Immunological characteristics in cattle of allergens derived from smooth Brucella abortus S99

Allergens prepared from a smooth strain of Brucella abortus (S99) were used in an intradermal test for the diagnosis of brucellosis in cattle. The development and testing of the allergen from the initial less purified stages is described. The removal of serological activity noted in some of the earlier preparations can be related to the elimination of molecules of high molecular weight. The final allergen is of a high order of sensitivity and specificity and does not cause production of complement fixing or agglutinating antibodies. Intradermal testing with such an allergen could be a most useful addition to present serological procedures as it could be carried out at the same time as tuberculin testing. As a routine surveillance test, particularly in low prevalence areas, it would eliminate the necessity for extensive blood sampling and in many cases detect the infected herd before serological tests would have become positive.