Threats of bioterrorism have officials in the United States on the lookout for anthrax and other disease agents. Veterinarians from the Texas Cooperative Extension Service want to assure livestock owners that cases of anthrax found this summer in Texas stemmed from natural soil-borne transmission, with no connection to any bioterrorist acts.

The Horse reported in mid-June on a small outbreak of anthrax in southwest Texas affecting horses and other animals. At press time, anthrax cases were no longer occurring in deer and other livestock, and the horse cases were limited to those reported (see article #2837 at www.thehorse.com).

Anthrax naturally occurs in Texas and other Great Plains states, and horses occasionally get the disease. The anthrax agent is a resilient spore-forming bacterium called Bacillus anthracis, which lives in the ground. Livestock ingest B. anthracis when they forage close to the ground during drought, or when they eat feed grown on infected soil. Horses seem to be more resistant to anthrax than other livestock species, such as sheep or cattle. Naturally occurring anthrax appears in Texas from late June through September and October, and outbreaks end with the start of cooler weather.

Floron C. Faries, Jr., DVM, MS, Professor and Extension Program Leader at Texas A&M’s College of Veterinary Medicine, said, “When anthrax shows up in livestock, it’s a known fact that the animals have swallowed spores from the soil—they’ve gotten the disease by way of mouth. It’s not related to bioterrorism