Evaluation of the ring test in an epidemiological surveillance of bovine brucellosis in herds and dairies

Abstract

The ring test (RT) was analyzed regarding its application for the individual and herd bovine brucellosis diagnoses. Individual samples of milk from 464 cows and 54 composite samples of milk bucket from these animals were evaluated. The results were analyzed considering the serological results obtained by the rose bengal (RBT), tube agglutination ( TAT) and 2-mercaptoethanol (2-ME) tests. From the 464 individual milk samples analyzed by the RT, 123 (26.5%) presented positive results. From those, 30 were positive only to the RBT, 28 by the RBT/TAT/2-ME and 18 by the TAT. From the 123 positive samples by the RT, 95 came from the 2-ME seronegative animals, characterizing 77.2% of false-positive reactions and 4/341 negative reactions came from the seropositive animals, characterizing 1.2% of false-negative reactions in the individual RT. From the 54 samples of compositive milk analyzed by the RT, 17 were positive. From these positive samples, one was considered false positive since all the animals that composed it were negative by the 2-ME. Three of the composite milk samples that were negative to RT(3/37) were constituted by milk from positive animals, characterizing 8.1% of false-negative results by the RT. The individual RT showed high percentage of false-positive results, while the RT in samples from bucket detected 84.2% of the contaminated milk and 75% of the infected herds.