Botulism in horses: Veterinarians should be cognizant in their diagnosis

Botulism in horses: Veterinarians should be cognizant in their diagnosis

Knowing what to look for and being diligent in gathering the patient's history will help diagnose this often overlooked condition.
Oct 01, 2013

Treatment options

The antitoxin treatment—available commercially now—is essential, and the sooner the horse gets it, the better. Veterinarians who reside in endemic areas should make a plan to get plasma almost immediately for an affected horse, Johnson advises. She recommends either having a unit on hand in the freezer at the practice or being close to a clinic that has it.

"If there is no available plasma, even a shipment overnight often will not suffice," says Johnson. "It needs to be available within a few hours for the proper recommended treatment."


Only one USDA-approved vaccine against equine botulism is available in the United States—a killed (toxoid) vaccine directed against C. botulinum type B (BotVax B—Neogen Corp.). The initial series consists of three doses administered at four-week intervals, with subsequent yearly boosters. Pregnant mares should receive their primary series and then be revaccinated four to six weeks before foaling.

Passively acquired maternal antibodies do not appear to interfere with the foal's serologic response, so foals may have their primary series started as early as 2 weeks of age, although it is more commonly started at 1 to 3 months of age. Unfortunately, there are no vaccines for type A or C.1


1. Johnson AL. Advances in the diagnosis and treatment of botulism, in Proceedings. ACVIM Forum. Seattle, Wash.; June 2013.

Suggested Reading

1. Johnson AL, McAdams SC, Whitlock RH. Type A botulism in horses in the U.S: a review of the past ten years (1998-2008). J Vet Diagn Invest 2010;22(2):165-173.

2. Johnson AL, Sweeney RW, McAdams SC, et al. Quantitative real-time PCR for detection of the neurotoxin gene of Clostridium botulinum type B in equine and bovine samples. Vet J 2012;194(1):118-120.

3. Pellet S. Learning from the past: historical aspects of bacterial toxins as pharmaceuticals. Curr Opin Microbiol 2012;15(3):292-299.