Advanced studies on serological diagnosis of bovine brucellosis

This investigation is concerned with the diagnosis and differentiation between Brucella infected and vaccinated cattle.The animals included in this study were180 naturally infected non vaccinated cows in governmental farm (group 1), 125 brucella free cows in which strain 19 vaccination had never been practiced (group 2) and 530 strain 19 vaccinated cows (group3). Sera from these animals were examined for brucellosis using Rose Bengal plate test ( RBPT),Buffer acidified plate antigen test (BAPAT),Rivanol test( Riv.T), Tube agglutination test(TAT),Complement fixation test( CFT) .For cows suspected to be infected with brucellosis, the results revealed that the percentage of positive reactors for RBPT, BAPAT, Riv.T, TAT and CFT were 139(77.2%), 143(79.4%), 130(72.2%), 146(81.1%) and 131(72.8%) respectively. While for brucella free cows, the percentage of positive reactors were 2(1.6%), 4(3.2%), 1(0.8%), 5(4%) and 1(0.8%) respectively. In this study the humeral immune response in serum of cows vaccinated with s19 vaccine using RBPT, BAPAT, Riv.T, TAT, and CFT revealed that agglutinins were quite evidenced 2 weeks post vaccination. The number of animals positive for Brucella antibodies reached maximum at 4 weeks post vaccination. The incidence of isolation from supramamary and retropharyngeal L.n, liver , spleen and milk samples were 54%, 48%, 50% , 38%4and 30.3% respectively. the obtained results indicate that brucella melitensis biovar 3 still the prevalent type affecting cattle in Egypt.The Immunobolt was performed with pooled sera from brucella infected and S19 vaccinated cows, the sera of brucella infected cows develop strong antibody reaction with all bands in LPS antigen . S19 vaccinated cows sera from 4 to 12 weeks post vaccination developed antibody reactivity against LPS similar to brucella infected cow. Regarding to CPE antigen the brucella infected cow sera developed antibody reaction against 80.88, 58.07, 38.33, 36.14, 27.08, 25.71, 18.01 and 10.28 KDa bands, 4 weeks post vaccination developed antibody reaction against 80.88, 58.07 and 38.33 KDa bands while no reaction was noticed against 18.01 KDa band . While sera of S19 vaccinated cows 6,8 and 10 weeks post vaccination developed antibody reaction against 80.88 and 50.07 KDa bands and very faint reaction against 80.88 ,50.07 KDa band only, for sera collected at 12 weeks post vaccination developed very faint antibody reaction against 80.88 and 50.07KDa bands. The antibody reaction disappears in sera collected 16,24 weeks post vaccination. . Sera from these animals were examined for brucellosis using Indirect Enzyme linked immunosorbent assay (iELISA) using Iipopolysaccharides( LPS) or Cytoplasmic Protein Extract ( CPE) as coating antigens. The highest values of the ability of serological tests to differentiate S19 vaccinated animals from those infected ones were detected in iELISA using CPE as coating antigen and lowest values were seen in iELISA using LPS as coating antigen. In the present study the results revealed that PCR assay also able to differentiate S19 vaccinated animals from those infected ones