Anthrax Update

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

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."

He said that terrorist acts of spreading the disease in humans would probably involve inhalation of aerosol anthrax, a very different method than the natural ingestion of the spores. It has been reported that humans affected in the recent anthrax scare have contracted the disease both cutaneously (on the skin) and by inhalation.

Human inhalation and cutaneous infection has occurred naturally in the past, according to Bruce Lawhorn, DVM, a professor at Texas A&M University and a Texas Agricultural Extension Service veterinarian. Anthrax historically has been referred to as "wool-sorter’s disease." Wool and mohair factory personnel sometimes contracted inhalation anthrax (rarely) and cutaneous anthrax (more commonly). Sheep and goat hides often were contaminated by dirt containing spores of anthrax; workers would inhale this dirt and get it in their wounds.

"Cutaneous anthrax has occured sporadically in the past (in humans)," said Lawhorn. "Last summer there was one confirmed case of (cutaneous) anthrax in a human that skinned out an anthrax-contaminated carcass. He was treated and recovered. The bottom line is that there are not many naturally occurring (cutaneous) anthrax cases, even in those endemic Texas counties where a lot of people are potentially exposed."

Anthrax Vaccine Note

In the face of the anthrax scares, "There has not been an increase in anthrax (livestock) vaccination sales," said Michael D. Piontkowski, DVM, Director of Technical Services at Colorado Serum Company, which manufactures and distributes the anthrax vaccine for livestock. "We are not noticing an increase in sales, especially in areas that don’t normally deal with anthrax in livestock."

Horse owners who would like to learn more about anthrax in livestock can visit a resource provided by The Texas Cooperative Extension Service at, or you can refer to the November issue of The Horse, "Anthrax Affects Everyone," article #2859 at

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More

Free Newsletters

Sign up for the latest in:

From our partners