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  Discussion on Equine botulism and acute pasture myodystrophy
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Moderator:
DrO

Posted on Monday, Nov 27, 2006 - 10:28 am:

As this disease is being diagnosed more often in Europe it should be considered anywhere these symptoms crop up without a well defined cause.
DrO

Schweiz Arch Tierheilkd. 2006 Oct;148(10):553-9.

Equine botulism and acute pasture myodystrophy: new soil-borne emerging diseases in Switzerland?

Gerber V, Straub R, Frey J.
Equine Clinic, Department of Clinical Veterinary Medicine, Vetsuisse-Faculty University of Berne, Switzerland.

In Switzerland, the incidence of equine botulism and acute pasture myodystrophy have remarkably increased in the last five years. Equine fodder-borne botulism in Europe is most likely caused by Clostridium botulinum types C and D that produce the toxins BoNT/C and BoNT/D. Horses showing signs suggestive of botulism (muscle weakness and tremors, reduced tongue tone, slow chewing, salivation and difficulties swallowing, DrOoping eyelids, mydriasis), especially patients that have fed on suspect fodder (mostly haylage), must be treated with anti-serum as soon as possible.They also need intensive care, which is often difficult to provide and always expensive in the face of a guarded to poor prognosis. Therefore, prevention (high standards of forage quality and vaccination) is all the more important. Pasture myodystrophy is an acute disease with signs of rhabdomyolysis and lethality rate over 90%. It affects grazing horses under frosty, windy and rainy conditions. Preliminary results indicate that Clostridium sordellii and Clostridium bifermentans producing lethal toxin may play a role in pasture myodystrophy. Our efforts concentrate on developing a new subunit vaccine for equine botulism and understanding the ethiology and pathogenesis of pasture myodystrophy with the goal of improving prevention against these highly fatal diseases that present a significant risk to our horse population.
New Member:
lsr1950

Posted on Sunday, Oct 4, 2009 - 2:32 pm:

We lost 2 mules in May of this year following a frost. Symptoms included loss of appetite, heavy DrOoling, lethargy, weakness and and inability to stand within 12 to 24 hours and we euthanized the younger animal within 12 hours and the older at 24 hours. The older mule appeared to be slightly swollen in her mid section, but continued to have an appetite and eat hay and on the advice of the vet, we put her in a stall overnight. I checked her every hour until 11:00 PM and each time she was recumbent and eating hay, but would immediately stand up when I spoke to her.
The next AM, I found her unable to get up or raise her head, with hay clenched in her mouth. She was able to nicker to me. Vet came and started IV fluids, said gut sounds were very diminished and her respirations were very labored but within normal resting rate. Made the decision to euthanize within an hour based on vet's opinion that she wasn't going to make it.
We took her body to the state lab and report was negative for damage to internal organs including CNS. They suggested botulism or ingestion of toxic substance based on history.
We lost another horse with same symptoms Oct 1. This time the vet tried DMSO and steroids but ineffective. Horse died in the night and seemed to have swelling of face and neck.
I wonder if our animals suffered from this myodystrophy and what we need to do to protect our remaining horses. I also wonder if they might have gotten botulism from eating dirt around our barn while they were put up during the day in our dry lot.
Moderator:
DrO

Posted on Monday, Oct 5, 2009 - 8:01 am:

Welcome lsr1960,
My condolences on your recent lost. Several different diseases are discussed above but what they have in common is that they are caused by the toxins produced by bacteria of the genus Clostridium. The different toxins have different effects but all are very lethal. There is much about the case you describe that would be consistent with toxicoinfectious clostridium toxin death.

The reason frost is involved is that it can result in large clumps of dead forage that the clostridia can reproduce in. Is there a source of spoiled forage that your mules are exposed to? Is there a reason to suspect the dirt around your barn has been heavily contaminated by botulinum spores? For more thoughts on the life cycle and ways horses contract botulism see Diseases of Horses » Nervous System » Incoordination, Weakness, Spasticity, Tremors » Botulism Poisoning, Shaker Foals.
DrO
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