The Mycobacterium tuberculosis complex consists of the closely related organisms M. tuberculosis, M. africanum, M. bovis, M. bovis BCG, and a few additional species. Mycobacterium bovis Calmette-Guerin (BCG) is a live, attenuated strain of M. bovis. In addition to its well-known use as a vaccine against tuberculosis overseas, BCG is still the most effective agent for the treatment of transitional cell carcinoma of the bladder. Patients with BCG disease are typically first encountered by a primary care or emergency room physician, sometimes months or years after the last exposure to BCG. M. bovis causes disease in cattle, deer and other mammals. In humans, consumption of unpasteurized infected cows milk products can cause infection, as well as transmission from an infectious TB patient harboring M. bovis bacteria