Abstract
Brucellosis is an endemic disease in many regions of the world. Buffalo herds have been increasing, and it is praised for the elaboration of premium products. Buffaloes are frequently infected by brucellosis and several serological tests have been employed for the detection of this disease. Here we show comparative performance among these serological tests for diagnosis brucellosis in buffaloes. Blood samples were taken from a herd of 50 adult unvaccinated animals, where abortions were reported. Sera were frozen at -20° C until processing. Buffer Plate Antigen (BPAT), Flourescent polarization (FPA) and complement fixation (CFT) were simultaneously performed according to the Manual of Standards for Diagnostics Test and Vaccines (WOAH). FPA was carried out in a SENTRY 100® (Diachemix) fluorescence polarization instrument using a 1/100 serum dilution. CFT was done through micro method, titrating the complement to 50% of hemolysis. The samecut-offs (FPA: 105 mP; CFT: 41 ICFTU (International complement fixation test units) were used as in cattle for the determination of positive and negative animals. 22 samples were positive to BPAT, FPA and CFT. All sera that were positive for BPAT showed strong agglutination. FPA results obtained in the positive sera were in the range between 170 and 250 mP while the average measurement of the negative control was 75 mP. CFT was positive at very high serum dilutions in all confirmed samples. No false positive results for BPAT were obtained in any sample. FPA and CFT confirmed exactly the same results that BPAT anticipated. Serological diagnosis for brucellosis in buffaloes is sometimes controversially. These results suggested that FPA might be used as a confirmatory test for brucellosis in buffalo, due to the same performance relative to CFT, its adjustable cut- off useful in different epidemiological situations, its reliability and ease of performance.CFT is a very useful test, as long as proper equipment and trained laboratory professionals are available. We show here a very precise methodology using BPAT as screening test and FPA as confirmatory one. A larger study is needed in order to obtain a cut-off that responds to the current epidemiological situation of brucellosis in buffaloes.
