Obviously the equilibrium between man and the tubercle bacillus is very precarious. If war can so rapidly upset it, other unforeseen events might also cause recurrences of the tuberculosis epidemic in the Western World. (Dubos and Dubos, 1952, p. 196)
In the early 1900s the threat of tuberculosis caused by Mycobacterium bovis (one of three species in the Mycobacterium tuberculosis complex) was also addressed. The Tuberculosis Eradication Division was organized within the U.S. Department of Agriculture Bureau of Animal Industry in 1910 to organize a campaign for the control and eventual elimination of M. bovis in cattle to eliminate the threat to humans. This program required that all cattle herds be systematically tuberculin skin tested, that herds with infected cattle be slaughtered (with an indemnity paid to the owner), and that the premises be cleaned and disinfected after the infected animals were removed. This led to a very rapid reduction in the incidence of bovine tuberculosis. Currently, the positive reaction rate among cattle is less than 2 per 1,000 animals, with many of those reactions believed to be false positive. This program has also effectively eliminated tuberculosis in humans because of infection with M. bovis. In the late 1970s, an average of only 26 M. bovis isolates a year were reported among isolates sent to the Centers for Disease Control (now known as the Centers for Disease Control and Prevention [CDC]); this represents less than 1 percent of the total isolates sent to the CDC each year, and about 0.1 percent of the total number of tuberculosis cases reported each year (Good, 1980). The few new infections that occur seem to be associated with pediatric exposure to infected milk products outside the United States (primarily Mexico) (Danker et al., 1993) and from occupational exposures to infected game and zoo animals (Dalovisio et al., 1992; Fanning and Edwards, 1991; Nation et al., 1999; Thompson et al., 1993). Because of the low risk of disease following infection (Magnus, 1966; Moda et al., 1996), the occupational exposures are also unlikely to result in a barrier to elimination.
Countrywide mortality data for the United States were not available until 1933. Before that time data were collected from state “death registra