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A comparison was made with the microslide gel diffusion technique, the complement fixation test, cultural isolation, and clinical examination in detecting ram epididymitis caused by Brucella ovis. The results of the gel diffusion method are shown to be similar to those obtained by the complement fixation test and isolation of B. ovis from cultures of semen. The technique offers a reliable diagnostic method adaptable to field use in controlling ovine brucellosis and is more practical.

The counterimmunoelectrophoresis (CIE) technique was developed as a diagnostic procedure for ram epididymitis caused by Brucella ovis. CIE test results with sera from naturally and experimentally infected male sheep compared favorably with those obtained by gel diffusion and complement fixation employing the same B. ovis surface R antigen. The main advantage of CIE over gel diffusion consists in a significant reduction of the time required to detect precipitin formation, whereas both methods obviate several of the difficulties encountered with complement fixation tests for B. ovis.

Sonically treated and saline-extracted antigens of Brucella ovis, B. canis, B. abortus, and B. melitensis were compared in gel diffusion, complement fixation, and serum absorption tests. All the sonically extracted antigens showed cross-reactions with sera from animals infected or immunized with these species, whereas the saline-extracted antigens were specific for the surface of the rough or smooth colonial phase of the species or strain. The saline-extracted antigens of B. ovis and B. melitensis were both eluted as a single peak in the void volume by Sephadex G-200 column chromatography, in gel diffusion had staining characteristics of lipoproteins, but in immunoelectrophoresis showed distinct mobility patterns. Serological activity for both gel diffusion and complement fixation tests was demonstrated in the immunoglobulin G-containing fraction of sera taken from sheep 12 to 412 days after infection with B. ovis. The gel diffusion test with saline extract of B. ovis is as sensitive as the complement fixation test for the diagnosis of ram epididymitis and is more practical.

A simple gel-diffusion technique is described for the diagnosis of ram epididymitis caused by Brucella ovis. The results are shown to be very similar to those obtained by the complement-fixation test, which is currently the standard method of diagnosis. The method is suitable for use in the field and is expected to facilitate the control of ram epididymitis in areas where laboratory facilities are not available.