Show Notes
Ep.15 Show Notes
In this Skin Flints episode, the team were delighted to host one of the giants of the equine world - the brilliant Derek Knottenbelt (or Knotty, as he is also known).
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Chapter one: Knotty
(03:49) Sue introduces Derek Knottenbelt who gives his background in the industry and his practical emphasis.
(05:09) Sue asks Derek "what is a sarcoid?". He describes it as a reactive skin tumour – so skin cancer is the best way to think about it and not viral as it has been before which has resulting in an incorrect approach; a multi-morphology skin tumour affecting all equid species and continuing to puzzle the scientific world.
(07:00) Sue asks whether it can be contagious given it is a tumour and Derek says that it is his contention that it is transmissible with circumstantial evidence to suggest this, but the mechanism for this is very little understood – it has some relationship with the bovine papilloma virus.
(08:06) Sue asks flies are spreading this and Derek says it is – where sarcoids occur tend to be where the skin is thin – where flies can feed with impunity – where it sweats and there is less hair and therefore where flies feed. Derek doesn’t believe it is the biting fly that transmits it – but a surface feeding fly which feeds on a sarcoid and then transfers the sarcoid element into the site of skin trauma on another horse – which could include where a biting fly had caused tissue damage.
(10:12) Sue says this would fit with periocular sarcoids as flies tend to feed there and Derek again agrees, saying wherever sarcoids occur rarely, they are always associated with wounds which further demonstrates this. Derek uses the analogy of surface feeding flies being like teenagers going to MacDonalds, where the food is greasy, warm and available at almost no cost – whereas biting flies are like Richard Branson who wouldn’t dream of going to MacDonalds but a 5 star Michelin star restaurant – before then saying sometimes the biting flies go there after and have a pub drink and transfer the sarcoid. This all fits the epidemiology of the disease – but the process of exactly how this happens and the link to bovine papilloma virus is not yet fully understood.
(12:36) John summarises the conversation so far and Derek goes on to show how in 1985 in a survey 2.5% of British horses had sarcoids, with an average of 2.5 sarcoids each. In 2018 this had risen to 8% of British horses with an average of 24 sarcoids each - so this disease is steadily increasing.
Chapter 2: Sarcoidy
(15:06) John asks if there are any breeds, ages or predispositions which are more susceptible and Derek says that whilst some studies have demonstrated this he does not think it is so simple having seen sarcoids in just about every breed that is available – he says there are genes which impart susceptibility as there have been outbreaks within families of horses. So it is very difficult to isolate. He also studied age of onset within a study of close to 30,000 horses and the numbers merely mimicked the population – so no definitive evidence, and he has seen 40 year old and 17 day old horses with sarcoids. He is more convinced of conditional, situation and environmental factors over any of age, breed, gender and colour.
(19:05) Sue asks about sarcoids themselves – what do they look like? Derek says it is often misdiagnosed as something else because of how multiformal it is. Because it is a tumour of fibroblasts and not epithelial cells often what you see bears no relation to what you would perceive as a fibroblastic tumour. This is because of the effect of the viral component on the disease and the impact this has on the surround tissues. So firstly the occult form of sarcoid is not the occult tumour – but may contain the tumour – and this must be kept in mind. He goes on to say the circular nature of this form is in effect a result of the mediators diffusing out from the centre. Then the centre
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