The Complement Fixation Test for Brucella Ovis

Abstract

Sir:- A project to investigate the efficacy of the complement fixation test (CFT) for the diagnosis of Brucella ovis infection in rams has recently been completed. The investigation was undertaken by field and laboratory staff of the Division of Animal Health and several practitioners. The results of CFT's done with 3 antigens by waim and cold fixation methods (WCFT and CCFT) were correlated with results of cultures done of semen from the same rams. It is our aim to publish a full report in this Journal at a later date. In view of the widespread interest in the subject some of the important findings are summarised below:

	• Semen and blood samples were collected from 541 rams in 40 flocks.
	• The type of antigen which has been used for a number of years in New Zealand was unsatisfactory. The CCFT using this antigen had a sensitivity of only 85% in 124 rams which gave positive semen cultures. These rams came from 16 infected flocks.
	• The CCFT using the best of the 3 antigens proved to be a remarkably reliable test. In the same group of infected animals mentioned above, 120 of the 124 infected rams had positive or suspicious CFT's. The sensitivity of the test was therefore 97%. The specificity was > 99% in 144 rams in 16 uninfected flocks. Only 1 suspicious titre was found in the uninfected group.
	• In 4 flocks in which B. ovis was never isolated, 18 of 58 sera gave positive or suspicious reactions. Recognition of this type of 'problem flock' is therefore important. A history and clinical picture which does not agree with serological results should always be thoroughly investigated. Semen should be collected from an appropriate number of cases for bacteriological examination. It is suspected that at least some ‘problem flocks’ may contain unreported vaccinated animals. Further investigation of ‘problem flocks’ will be an aim of the Animal Health Division in the future.