Mycobacterium bovis DNA Detection in Colostrum as a Potential Indicator of Vaccination Effectiveness against Bovine Tuberculosis

Bovine tuberculosis (bTB) remains a problem onmany dairy farms inMexico, as well as a public health risk. We previously found a high frequency ofMycobacterium bovisDNA in colostrum from dairy cows using a nested PCR to detectmpb70. Since there are no reliable in vivo tests to determine the effectiveness of boosterMycobacterium bovis BCG vaccination against bTB, in this work we monitoredM. bovisDNA in colostrum by using this nested PCR. In order to decrease the risk of adverse reactions in animals likely containing viableM. bovis, a single application of BCG and a subunit vaccine (EEP-1) formulated withM. bovis culture filtrate proteins (CFP) and a copolymer as the adjuvant was performed in tuberculin skin test-negative cattle (TST), while TST reactor animals (TST) received EEP-1 only. Booster immunization using EEP-1 was applied to both groups, 2 months after primary vaccination to whole herds and 12months later to lactating cows. Colostrum samples were collected from 6 farms where the cows were vaccinated over a 12-month period postvaccination and, for comparison, from one control farm where the cows were not vaccinated with comparable bTB prevalence. We observed an inverse relationship between the fre-quency ofM. bovisDNA detection and time postvaccination at the first (P< 0.001) and second (P< 0.0001) 6-month periods. Additionally, the concentration of gamma interferon (IFN-) was higher inmpb70 PCR-positive colostrum samples (P 0.0003). These results suggest thatM. bovisDNA frequency in colostrum could be a potentially useful biomarker for bTB vaccin