Tuberculosis of Cattle

All States are now in the modified-accredited status; that is, in no State is there an incidence of more than 0.5 percent of tuberculous infection in the cattle population. But some traces of infection remain in almost every State—it is impossible to give the tuberculin test annually to every animal in the country. A way of discovering foci of infection has been worked out with the Federal Meat Inspection Division. When postmortem examinations in abattoirs show animals to be tuberculous, their origin is traced, and the disease in the infected herd is eradicated by test and slaughter. The method, together with general testing, is slowly reducing bovine tuberculosis to the vanishing point.

Anthrax

Anthrax, one of the oldest and most destructive diseases of animals and man, is still a problem in some parts of the United States.

We obtained considerable necessary information on the history and incidence of anthrax in recent studies. Outbreaks of a disease believed to be anthrax occurred in Pennsylvania as early as 1834, in Louisiana in 1835, and in Mississippi in 1836. Outbreaks in New York were recorded in 1881, in Vermont and Massachusetts in 1887, and in California in 1888. Infected areas still exist in those States. Between 1915 and 1945 there was a gradual increase in the territory involved, with outbreaks of anthrax in livestock in 438 counties in 45 States. Large areas of recognized infection exist in South Dakota, Nebraska, Arkansas, Mississippi, Louisiana, Texas, and California; small areas exist in Vermont, New Jersey, Delaware, Utah, Nevada, and Oregon. The disease in those areas can be largely controlled by annual preseasonal vaccination, strict quarantine, and prompt disposal of all infected material during outbreaks.

Experimental studies, observations in the field, and reports from practicing veterinarians indicate that anthrax spore vaccine of the proper strength administered between layers of skin is an effective type of preventive vaccination. It is gaining in favor in many parts of the country, and is widely used in Texas, Louisiana, Nebraska, and South Dakota;

Anthrax still takes its toll of livestock in 43 States. Virulent outbreaks occur in South Dakota, Nebraska, Arkansas, Mississippi, Louisiana, Texas, and California.

In Nebraska, South Dakota, and small sections of Iowa and Minnesota, the number of herds quarantined for anthrax declined from 1,592 in 1937 to 20 in 1945. On the Indian reservations in South Dakota, where more than 45,000 cattle were vaccinated with intradermal spore vaccine from 1939 to 1945, only 16 animals were lost from anthrax.

Considerable information was obtained from recent studies on the tenacity of B. anthracis and its spores. Dry anthrax spores were killed by dry heat at 149° to 150° C. in 60 minutes, but not in 30 minutes. Spore suspensions in distilled water were destroyed in 3 to 5 minutes by vigorous boiling, in 5 to 15 minutes at 100° to 101° C., and in 5 to 15 minutes in the autoclave at 15 pounds pressure (120° C.), while several strains resisted heating at 90° to 91° C. for 60 minutes. Dry spores in dried blood on cotton swabs from field cases held in glass vials at 25° to 30° C. were both viable and virulent after storage for 8 years. Suspensions of spores in normal saline resisted rapid shell freezing at —72° C. to —78° C. and thawing at 37° C. for 45 successive times. Viable anthrax spores were recovered from the vapors of heated anthrax-spore suspensions and from the distillate of anthrax-spore suspensions.

In the unopened carcasses of guinea pigs dead of anthrax, held at 28° to 30° C. for 80 hours, B. anthracis could not be isolated from the blood, but when held in the ice box at 5° to 10° C. B. anthracis could be recovered after 4 weeks in storage.

The spores that formed from vegetative forms in bone marrow and muscle tissue from guinea pigs dead of anthrax were still viable after the decomposing tissues had been held 6 months at room temperature (28° to 30° C).