Field evaluation of the efficacy of Mycobacterium bovis bacillus Calmette-Guérin against bovine tuberculosis in neonatal calves in Ethiopia
Clinical and Vaccine Immunology
Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia; TB Research Group, Veterinary Laboratories Agency, Weybridge, New Haw, Addlestone, Surrey KT15 3NB, United Kingdom; Armauer Hansen Research Institute, P.O. Box 1005, Addis Ababa, Ethiopia; Division of Infectious Diseases, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
In developing countries, the conventional test and slaughter strategy for the control of bovine tuberculosis is prohibitively expensive, and alternative control methods such as vaccination are urgently required. In this study, the efficacy of Mycobacterium bovis bacillus Calmette-Guérin (BCG) for protection against bovine tuberculosis (bTB) was evaluated in Holstein calves under field conditions in Ethiopia. Thirteen neonatally vaccinated and 14 control calves were exposed for 10 to 23 months to skin test reactor cows. Gamma interferon (IFN-γ) testing, comparative intradermal tuberculin testing, postmortem examination, and bacteriological culture were used for the evaluation of BCG efficacy. The overall mean pathology score was significantly (P < 0.05) higher in control calves than in vaccinated calves. Culture positivity for Mycobacterium bovis was higher in the control calves than in the vaccinated calves, and significantly more BCG-vaccinated animals would have passed a standard meat inspection (P = 0.021). Overall, the protective efficacy of BCG was between 56% and 68%, depending on the parameters selected. Moreover, by measuring gamma interferon responses to the antigens ESAT-6 and CFP-10, which are present in M. bovis but absent from BCG, throughout the experiment, we were able to distinguish between vaccinated animals that were protected against bTB and those animals that were not protected. In conclusion, the present trial demonstrated an encouraging protective effect of BCG against bTB in a natural transmission setting in Ethiopia. Copyright © 2010, American Society for Microbiology. All Rights Reserved.
BCG vaccine; culture filtrate protein 10; early secretory antigenic target 6; gamma interferon; animal experiment; animal tissue; article; bacterium culture; BCG vaccination; bovine tuberculosis; controlled study; disease severity; drug efficacy; Ethiopia; Mycobacterium bovis; newborn; nonhuman; priority journal; tuberculin test; Animals; Bacterial Proteins; Cattle; Ethiopia; Interferon-gamma; Lymphocytes; Mycobacterium bovis; Mycobacterium tuberculosis; Severity of Illness Index; Tuberculin Test; Tuberculosis Vaccines; Tuberculosis, Bovine