Hyperkeratosis


Introduction.


The part of the dog’s foot that is normally in contact with the ground is covered with a hard ‘dry’ layer of dead cells.  These cells contain a high level of keratin which is a tough, insoluble protein that is the major constituent of hair, nails, horn and hooves. The function of this keratinised layer of cells is to protect the underlying sensitive ‘living’ tissues of the foot.  Under normal circumstances this surface layer of dead cells is constantly being abraded away as the dog exercises.  However, these abraded tissues are replaced by more keratinised cells produced by the underlying (living) cells, ensuring that the protective layer of ‘dead’ cells is maintained at a more or less constant thickness.


The keratinised layer is relatively inelastic and cracking of the pads is a common occurrence in dogs.  This cracking can be caused by a number of different agents.  In most cases these cracks are confined to the superficial layers of the pads and do not penetrate down into the underlying sensitive layers.  This type of cracking rarely causes any discomfort to the dog unless aggravated by other factors, e.g. excessive exposure to alternate wet and dry conditions, chemicals etc., that modify the extent to which cracking occurs and, hence, the severity of the condition.  These cracks usually heal spontaneously, or with minimum treatment, once the underlying pre-disposing factors have been eliminated.  On the other hand, hyperkeratosis is a specific disease condition.



What is hyperkeratosis?


The term “hyperkeratosis” literally means “above normal levels of keratinised tissue”.  It may be defined as “a disabling but non-life-threatening condition resulting from an abnormally excessive development of the layer of dead keratinized cells which form the outer layer of the pads and the subsequent development of deep cracks, corny accretions etc.



What is the current situation regarding Hyperkeratosis?


The incidence of hyperkeratosis appears to be very low but for various reasons this may not represent the true situation.  The condition may not be recognised as such or owners may elect not to disclose the fact that the condition is present in their stock.



What causes hyperkeratosis?


Hyperkeratosis can be due to a number of causes.  In the past many cases were associated with other disease conditions such as distemper, hard pad, etc., and developed as a consequence of that dog developing the disease. Since this was consequential to a specific, recognised disease it may be regarded as a secondary hyperkeratosis.


However, as Bedlington fanciers we are concerned with a form of the condition that does not seem to be attributable to a specific disease or a specific pre-disposing factor. Hence, this may be considered as a primary hyperkeratosis.



What are the signs of digital hyperkeratosis?


Unless the feet are examined regularly, the first indication will be that the dog shows signs of lameness and may be reluctant to exercise.  The dog will show signs of discomfort or pain even when only light pressure is applied to the pad.


A careful examination of the foot reveals the presence of deep cracks and, possibly, eroded areas.  As the condition develops these cracks penetrate down into the underlying, sensitive layers of the feet.  In extreme (grossly neglected) cases the cracks may even penetrate as far as the bone.  Bleeding may occur on occasions. Deep circular plaques of keratinised tissue (corns) may be present and there may be ridges of hard tissue (feathering), particularly at the edges of the pads.  In some cases corny accretions, sometimes up to 0.5 inches long, may develop at the margins. The extent of the cracking and its severity can vary considerably.



Photograph of a Bedlington foot that is affected with Hyperkeratosis

(reproduced with the permission of Mr Harvey Bell)



Although the age at which the condition is first noticed can vary somewhat, it is frequently noticed initially when the dog is 6-12 months old.  


There does not appear to be any significant difference in the incidence of the condition in relation to the sex of the affected dogs.



Confirmation of the Condition.


Positive diagnosis is possible by means of a histopathologic examination of a tissue samples taken from the affected pad(s).



Can hyperkeratosis be treated?


Digital hyperkeratosis cannot be cured.  Any form of treatment is directed towards alleviating discomfort/pain.


The initial stages of the treatment involve softening the keratinised tissues by treating the pads daily for several days using a “hydration” product, as recommended by the veterinary surgeon. Any excessive keratinised tissue that overlaps the edges of the digital pads can then be carefully trimmed away and any corns carefully filed or pared, taking care not to cut into the underlying sensitive tissues.  


Ointments containing antibiotics and/or corticosteroids may be required for treatment of cracked, eroded or ulcerated pads and the feet are often bandaged for short periods of time to protect them and to give them a chance to heal.  


Use of an antibiotic to minimise the possibility of a secondary bacterial infection may also be indicated.



Is it possible to prevent a dog developing digital hyperkeratosis?


Although many breeders in the immediate post-war years considered hyperkeratosis to be an inherited condition and took steps to try to eliminate it, seemingly with considerable success, the possibility that it could be a genetic disorder was never investigated despite the fact that there was considerable evidence, albeit largely anecdotal, that seemed to support that view.


Consequently, the only way forward at that time was to assume that the condition was inherited and to use only known healthy stock for breeding or, if buying a puppy, to buy only from a reputable breeder.  


This was the situation until relatively recently.


In August 2008 Professor Lieb and a team of geneticists at the University of Berne, in conjunction with ANTAGENE, started a research project to analyse the genomes of a number of breeds of dog (including the Irish terrier, but not the Bedlington terrier) in which footpad hyperkeratosis was a problem.  The end result of the research was that there was a common gene mutation that was responsible for footpad hyperkeratosis in all the breeds involved in the research project.  This allowed the development of a single test to cover all the breeds covered by the research.


The test was made available in England via Animal DNA Diagnostics at Cambridge.  Although Bedlington terriers had not been involved in the research project it was felt that the fact that the causal gene mutation was common to all the breeds that were checked suggested that the test could be applicable to Bedlingtons.  The initial response from Animal DNA Diagnostics was that they would “review the situation”.  They have subsequently informed the Breed Clubs that the test is available to Bedlington terrier owners.  


For more information re this test:


Telephone: 01223 395577


Email: info@animaldnadiagnostic.co.uk


Web Page: www.animaldnadiagnostics.co.uk



Hence, by testing all breeding stock and adopting a breeding regime that does not result in affected puppies being born, it would be possible over time to eliminate the condition.




Note.


Ken Bounden’s book, “The Bedlington Terrier”, contains a chapter on “Hyperkeratosis”. This provides a comprehensive and very readable account of hyperkeratosis and includes a concise account of “history” of the condition.





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