Comparison of diagnostic tests for detecting bovine brucellosis in animals vaccinated with S19 and RB51 strain vaccines

Research (Published online: 14-10-2023)

9. Comparison of diagnostic tests for detecting bovine brucellosis in animals vaccinated with S19 and RB51 strain vaccines

Marcelo Ibarra, Martin Campos, Benavides Hernán, Anthony Loor-Giler, Andrea Chamorro, and Luis Nuñez

Veterinary World, 16(10): 2080-2085

Marcelo Ibarra: Facultad de Industrias Agropecuarias y Ciencias Ambientales, Carrera Agropecuaria, Universidad Politécnica Estatal del Carchi, Antisana S/N y Av Universitaria, Tulcán Ecuador 040102; Facultad de Ciencias Veterinarias, Universidad Nacional de Rosario, Boulevard Ovidio Lagos y Ruta 33 Casilda-Santa Fe-Argentina.

Martin Campos: Facultad de Industrias Agropecuarias y Ciencias Ambientales, Carrera Agropecuaria, Universidad Politécnica Estatal del Carchi, Antisana S/N y Av Universitaria, Tulcán Ecuador 040102; Facultad de Ciencias Veterinarias, Universidad Nacional de Rosario, Boulevard Ovidio Lagos y Ruta 33 Casilda-Santa Fe-Argentina.

Benavides Hernán: Facultad de Industrias Agropecuarias y Ciencias Ambientales, Carrera Agropecuaria, Universidad Politécnica Estatal del Carchi, Antisana S/N y Av Universitaria, Tulcán Ecuador 040102.

Anthony Loor-Giler: Facultad de Ingeniería y Ciencias Aplicadas, Carrera de Ingeniería en Biotecnología, Universidad de Las Américas, Antigua Vía a Nayón S/N, Quito EC 170124 Ecuador.

Andrea Chamorro: Facultad de Industrias Agropecuarias y Ciencias Ambientales, Carrera de Enfermeria, Universidad Politécnica Estatal del Carchi, Antisana S/N y Av Universitaria, Tulcán Ecuador 040102.

Luis Nuñez: Facultad de Ciencias de la Salud, Carrera de Medicina Veterinaria, Universidad de Las Américas, Antigua Vía a Nayón S/N, Quito EC 170124 Ecuador; One Health Research Group, Universidad de Las Américas, Quito, Ecuador.

Background and Aim: The diagnosis of bovine brucellosis in animals vaccinated with strain-19 (S19) and Rose Bengal (RB)-51 strain vaccines can be misinterpreted due to false positives. This study aimed to compare diagnostic tests for detecting bovine brucellosis in animals vaccinated with S19 and RB51 vaccine strains.

Materials and Methods: Two groups of 12 crossbred Holstein calves between 6 and 8 months of age were used. On day 0, blood samples were collected from the animals, and the competitive enzyme-linked immunosorbent assay was used for serological diagnosis of bovine Brucellosis. All animals tested negative. After the first blood collection, the animals were subcutaneously vaccinated: one group received the S19 vaccine and the other received the RB51 vaccine. From the 3rd month after vaccination, all animals were sampled. Sampling was repeated every 2 months until the 7th month. Serological diagnosis of bovine brucellosis was performed using RB, tube serum agglutination test (SAT), SAT with 2-mercaptoethanol (SAT-2Me), and fluorescence polarization assay (FPA).

Results: Animals vaccinated with S19 showed positive results with the RB, SAT, and SAT-2Me tests in all months of post-vaccination diagnosis. In animals vaccinated with S19, FPA showed positive results at months 3 and 5 and negative results at month 7, indicating that this test discriminates vaccinated animals from infected animals 7 months after vaccination. Rose Bengal, SAT, SAT-2Me, and FPA tests showed negative results in animals vaccinated with RB51 in all months of diagnosis.

Conclusion: Animals vaccinated with S19 may test positive for brucellosis using RB, SAT, or SAT-2Me tests 7 months later. Fluorescence polarization assay is an optimal alternative for diagnosing animals in the field, thereby preventing false positives, and consequently, unnecessary confiscations of animals. Animals vaccinated with RB51 tested negative with RB, SAT, SAT-2Me, and FPA tests in all months of diagnosis, confirming that the tests are ineffective for diagnosing brucellosis caused by rough strains.