Field evaluation of the protective efficacy of Mycobacterium bovis BCG vaccine against bovine tuberculosis |
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Authors: | G. Lopez-Valencia T. Renteria-Evangelista A. Licea-Navarro G. Medina-Basulto |
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Affiliation: | a Laboratorio de Tuberculosis y Brucelosis, Instituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Av. Pablo Rivera No. 1474, Colonia Independencia, Mexicali, 21290 Baja California, Mexico b Departamento de epidemiología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mexico c Centro de Investigación Científica y de Educación Superior-Ensenada, Mexico d Laboratorio de Patología, Instituto de Investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Mexico e Laboratorio de Biología Molecular Instituto de investigaciones en Ciencias Veterinarias, Universidad Autónoma de Baja California, Mexico |
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Abstract: | The protective efficacy of Mycobacterium bovis BCG (1 × 106 single dose) was evaluated under field conditions. A total of 140 male Holstein Friesian calves, one to two week-old were selected. Two groups of 70 each were formed, one group was vaccinated and the other was injected with a placebo during their second week of age and followed until 12 months of age. The study considered a positive case of tuberculosis to be an animal that had a positive reaction to the three following tests in a row: tuberculin, IFNγ PPD-B and IFNγ ESAT6-CFP10 during the 12 months of exposure. The results showed a 59.4% efficacy (IC95%: 47.64-71.16). The non-vaccinated calves were 2.4 times more at risk of becoming infected (IC95%: 1.07-5.68) compared to vaccinated animals. As a complementary test a PCR test was performed using nasal exudates in some animals from both groups using a Mycobacterium complex detection kit. All the positive PCR reactions (5/44) were found in the non-vaccinated animals. These findings suggest that the use of the BCG vaccine, even though it is not capable of protecting 100%, does prevent TB vaccinated animals from excreting bacilli in their nasal secretions at their first year of age. |
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Keywords: | Vaccination Bovine tuberculosis Mycobacterium bovis BCG Calves Protective efficacy |
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