November 28, 2019

A modified version of the BCG vaccine for tuberculosis (TB) may allow cattle to be vaccinated against TB for the first time, reported New Scientist.

Currently, cattle infected with TB are culled, along with other livestock in the vicinity that could spread the disease.

Johnjoe McFadden, team leader of the study at the University of Surrey, United Kingdom said the modified vaccine has been tested in guinea pigs with positive results, and it should work on cattle. They will begin tests on cattle once they obtain funding.

The standard BCG vaccine used on humans is banned for use on cattle in some countries, as only 70% of cattle are protected from TB after vaccination.

Standard tests, in which dead TB bacteria is injected into the skin, cannot differentiate vaccinated and infected cattle as both react to the diagnosis in the same way. This makes it difficult to detect the disease among a herd if the standard BCG vaccination was used.

The team led by McFadden overcame the problem by deleting six protein-coding genes from the BCG vaccine strain. TB-infected cattle will elicit a response when injected with these six proteins into their skin, but vaccinated cattle will show no response. When the new skin test is combined with the modified vaccine, it is easier to detect TB-infected cattle.

The study was conducted with research organisations from India, where cattle infected with TB is an issue. Hindus consider cattle to be sacred, so culling is prohibited.

McFadden said if cattle vaccination was possible, the current practice of culling wild badgers to stop the spread of TB can be stopped (/contents/10-30-2019/8c1e9d79-eda3-4aa5-8114-4b4f5b51830c-5061.html). Studies have shown that culling wild badgers may be counterproductive to halting the spread of the disease.

There was a similar study conducted to differentiate vaccinated and infected livestock, centred on the dissimilarities between TB and the standard BCG strain. McFadden said these differences are harder to detect and using his team’s solution is much more effective.

-  New Scientist