Anthrax is a rapidly developing, acute or sub-acute, fever-producing, infectious disease of all warm-blooded species, including humans. It is a dangerous, reportable disease that when suspected in an animal should be brought immediately to the attention of a veterinarian. Anthrax outbreaks are commonly found in regions with alkaline (basic) soil, such as the Great Plains states (North Dakota to Texas) and the Intermountain Basin states (Nevada and Utah). Field outbreaks of anthrax in these areas are more prevalent than in other geographical parts of the United States.
Its infectious nature was first demonstrated in 1836, and the causative bacteria, Bacillus anthracis, was first cultivated by Robert Koch in 1876 and Louis Pasteur in 1877. The pioneering work of Pasteur showed that by changing the bacteria Bacillus anthracis, a vaccine could be produced to protect susceptible animals.
Anthrax in the horse is characterized by a high fever (up to 107°F) and a quick death. Rigor mortis is absent or incomplete in an anthrax carcass. Horses are mildly resistant, therefore cases might be seen before they die. In cattle and sheep, outbreaks declare themselves with dead animals. Horses frequently have ventral edema (swelling), are fevered, and are obviously “sick.” Horse carcasses often have dark blood oozing from the mouth, nostrils, and anus. Diagnosis can be based on these clinical signs, but laboratory confirmation is based on finding Bacillus anthracis in a blood sample or blood culture.
Time is of essence in diagnosing a horse herd with anthrax—the “quick killer.” Although blood cultures take longer for results, the