Research Confirms BCG Vaccine's Protective Benefits in Ethiopian Cattle

The Bacillus Calmette-Guerin (BCG) vaccine can reduce the transmission of bovine tuberculosis (bTB), and routine vaccination of cattle could be used to substantially eliminate the disease within the Ethiopian dairy sector, according to a new study by Abebe Fromsa and colleagues. Although the vaccine has been used to protect livestock from bovine tuberculosis, its effectiveness has not been quantified until now. Vaccination offers a hopeful solution for containing the disease in low-and middle-income countries, where the method of test-and-slaughter of livestock practiced in industrialized countries is less economically feasible. The natural transmission experiment performed by Fromsa et al. in herds of cattle allowed the researchers to directly measure the rate of bovine tuberculosis transmission to and from vaccinated and unvaccinated calves over a one-year exposure period to the disease. The results suggest that the vaccine is more effective at reducing disease transmission from vaccinated animals than directly protecting the animals against infection. Overall, the findings suggest that BCG vaccination could reduce disease transmission by 89%. Further modeling by the researchers indicates that consistent vaccination could bring the disease under control in Ethiopian dairy cattle within a few decades. "Our studies suggest that the effectiveness of BCG in the field is likely to be greater and the risks lower than previously understood and we provide key missing evidence of the potential benefits of a BCG-vaccination based approach to accelerate control of bTB in regions where the disease remains endemic," they write. Anita L Michel discusses the findings in a related Perspective.