Attention! This is a potentially life-threatening condition for your horse. Time is of the essence, contact your veterinarian immediately.Find a Vet


Anthrax is a highly contagious, rapidly fatal zoonotic disease, caused by the spore-forming bacteria Bacillus anthracis. Anthrax is an OIE-listed disease, which is found worldwide, occurring on all continents except Antarctia. It is typically a disease of ruminants and humans.

B. anthracis is shed by its infected host onto the ground, and sporulates when exposed to air. These spores can live in the soil for decades and appears brown and powdery---similar to cinnamon or coca. Bacilli exhibit an array of physiologic abilities that allow them to live in a wide range of habitats, including many extreme habitats such as desert sands, hot springs, and Arctic soils.

Immunization has led to a global decline in livestock anthrax cases in any parts of the world. Outbreaks are often associated with heavy rainfall, flooding, or drought.

Clinical signs differ depending on the route of transmission of the spores. Inhalation of the spores is the most serious type of infection. Affected animals usually die within 1–3 days, but some animals can survive for up to a week.

Transmission to horses is generally caused by ingestion of the spores while grazing, browsing, or drinking. Other, less likely ways are through inhaling dust containing the spores, direct animal-to-animal contact, biting flies, and human-associated malicious attempts.

Incubation Period
The incubation period is generally 1–7 days, but spores can germinate in the lungs up to six weeks post-infection.


Black blood from the mouth, nostrils, and found in droppings
Muscle tremors
Difficulty breathing
Swelling of the neck, head, limbs, and/or abdomen
Sudden death


  • History
  • Clinical signs
  • Bacterial culture
  • skin hypersensitivity test using AnthraxinT



Report disease: Anthrax is a reportable disease, meaning that if you suspect that your horse has this disease, by law you need to report it to your veterinarian, or a state or federal veterinarian.Antibiotics


  • Proper disposal of dead animals
  • Proper cleaning and disinfection to control insects and rodents
  • Vaccination in endemic areas


Essentially any of the forms of anthrax is treatable if the diagnosis is made early enough and with the appropriate supportive therapy.

Scientific Research

General Overviews

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Causative agent