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Previously unrecognized Brucella species have been isolated from a number of marine mammals, including harbor seals (Phoca vitulina richardsi) in the Puget Sound area of the state of Washington. Because of the presence of dairy herds in proximity to the harbor seal populations, a study was conducted to determine the effects of the harbor seal Brucella isolate in experimentally inoculated cattle. Six pregnant cattle were exposed by intravenous injection (n = 3) or intraconjunctival inoculation (n = 3). Two pregnant cows were intravenously injected with saline and served as controls. All of the cows receiving the Brucella seroconverted on 1 or more tests commonly used for the detection of Brucella abortus infection. Two of the cattle receiving the intravenous inoculation aborted, and brucellae were demonstrated in the fetuses and dams immediately following abortion. The remaining 4 Brucella-inoculated animals and their fetuses were culture negative for the organism at 14 weeks postinoculation. Results of this study indicate the marine mammal Brucella is capable of producing seroconversion and abortion in cattle but is less pathogenic in that species than B. abortus.

The complement fixation (CF) test commonly is used to identify cattle infected with Anaplasma marginale prior to interstate or international movement. Estimates of the accuracy of the CF test in detecting animals persistently infected with A. marginale vary widely. In this study, the sensitivity and specificity of the CF test for detection of carrier animals was determined using serum from 232 cattle previously defined as A. marginale positive or negative by nested polymerase chain reaction methods and hybridization. Considering results from 2 independent laboratories and interpreting a 1:5 suspect reaction as positive, the best estimate of CF test sensitivity was 20%, with a specificity of 98%. Using a 1:10 cutoff, sensitivity decreased to 14% and specificity increased to 99%. Results of this study indicate that the CF test is ineffective for identifying cattle persistently infected with A. marginale and thus is inadequate for anaplasmosis regulatory and surveillance programs.

Specimens of blood, lymph nodes, spleens, and genitalia were collected at slaughter from seven 3- and 4-year-old male bison that had recently become seropositive for brucellosis. The animals were from a captive herd of approximately 3,500 bison located in central South Dakota. Brucella abortus biovar 1 was isolated from 2 or more specimens from each of 6 bison. Severe necrotizing and pyogranulomatous orchitis was present in 1 testicle from 1 bull, and 4 animals had mild to marked seminal vesiculitis. Immunohistochemical staining labeled organisms in seminal vesicles and the testicle with orchitis. Ultrastructurally, intact bacilli were present in cytoplasmic vacuoles of some macrophages; other macrophages contained intracytoplasmic aggregates of calcified coccobacilli.

This study was designed to determine if Brucella abortus strain RB51, which expresses small amounts of the lipopolysaccharide O side chain, would cause positive responses on brucellosis serologic surveillance tests when given to adult cattle that were vaccinated as calves with B. abortus strain 19. Cattle vaccinated as adults with strain RB51 that had been vaccinated as calves with strain 19 (n = 40) had significantly greater antibody titers (P < 0.05) against strain RB51 at 4 and 8 weeks postvaccination in the dot blot assay than did animals (n = 10) not vaccinated with strain RB51. When evaluated using the card or buffered acid plate agglutination presumptive tests, 7 strain RB51 vaccinates tested positive at either 4 or 8 weeks following vaccination as compared with 4 cattle in the control group that were not vaccinated with strain RB51. One strain RB51 vaccinate was scored as suspect on the standard tube agglutination (STA) test at 8 weeks following vaccination. Remaining samples from strain RB51 vaccinates tested negative on the STA, complement fixation (CF), rivanol, and particle concentration fluorescence immunoassay (PCFIA) confirmatory tests. Samples from 2 control cattle were PCFIA positive at time 0; 1 of these animals was CF positive throughout the study. This study suggests that use of strain RB51 in cattle vaccinated with strain 19 as calves will not cause positive responses on confirmatory tests and will not impair brucellosis serologic surveillance efforts.

Interlaboratory reproducibility of an absorbed enzyme-linked immunosorbent assay (ELISA) kit for detection of bovine serum antibodies to Mycobacterium paratuberculosis was evaluated. A panel of 30 bovine sera (15 positives and 15 negatives) was tested in triplicate microtiter wells on each of 2 days at 8 different laboratories. One laboratory had invalid results because of positive or negative serum control optical density (OD) readings beyond the acceptable range specified by the kit. The coefficient of variation (CV) for mean OD values was influenced by low ODs on test negative sera at 2 laboratories, thus the CVs on positive sera were considered a more representative measure of kit reproducibility. Between-well CVs averaged 6.7% +/- 2.8% (mean +/- standard deviation), and between-day CVs averaged 14.5% +/- 9.8% among the 7 laboratories with valid assays on the 15 positive sera. The OD values were converted to positive or negative classifications for each assay well, and the results were compared. Among 1,392 assays in 7 laboratories, 98.6% were in agreement. Eleven of 18 discrepant results were due to a sample that consistently gave OD values near the cutoff for a positive test. Exclusion of that serum from the analysis resulted in a 99.8% rate of agreement among laboratories. Results indicated that the absorbed ELISA kit provided reproducible results within and between laboratories.