 2 (S2) and Brucella melitensis strain Rev 1 has been evaluated in rams. Fourteen 4-month-old Brucella-free Aragonesa rams were vaccinated conjunctivally with 2 x 10(9) c.f.u. S2. Sixteen rams of the same breed, condition and age were conjunctivally vaccinated the same day with 1.6 x 10(9) Rev 1. Thirteen rams were unvaccinated controls. Eight months after vaccination all rams were challenged with 6 x 10(9) c.f.u. B. ovis and slaughtered 2 months thereafter for bacteriological and pathological studies. The percentage of infection in the group vaccinated with Rev 1 (43.7%) was significantly lower (p < 0.05) than that of the S2-vaccinated animals (78.6%) and unvaccinated controls (84.6%). No significant differences were found when comparing the percentages of infection corresponding to S2-vaccinated and control groups. The degree of infection (percentage of necropsy samples infected) was significantly lower in Rev 1-vaccinated (13%) than in S2-vaccinated (36.9%) or control groups (47.4%) (p < 0.001). However, no significant differences were found when comparing S2-vaccinated and control groups.

Evaluation of whole cell and subcellular vaccines against Brucella ovis in rams

Five antigen preparations from Brucella ovis strain REO 198 were incorporated with the pluronic polymer L-121 and muramyl dipeptide and tested as vaccines against B. ovis infection of rams. The antigenic preparations were: (1) a fraction enriched in outer membrane proteins and rough lipopolysaccharide (hot saline extract, HS); (2) the proteins from HS substantially free of lipopolysaccharide; (3) outer membrane blebs; (4) outer membrane-peptidoglycan complexes extracted with detergent; (5) killed whole cells. The experimental vaccines were compared with two standard vaccines, rough Brucella abortus 45/20 whole killed cells in an oil based adjuvant, and live Brucella melitensis Rev 1. Immunizations with non-living vaccines were performed on two occasions, 18 weeks apart. The rams were challenged with a virulent strain of B. ovis 31 weeks after the second vaccination and slaughtered 15 weeks thereafter. Rates of infection in groups vaccinated with Rev 1 (33%), and HS (40%) were significantly lower (P < 0.005 and P < 0.025, respectively) than that in the non-vaccinated control group (87%). Strain 45/20 was the only other vaccine that conferred a significant level of protection (50%) (P < 0.05). The organ distribution of the infection and the level of colonization of infected organs did not differ significantly between infected animals in the various vaccine groups and those in the unvaccinated control group. No statistically significant relationship was detected between the magnitude of the antibody responses to the HS extract, to outer membrane proteins, or to the rough lipopolysaccharide, and freedom from infection. The results indicate that the HS extract of B. ovis may represent a useful alternative to B. melitensis Rev 1 or B. abortus 45/20 as a vaccine against B. ovis.

Role of an intramammary device in protection against experimentally induced staphylococcal mastitis in ewes

An intramammary device (IMD) was adapted for use in ewes; this device was made of abraded polyethylene material (1.7 mm in diameter, 47 mm long) and formed a 15-mm-diameter loop in the gland cistern. The IMD was inserted in 1 gland in each of 43 ewes. A significant (P < 0.0001) increase in milk somatic cell count (SCC) was observed in glands provided with an IMD. This increase was attributable to an increase in neutrophil numbers and was observed during the first 12 weeks after insertion. The IMD had a protective effect against experimentally induced staphylococcal mastitis (Staphylococcus aureus and S epidermidis), although different milk SCC were required for protection from each bacterial species in most ewes (10(6) and 2 x 10(5) cells/ml, respectively). Histologic studies revealed that the IMD induced local squamous metaplasia in the glandular part of the lactiferous sinus. Erythrocytes were found in milk from glands provided with an IMD throughout the studied period (35 days of the 45-day lactation) and, in some cases, blood clots were observed during the first 2 weeks of lactation. Glands with IMD also had lower milk production and quality at 30 and 32 days of lactation. Eight ewes with IMD were studied throughout a subsequent lactation. Milk from the IMD-containing glands had an increase in SCC, as in the previous lactation period; did not contain blood clots or erythrocytes; and had normal composition (similar to that in glands without the IMD).

