Suspected Botulism Outbreak Kills Dozens of Florida Horses
Preliminary evidence has suggested that botulism might be the cause of botulism may be the cause of death of approximately 100 horses at a large breeding facility in Florida housing approximately 400 mares. The horses died over a period of about 7 days, with signs of neurological disease. There are no reports of affected horses at other facilities in the area. The clinical signs in these horses and lack of evidence of another disease are strongly suggestive of botulism. This farm apparently fed the horses haylage (although some reports seem to alternate between using the words "hay" and "haylage"), which is a high-risk feed source for botulism.
In adult horses, botulism is caused by ingesting a toxin produced by the bacterium Clostridium botulinum. This bacterium will not grow in the presence of oxygen, however in can grow in conditions that are sometimes present in improperly fermented haylage and silage. As the bacterium grows, it produces botulinum toxin, one of the most potent toxins on the planet. Ingestion of botulinum toxin leads to progressive paralysis (i.e. severe weakness and flacid muslces).
Treatment of botulism is difficult and can be expensive, and the mortality rate for this disease is high. Some people choose to feed haylage and silage despite the risk of botulism. If you choose to feed haylage, silage or other high-risk feeds:
- Ensure that haylage/silage is properly prepared and stored.
- Consider vaccinating horses that are fed haylage/silage against botulism. Be aware, however, that vaccines do not protect against all strains of botulism.
- Immediately stop feeding haylage or silage if any horses show signs that could be consistent with botulism (e.g. weakness, problems eating).
Another point to add to the topic on vaccination... it's illegal to import vaccines into Canada without a valid import permit issued by the Veterinary Biologics Section of the CFIA. Since most internet distribution sites originate in the US, the chances are high that the package will be seized at the border. Permits are not issued after the fact, so once the package has been seized, it will not be allowed into the country.