EVALUATION OF PROCEDURES FOR THE DIAGNOSIS OF BRUCELLA OVIS INFECTION IN RAMS

Procedures for the diagnosis of Br. ovis infection in rams were evaluated by examining 10 rams artificially infected by preputial inoculation. Observations were undertaken at weekly intervals for 1 year to follow changes in clinical, bacteriological and serological findings. Clinical lesions were detected in 1 ram 3 weeks after inoculation and in all rams by 8 weeks; lesions were undetectable in 3 rams at the completion of the trial. The presence of inflammatory cells in semen samples was the earliest indication of infection being demonstrated in 2 rams at 2 weeks and in all rams by 8 weeks; subsequently 86% of samples were positive. Br. ovis was detected in semen smears from 3 rams at 4 weeks but only once in all rams (at 27 weeks); overall 52% of semen smears were positive from 4 weeks onwards. Br. ovis was cultured from semen of 5 rams after 4 weeks and from all rams at 5 weeks; thereafter 97% of samples were positive. All rams developed significant titres to the CFT between 2 and 9 weeks; thereafter the CFT was a reliable indication of infection in 6 rams, highly suggestive in 3 and unreliable in one. By 8–10 weeks all rams developed significant titres to the IHA which were then maintained in all rams for the remainder of the trial.     

SENSITIVITY AND SPECIFICITY OF TWO MICROTITRE COMPLEMENT FIXATION TESTS FOR THE DIAGNOSIS OF BRUCELLA OVIS INFECTION IN RAMS

SUMMARY: An investigation was made into microtitre complement fixation test (CFT) procedures suitable for the serological diagnosis of naturally occurring Brucella ovis infection in rams. A procedure similar to the Australian standard procedure for bovine brucellosis was unsatisfactory when applied to sheep. Modification of the procedure by use of an initial serum and anticomplementary control dilution of 1:8 and increasing complement fixation time to 60 minutes at 37°C, greatly improved the efficiency of the test. A sensitivity of 100% was recorded for 59 serums from known infected rams and a specificity of 99.9% for 1593 serums from rams known or believed to be free of infection. Some aspects of applying CF tests to sheep serums are discussed.     

BRUCELLA SUIS INFECTION IN PREGNANT CATTLE

Six pregnant, Bos taurus cows with stages of gestation ranging from 11 to 33 weeks were each inoculated into the right conjunctival sac with 0.2 ml of a smooth culture of Brucella suis type I containing 27 x 10(6) viable organisms. The 6 cows produced 7 calves of which one single calf and one twin calf were stillborn, the cause of which was not determined. Br. suis was not isolated from any of the cows or calves using either special media or guinea pig inoculation. No abnormality was found in any of the cows or calves at autopsy. Microscopic examination of placentas and tissues from stillborn calves revealed no abnormality. Serologically, 2 weeks after inoculation all 6 cows had positive reactions to the Rose Bengal Test (RBT) and serum agglutination (SAT) titres of 25 iu to 116 iu. However, these reactions disappeared within 11 weeks. Only 2 cows had a complement fixation (CFT) titre which lasted a maximum of 5 weeks and reached a titre of 4/4. Following the anamnestic use of Br. abortus strain 45/20 vaccine on 3 of the cows, positive RBT reactions, SAT titres of 33 iu, 29 iu and 58 iu and CFT titres of 4/16, 1/8 and 3/8 respectively were recorded 6 weeks after vaccination.