title: Use of the complement fixation and brucellin skin tests to identify cattle vaccinated with Brucella abortus strain RB51.
abstract: In the European Union, RB51 vaccine can be used only under strictly controlled conditions for the immunisation of cattle at risk of infection with Brucella abortus. A test is therefore necessary to distinguish vaccinated from unvaccinated animals. The complement fixation test with RB51 antigen (RB51-CFT), dot-blot and gamma-interferon used to identify vaccinated animals have been described, but sensitivity of the tests has been poor and positivity transient after calfhood vaccination. To avail of a rapid and accurate diagnostic tool, the authors produced, controlled and evaluated an experimental brucellin prepared from strain RB51 (RB51 brucellin). The potency of this brucellin was evaluated in guinea-pigs sensitised with RB51 and compared with a commercially available brucellin. Both allergens produced similar biological activity in guinea-pigs. The RB51 brucellin skin test was performed in 10 cattle 414 days after calfhood vaccination with RB51 when they were negative to the RB51-CFT. The skin test revealed 60% sensitivity (with a confidence interval of 95%, CI 30.8%-83.3%) and 100% specificity (CI 60.7%-100%). These findings limit the use of the skin test only for screening to detect RB51 vaccinated herds, not individual animals. Nevertheless, following intradermal inoculation of RB51 brucellin, a transient antibody increase to the RB51-CFT was observed, from day 9 to day 20 post inoculation with RB51 brucellin. This transient antibody increase, when evaluated in parallel with the RB51 brucellin skin test results, enables detection of individual vaccinated animals (sensitivity 100%; CI 76.2%-100%).
authors.affiliation: Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise 'G. Caporale' (IZS A&M), Campo Boario, 64100 Teramo, Italy.
authors.forename: F
authors.initials: F
authors.lastname: De Massis
authors.forename: A
authors.initials: A
authors.lastname: Giovannini
authors.forename: B
authors.initials: B
authors.lastname: Di Emidio
authors.forename: G F
authors.initials: GF
authors.lastname: Ronchi
authors.forename: M
authors.initials: M
authors.lastname: Tittarelli
authors.forename: E
authors.initials: E
authors.lastname: Di Giannatale
authors.forename: M
authors.initials: M
authors.lastname: Di Ventura
authors.forename: D
authors.initials: D
authors.lastname: Nannini
authors.forename: V
authors.initials: V
authors.lastname: Caporale