Determination of sensitivity and specificity of the Nocardia asteroides skin test for detection of bovine mammary infections caused by Nocardia asteroides and Nocardia caviae.

A total of 116 cows from 4 dairy herds in California were used to determine the sensitivity and specificity of extracellular antigen of Nocardia astero des for possible detection of bovine mastitis caused by N asteroides and N caviae. Three different positive criteria were used. These criteria gave different sensitivity and specificity to the skin test. The highest sensitivity of 80% and highest specificity of 96.04% were obtained by combining 2 criteria. The study found no cross-reaction between N asteroides antigen and Mycobacterium fortuitum or N asteroides and tuberculin skin tests. There was cross-reaction between N asteroides antigen and N caviae infection.