lindsayH
Well-Known Member
I thought I'd share my notes from the RVC's AM lecture I attended the other day. They have been done from memory so any mistakes are mine not Richard Piercy's! If you have any questions ask, there were LOTS asked on the day so chances are someone asked it (although the answer is probably 'We don't know'!).
Aytypical Myopathy Lecture Notes
Professor Richard Piercy
What we know:
- Caused by Hypoglycin toxin found in sycamore seeds and probably other parts of the tree incl. leaves. Originally identified in American tree Box Elder another Acer. This toxin also causes Jamaican Vomiting Sickness in humans.
- Sycamore tree may not actually be in field, could be 100 yards away.
- Toxin prevents muscle cells from correctly metabolising fatty acids so muscle tissue becomes 'clogged' with fat. All body muscles affected including heart, diaphragm etc.
- Slow twitch muscle cells are more affected than fast twitch, so breeds with more slow twitch may be affected worst (eg. Arab, Spanish).
- More common after severe weather (wind/rain), due to leaves/seeds being blown from branches.
- Seen more often in horses on poor grazing with no supplementary food.
- Symptoms are lethargy, head hanging, dark urine, high heart rate, muscle trembling, reluctance to move, can resemble colic. Later, recumbency, severe muscle atrophy and pain, death. Temperature normal/low and horses often continue to eat, even if they can't stand.
- Diagnosed with blood test.
- Mortality rate of CLINICAL cases seems to be around 75%.
- Horses that survive usually make a full recovery.
Treatment:
- Fluids.
- High carbohydrate diet.
- Carnitine.
- Vitamin B2.
- Antibiotics if any secondary infections.
- Pain killers.
RP keen to stress that we don't know if all of these things actually help, but no cure at the moment so just doing what they can.
What we don't know:
- Why some horses succumb and others don't. It might be that some horses will eat the seeds and others won't.
- How common sub-clinical cases are. It is likely that this disease is more common than we think but many cases show little or no signs.
- Why other species are not affected (sheep, cows etc)
- What a toxic dose is (how much they have to eat to become ill).
- If other Acer species produce the toxin, although all cases so far appear to be related to Sycamore.
- How or why the tree produces the toxin (RP is in contact with Sycamore experts who are also interested in this disease).
- Why there has been such a big increase in cases.
- Exactly what causes Spring cases, although RP believes it to be horses eating Sycamore seedlings.
What owners can do:
- Avoid grazing horses in fields near Sycamores in Autumn, until leaves/seeds have rotted.
- If horses cannot be moved, fence off worst affected areas and provide plenty of hay.
- Bringing in overnight may help, it is possible horses eat seeds in the dark when they can't see them.
- In Spring, keep horses away from areas with Sycamore seedlings until you can mow/weed kill them.
- Keep water troughs free of Sycamore seeds/leaves in case toxins leach into water.
- If you suspect your horses has AM call vet, move it as little as possible, if it is cold rug it well to prevent shivering, keep it calm/quiet and offer hay.
- If your horse is at high risk (horse on yard/locally has AM, field has a Sycamore) it can be blood tested to check for the disease. An early symptom may be lethargy so if your horse is high risk and seems lethargic you should definitely get blood test.
Aytypical Myopathy Lecture Notes
Professor Richard Piercy
What we know:
- Caused by Hypoglycin toxin found in sycamore seeds and probably other parts of the tree incl. leaves. Originally identified in American tree Box Elder another Acer. This toxin also causes Jamaican Vomiting Sickness in humans.
- Sycamore tree may not actually be in field, could be 100 yards away.
- Toxin prevents muscle cells from correctly metabolising fatty acids so muscle tissue becomes 'clogged' with fat. All body muscles affected including heart, diaphragm etc.
- Slow twitch muscle cells are more affected than fast twitch, so breeds with more slow twitch may be affected worst (eg. Arab, Spanish).
- More common after severe weather (wind/rain), due to leaves/seeds being blown from branches.
- Seen more often in horses on poor grazing with no supplementary food.
- Symptoms are lethargy, head hanging, dark urine, high heart rate, muscle trembling, reluctance to move, can resemble colic. Later, recumbency, severe muscle atrophy and pain, death. Temperature normal/low and horses often continue to eat, even if they can't stand.
- Diagnosed with blood test.
- Mortality rate of CLINICAL cases seems to be around 75%.
- Horses that survive usually make a full recovery.
Treatment:
- Fluids.
- High carbohydrate diet.
- Carnitine.
- Vitamin B2.
- Antibiotics if any secondary infections.
- Pain killers.
RP keen to stress that we don't know if all of these things actually help, but no cure at the moment so just doing what they can.
What we don't know:
- Why some horses succumb and others don't. It might be that some horses will eat the seeds and others won't.
- How common sub-clinical cases are. It is likely that this disease is more common than we think but many cases show little or no signs.
- Why other species are not affected (sheep, cows etc)
- What a toxic dose is (how much they have to eat to become ill).
- If other Acer species produce the toxin, although all cases so far appear to be related to Sycamore.
- How or why the tree produces the toxin (RP is in contact with Sycamore experts who are also interested in this disease).
- Why there has been such a big increase in cases.
- Exactly what causes Spring cases, although RP believes it to be horses eating Sycamore seedlings.
What owners can do:
- Avoid grazing horses in fields near Sycamores in Autumn, until leaves/seeds have rotted.
- If horses cannot be moved, fence off worst affected areas and provide plenty of hay.
- Bringing in overnight may help, it is possible horses eat seeds in the dark when they can't see them.
- In Spring, keep horses away from areas with Sycamore seedlings until you can mow/weed kill them.
- Keep water troughs free of Sycamore seeds/leaves in case toxins leach into water.
- If you suspect your horses has AM call vet, move it as little as possible, if it is cold rug it well to prevent shivering, keep it calm/quiet and offer hay.
- If your horse is at high risk (horse on yard/locally has AM, field has a Sycamore) it can be blood tested to check for the disease. An early symptom may be lethargy so if your horse is high risk and seems lethargic you should definitely get blood test.
