Hypersensitivity

 Following the disqualification of Canadian show jumper from this summer’s Olympics for limb hypersensitivity, Horse and Hound reviewed why hypersensitivity is such a delicate issue.

The term ‘hypersensitivity’ refers to a heightened response by a horse to pressure applied to a limb or part of a limb. It is something that has been in international showjumping for years, with no real way of diagnosing it. Cases of rapping – where a pole is raised manually to hit the horse’s legs as it jumps a fence, scaring it into jumping higher and causing its legs to be painfully sensitive. There are other ways to heighten a horse’s response to touching poles.

Capsaicin – an ingredient in chili peppers- can allegedly used to make horses’ legs over-reactive to touch and thus encourage them to jump higher. In addition, there are many ‘home methods’ that are used by different trainers.

Since 2009, more than 3000 examinations have been carried out globally for hypersensitivity. At London 2012, there was on positive result, for the Canadian showjumper Victor, ridden by Tiffany Foster. The gelding was found to have an area of hypersensitivity on the front of the coronary band on a forelimb and his rider was disqualified.

Accidental hypersensitivity – The difficulty for testing for hypersensitivity is that the examination does not distinguish between a abnormally sensitive leg that might be caused by a minor wound or a skin infection, or one that might be caused by deliberate malpractice using a banned, foreign substance. By the nature of showjumping, horses that are frequently jumping fences over 5ft are likely to pick up the odd bump and scratch, without any deliberate malpractice. It is rare that such accidental wounds such as insect bites will by hypersensitive, but it is not impossible to rule them out. The harsh reality is that any horse testing positive for limb hypersensitivity – intentionally inflicted or not – should be disqualified from competition.

Demystifying hypersensitivity – There are a number of misconceptions about hypersensitivity testing. Some of the most common questions are: ‘When my horse was examined for hypersensitivity, why was he not trotted up to see if he was lame?’ A trot-up plays no part  in a  hypersensitivity examination. A hypersensitive horse will frequently show no sign of lameness in the affected limb. A leg can be painful when pressure is applied to it, and hence hypersensitive without a horse being lame. ‘Above what temperature is a horse deemed hypersensitive?’ There is no specific rule for this as limb temperature can vary a lot naturally. Thermography is used to compare the patterns of temperature between the limbs within the same horse. ‘ Surely any horse will respond if you poke his leg enough times?’ The clinical hypersensitivity examination does not involve poking the leg, rather palpating it in a controlled and sympathetic fashion. A horse that is truly hypersensitive tends to get increasingly response to palpation, whereas one that is not usually becomes less reactive the more he is touched.

So what does the hypersensitivity test involve? The examination contains two elements:

1) A thermal imaging camera is used to map the surface temperature of the leg. The actual limb temperature can be very variable and is affected by other factors such as environmental temperature, whether the horse has recently been wearing bandages or has had his legs washed – or even something as simple as whether the leg has even covered in stable bedding. The specific temperature of the leg is not relevant. The important issue is whether the temperature of a pair of limbs an the heat distribution within them is similar.

2) Clinical examination. The lower limbs are carefully palpated ( examined by touch and not prodded) in a repeated manner to asses their sensitivity. Where the thermal imaging apparatus is very sensitive, it is the clinical part of the examination that carries the greater weight.

It is impossible for the horse to be designated as hypersensitive based on an abnormal response to palpation without a supporting thermal image. The same decision could not be made solely on the bases of abnormal thermography. If the examining vets consider a horse to be hypersensitive, a second examination will then be performed involving the foreign vet delegate, which is observed by a member of the ground jury. If it is a unanimous view that the horse is still hypersensitive they will recommend to the ground jury that the horse is disqualified.

Past Hypersensitivity Cases

McLain Ward and Sapphire, Geneva, April 2010

The American rider (right) was disqualified from the Rolex World Cup finals in Geneva in 2012 when leading because his horse Sapphire failed a hypersensitivity test. Sensitivity was found in her near foreleg before the second World Cup round, but she was deemed fit to compete at the time. The FEI re-examined the mare after the round took place and this time found her unfit to take any further part, due to the level of hypersensitivity being shown. There was no indication or evidence of malpractice or wrongdoing and there mare did not test positive to any banned or controlled substance.

Denis Lynch and Lantinus 3, Aachen, July 2012

Denis was eliminated midway through the Aachen Nations Cup at the beginning of July  – this was the third time one of his horses had tested positive in a 12 month period – and it ruled him out of the Irish team for London 2012. A statement given by Denis at the time read ; ‘ At no stage was there any inference that the hypersensitivity was anything other than natural occurring. I feel this is very important to clarify and I would also like to state for the record that I fully support all measures regarding hypersensitivity implemented by the FEI’

In my opinion, Horse and Hound have got this article spot on, giving it the title ‘a delicate issue’. By reading this article it seems that when a horse is deemed hypersensitive, it could easily be a wrong judgement. Through my care of my own horses, throughout the summer the temperature of their legs is always fluctuating due to work, whether they have been washed, fly bites, whether they have laid down on that leg, etc. The idea of testing for hypersensitivity is a breakthrough in the showjumping world, however maybe there should be further work to developing a more reliable way of testing for hypersensitivity? An interesting issue that has now got me thinking!

Hope you enjoyed this article, will be another next week :)

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