Evaluation of vaccines and of antigen therapy in a mouse model for Brucella ovis

A mouse model was developed to study Brucella ovis infection. The evolution of the number of B. ovis per spleen of mice inoculated intravenously, intraperitoneally or subcutaneously was found to be independent of the sex of the mice. The number of B. ovis increased in the spleen when increasing the challenge dose up to 1.7 x 10(7). At higher doses of challenge, the response remained constant. In this model it was observed that the inoculation of Brucella melitensis Rev 1 vaccine or subcellular B. ovis hot saline antigens during both the acute and chronic phases did not modify the time course of B. ovis infection. Finally, the model was found suitable to determine the efficacy of anti-B. ovis vaccines. B. melitensis Rev 1 (2.2 x 10(5) c.f.u.) and B. suis strain 2 (1.2 x 10(7) c.f.u.) live vaccines but not the inactivated B. melitensis H38 vaccine conferred protection against B. ovis.

Comparison of subcutaneous and conjunctival routes of Rev 1 vaccination for the prophylaxis of Brucella ovis infection in rams

The serological response and protection conferred against Brucella ovis by the Rev 1 vaccine was evaluated in both adult (experiment 1) and young rams (experiment 2) vaccinated either subcutaneously or conjunctivally. In experiment 1 the Rev 1 vaccine protected 55.5 per cent and 100 per cent, respectively, of subcutaneously and conjunctivally vaccinated rams against three consecutive challenges that infected 100 per cent of unvaccinated controls. In experiment 2, Rev 1 protected 100 per cent of rams vaccinated subcutaneously and 70 per cent of those vaccinated conjunctivally against a challenge dose able to infect all the unvaccinated controls. The serological response after vaccination was significantly lower in rams vaccinated conjunctivally than in those vaccinated subcutaneously.

Efficacy of long-acting oxytetracycline alone or in combination with streptomycin for treatment of Brucella ovis infection of rams

Twenty-four rams inoculated with Brucella ovis by conjunctival and preputial routes were treated with a long-acting oxytetracycline alone or in combination with dihydrostreptomycin sulfate. The combined treatment eliminated Brucella ovis from 11 of 12 (91.6%) treated rams. Only 4 of 12 (33.3%) rams treated with oxytetracycline alone were bacteriologically negative. Neither treatment resolved clinical epididymitis in 2 rams affected before treatment. Many rams had pathologic lesions in the epididymis and ampullae, which limited the efficacy of antibiotic treatment.

Immunization with Brucella melitensis Rev 1 against Brucella ovis infection of rams

The efficacy of Brucella Melitensis Rev 1 vaccine (Rev 1) for the prophylaxis of Brucella ovis ram epididymitis was evaluated. Twenty-nine 3-month-old rams were vaccinated with 2 X 10(9) Rev 1 and 14 were revaccinated with 5 X 10(8) at 14 months of age. Six rams remained unvaccinated as a control group. All rams were challenged with 5 X 10(8) B. ovis at 21 months of age. Before being slaughtered 8 weeks later, only one vaccinated ram developed epididymitis while four of the six control rams developed testicular alterations. Genital and selected extragenital organs and lymph nodes were removed at slaughter and inoculated on selective media. B. ovis was isolated from 26.6% of the vaccinated rams, 21.4% of the revaccinated rams and 100% of control rams. Portions of epididymis, testes and vesicular glands were also used for pathological studies. More severe lesions were observed in control rams than in vaccinated ones. In conclusion, these results show that vaccination of young lambs, followed or not by revaccination, is a suitable method for the prophylaxis of B. ovis infection of rams.