A simplified double immunodiffusion technique for detection of Corynebacterium ovis antitoxin

A method is described for obtaining yields of Corynebacterium ovis exotoxin sufficiently high to allow use of unconcentrated supernatant and serum as the reactants in a double immunodiffusion test. C ovis supernatant with a haemolytic titre or rabbit dermal necrosis titre of 1:16,394 or greater produced readily detectable precipitation lines with specific antitoxin in the range of concentrations commonly found in sera from cases of natural C ovis infection. When used as a diagnostic screening test, sera from 32 confirmed cases of caseous lymphadenitis in sheep and goats were positive whereas sera from 16 sheep free of caseous lymphadenitis were negative. Sera from 10 out of 16 kids which had been suckled by mothers from an affected flock of goats were positive.