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Anthrax is a serious and rapidly fatal septicemic disease caused by proliferation and spread of the vegetative form of Bacillus anthracis in the body. Infection is acquired though ingestion, inhalation or contamination of wounds by soil-borne spores of the organism. Anthrax is encountered only in limited geographic areas where alkaline soil conditions favor survival of the organism. (View map of U.S. outbreaks.) Vaccination is indicated only for horses pastured in endemic areas.


The only vaccine currently licensed for use in horses is a live Sterne strain, non-encapsulated spore-form. The vaccine has been shown to be effective; however, vaccination of pregnant mares is not recommended. Adverse reactions to the vaccine have been reported in young, and miniature horses. Local swelling may occur at the injection site, most of which resolves within a few days.

Appropriate caution should be used during storage, handling and administration of this live bacterial product. Consult a physician immediately if human exposure to the vaccine occurs through accidental injection, ingestion, or otherwise through the conjunctiva or broken skin.

Antimicrobial drugs should not be given concurrently, as this may interfere with adequate response to the vaccine.

Vaccination Schedule:

  • Adult horses previously vaccinated against anthrax:  Annual vaccination.
  • Adult horses previously unvaccinated or of unknown vaccinal history:  Administer a primary series of 2 subcutaneous doses of vaccine with a 2 to 3 week interval between doses. Vaccinate annually thereafter.
  • Pregnant mares: Not recommended.
  • Foals: There is no specific information available regarding the vaccination of foals against anthrax.