Anthrax is an acute, febrile infection that has a rapidly fatal course. It is one of the oldest and most destructive disease of livestock and has caused the loss of many human lives as well. The specific case of anthrax is a micro-organism known as Bacillus anthracis. Anthrax is a naturally occurring disease with worldwide distribution. Though it can occur anywhere it is most commonly reported in the US in the lower Mississippi river basin, coastal Louisiana and Texas, and some areas of the Great Plains. Though horses are more resistant than other herbivore, they can contract the disease.

By mid-July 2001, seven ranches in Val Verde, Uvalde, and Edwards had laboratory confirmed cases of anthrax in deer and livestock, including two horses. Private veterinary practitioners and ranchers in these counties and Real, Kinney and western Bandera Counties also had reported losses due to the disease. A "significant" white-tailed deer death loss was reported along in southeast Edwards and southwest Real Counties.

It is caused by Bacillus anthracis, a spore-forming bacterium that can remain alive, but dormant in the soil for many years. The bacteria can "bloom" and contaminate surface soil and grass after periods of wet, cool weather, followed by several weeks of hot, dry conditions. Grazing animals--such as cattle, sheep, goats, exotic and domestic deer, and horses--ingest anthrax bacteria when they consume contaminated grass. Domestic and wild swine are fairly resistant to anthrax and although they may become ill, some of these animals recover fully.

Anthrax can occur anywhere but is usually seen as small pockets of outbreaks. Anthrax outbreaks depend on two factors working together: the presence of the spores in the soil . . . and suitable weather conditions. Outbreaks usually end when cool weather arrives and the bacteria become dormant. An outbreak may occur one year, but not the next. Death loss may occur in one pasture, while animals nearby remain healthy. During an outbreak, white-tailed deer often suffer the most from the disease and may be responsible for the spread. An increase in deer deaths may be a harbinger of an outbreak.