Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015

Hypoglycin A (HG) appears to cause atypical myopathy (AM), but to our knowledge, detection of HG in affected and unaffected horses and concurrently in plants that they were exposed to has not previously been reported.

To investigate HG in samples from horses exposed to Acer pseudoplatanus (European sycamore maple) and in such plant material, at the time of clinical cases of AM in the herd.

Cross-sectional study.

Blood was collected from 2 horses with AM and 22 clinically healthy co-grazing horses in 2 Swedish farms within one week of onset of signs (May 2014) and one month later, after horses were moved to other pastures. Ten healthy control horses from unaffected farms were sampled once. Samaras, seedlings, flowers and leaves from Acer pseudoplatanus and from Acer platanoides L (Norway maple) were collected from affected pastures. Hypoglycin A was analysed using chemical derivatisation with dansyl chloride (DNS) and ultra high performance liquid chromatography-tandem mass spectrometry. Hypoglycin A was detected as derivatised compound HG-DNS [M+H]+ with selected reaction monitoring.

Hypoglycin A was detected in the horses affected with AM, and also in 20 out of 22 co-grazing horses. One month later, a surviving case horse and 9/20 co-grazing horses were still positive for HG. Controls from other farms were negative for HG. Hypoglycin A was detected in plant material from Acer pseudoplatanus, but not from Acer platanoides L.

Horses grazing in pastures with HG-containing Acer pseudoplatanus were positive for HG in blood, and some showed severe signs of myopathy. Ethical animal research: Ethical consent for blood sampling was granted (C113/11) and horse owners gave their informed consent to inclusion of horses in the study.

National Veterinary Institute, Sweden. Competing interests: None declared.