Equine Science Update
Reports from the world of  equine research.
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Equine Atypical Myopathy (EAM) is an emerging disease of horses, which usually results in death.

It tends to affect young horses up to three years old (especially those about 18 months old). Horses that are in poor condition and not in regular work seem to be more at risk of the disease, as do those that have not been vaccinated or dewormed.

The last few months of 2009, Western Europe experienced the largest ever series of cases of the disease,
Written by Mark Andrews. Published online 24.04.10
 © Copyright Equine Science Update  2010
Atypical myopathy -
possible cause found
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The last few months of 2009 saw the highest number of cases ever recorded in Western Europe, according to the Atypical Myopathy Alert Group. So far in 2010, 30 suspected cases had been reported to the University of Liege, including 23 in France. Up to 20th April

So far the cause is not known. Analysis of records of clinical cases suggest that the most likely cause is a toxin (from a plant, fungus or bacterium.)

Now researchers at the University of Bern, Switzerland, have identified a possible culprit.

Dr Lucia Unger-Torroledo and others in the Equine Clinic, together with colleagues from the Departments of Anatomy and Veterinary Bacteriology, have found evidence to implicate a bacterial toxin.

They investigated the possibility that the lethal toxin of Clostridium sordellii was involved. This toxin is known to cause severe muscle damage in mice.

The researchers examined heart and skeletal muscle samples from horses affected with Atypical Myopathy using transmission electron microscopy. They found that the changes that were present were similar to those found in mice affected by the toxin.

They also used immuno histochemistry staining techniques to show that the lethal toxin of Clostridium sordellii was present in the muscle fibres of affected animals. Antibodies from horses with Equine Atypical Myopathy and antibodies to the lethal toxin of Clostridium sordellii both bound to muscle fibres taken from horses affected with EAM.

In contrast, neither of the antibodies attached to normal horse muscle fibres or to muscle fibres taken from horses with other types of muscle disease.

The scientists concluded that there is evidence that the lethal toxin of Clostridium sordellii plays a role, either as a trigger, or even as a lethal factor, in Atypical Myopathy.

The work has been accepted for publication in the scientific journal Veterinary Microbiology, and is currently available on line. An abstract is available on PubMed.

For more details see:

Lethal toxin of Clostridium sordellii is associated with fatal equine atypical myopathy.
Unger-Torroledo L, R Straub, AD Lehmann, F Graber, C Stahl, J Frey, V Gerber, H Hoppeler, O Baum.
Vet Microbiol. 2010 Feb 1 (e pub ahead of print)

Semimebranosus muscle of EAM affected horse stained to show the presence of  the lethal toxin of Clostridium sordellii  
Photo courtesy Dr Lucia Unger-Torroledo.