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White Line Disease: Progression and Identification

White Line Disease: Progression and Identification

White line disease  describes the result of an establishment of hoof eating micro-organisms within  the  hoof wall, usually concurrent with another hoof defect, imbalance or injury where the microbes gain entry. WLD feeds on the intertubular horn which fill the tiny voids between the strands of horn tubules. Affected areas begin as areas of wall/sole seperation. Untreated, these voids fill with the digested hoof material, manure and other debris combine creating ideal conditions for the proliferation of the microbes and more hoof loss

White Line
Seedy toe or WLD associated with laminitis. The damaged wall is removed and the remaining horn disinfected. This foot will need shoeing. Note the new, tighter growth emerging.

This article attempts help horse caretakers understand and identify white line disease in horses.

Tubular and Intertubular Horn

The hoof wall is composed of countless whisker-like horn tubules. These horn tubules are constantly produced at the coronary band by the horn papillae. Horn tubules provide  structure, shape and resistance to vertical compression of the horse above. Intertubular horn is  also constantly emerging from the coronary band, but from in the spaces between the horn papillae. Intertubular horn fills the gaps between all of the individual strands of horn providing cohesive stability, resistance to wear, and mass to the hoof wall. Both components are made the same keratinized horn material, but this matrix gives the hoof great strength while remaining flexible.

How White Line Disease Affects the Hoof

Many horses have a small degree of WLD , especially horses in wet environments. Any defect to the hoof wall not open to air flow such as nail holes or old abscess tracts will be prone to WLD invasion.

how to treat hoof abscess
minor case of White Line Disease, this one may be from a resolved submural abscess

Grass Cracks

Grass cracks, named for the dewy fields that can lead to chronically overly wet hooves,  describe numerous, small, superficial splits  caused by the erosion of the binding intertubular horn beneath the surface of the wall from white line disease.  Like grass, they start from the bottom and progress upwards.  The loss of intertubular horn is what causes this delamination of the hoof wall and the weakened areas to fray and split.

Grass Cracks. photo: tribeequus.com.
Delamination appears as loose, shelly wall is caused by WLD
Delamination,  breakdown of the hoof wall in layers, appears as loose, shelly wall.

Premature Loose Shoes and Clinches Due to WLD

Horseshoe nails, especially loose or ill-fitting can exacerbate WLD. When the wall looses it’s intertubular horn, it loses stability. The damaged wall near the shoe is the most damaged and will not resist vertical compression.  Instead of growing down, it  will flare out to the side. This causes the clinches to loosen. Loose nails move with each step, enlarging the nail holes,  leaving even more weakened hoof for WLD to homestead. Clipped shoes that are not hot fit will also cause this sort of damage because WLD will invade the tiny crack between hoof wall and clip.

WLD worsened by ill fitting clip, long toe and loose nails. photo: atlantaequine.com
loose clinches, overgrowth, bad clip fit=WLD photo: stabletostable.com

Toe Cracks

A toe crack will originate from the center of the toe where the WLD first gains entry. The weakness can be from an old abscess, laminitis, clubby foot, excessive length of toe or from an inherent weakness in some hooves associated  with the mid-dorsal notch of the coffin bone.

The mid dorsal notch of the coffin bone may be a weak spot in the hoof wall. Photo: equinepodiatry.com
entrance for WLD in toe
entrance for WLD in toe
Same foot, from above
Same foot, from above

If the hoof is not returned to a state of balance and the WLD isn’t addressed with methods I will cover a future article, the crack will get larger.

White Line Disease
Toe crack combined with hoof imbalance creates a larger void leading to more WLD

And larger.

White Line Disease
Toe cracks due to excessive toe length and white line disease

Until you have a full thickness crack extending upwards into the coronary band and inwards towards the laminae. This shearing will cause lameness and even rotation of the coffin bone similar to laminitis.

White line disease originally caused by abscess. Neglect has caused a laminitis-like version of white line disease.
White line disease originally caused by abscess. Neglect has caused a laminitis-like version of white line disease. The crack is shearing the sensitive structures and causing inflammation and pain.

Conclusion

White line disease is a very common condition in horses, especially those that already have compromised hooves. Horses with WLD are easy to spot due to the predictable progression of these hoof-hungry microbes.  Fortunately, most cases can be improved with best farrier practices, more frequent trimming/shoeing and environmental changes. I hope to share my thoughts and methods for the management of white line disease  in an upcoming article, so please like, subscribe for updates.

UPDATE-Check out my article Hoof Cracks: 3 reasons why you have them and how to get rid of them  for my methods of managing WLD.

 

 

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Hoof abscesses: symptoms and causes

Most Hoof abscesses are pretty simple to treat at home, I recommend this method after consulting with your veterinarian. Other than losing training time and a small fortune in elasticon, your horse will recover, the damaged hoof will grow out, and only the memory will remain.

Unless it doesn’t. This article , although absolutely no substitute for veterinary consultation, will go over the causes of your garden variety, inconvenient “gravel” abscess, as well why some horses seem to always be either having or recovering from abscess related lameness.

horse hoof abscess
Fix my paw!

 

Symptoms of a hoof abscess

  • the horse may go from normal or slightly off to a grade 3-5 lameness rapidly and unexpectedly in one limb. An affected forelimb will be more obvious.
  • the horse may aggressively manipulate it’s stance and gait to avoid weight-bearing on affected foot.  This horse is so lame, your significant other could diagnose.
  • Swelling or sensitivity of the coronary band, pastern or fetlock.
  • a bounding digital pulse can be felt on one or both branches of the arteries that run down each side of the back of the pastern of the lame leg  (medial versus lateral pulse can help pinpoint location of the infection).
    location for observing digital pulse

    Not always true, but abscesses often occur after paying nonrefundable horse show fees but prior to events such as a motivated buyer coming to see your prospect, trail ride vacation, graded stakes races etc..

Causes of abscesses

“An accumulation of purulent exudate. In the foot, this usually refers to a localised accumulation of exudate between the germinal and keratinised layers of the epithelium, most commonly subsolar or submural.”

Equine Veterinary Education, Vol. 19, June 2007

The above excerpt is a great definition of a hoof abscess, more simply, an abscess is (usually) a pus trapped between the insensitive and sensitive tissues.

The author then goes on to divide the abscess by it’s location: either between the sensitive and insensitive sole (subsolar) on the underside of the foot or trapped behind the hoof wall (submural) .

the “gravel” abscess

This is, by far, is the most common cause of abscessing in my experience, especially if the horse is barefoot.

The “gravel” type of abscess is caused by a small piece of debris getting jammed into a weakened spot in the white line or seat of corn area of the hoof.palmar-foot-drawing-labeled

Click to enlarge or check out structures of the hoof post.

Horses affected with white line disease , a common, fungal invasion of the insensitive horn.  are even more prone to the gravel type of abscess.

If debris manages to penetrate beyond the protective and insensitive hoof wall, bacterial invasion  into the  soft, sensitive tissue (corium) inside the hoof will follow.

Once the body barrier of hoof is penetrated, the abscessing process begins. The horse’s immune systems goes on the offence to prevent further damage from the foreign body: inflammation sets in, a thin, new layer of horn is produced to wall off the debris. White blood cells flock to the site. to fight off the bacteria. Enzymes released by this liquefies the now necrotic tissues involves, which produces the dark grey exudate associated with this condition.This  pocket of serum trapped against a minimally elastic hoof wall and the sensitive tissues within the hoof capsule. This combination is very painful for the horse.

Bad or close nails

Bad/ “Hot” nails

A misplaced nail can be the cause of an abscess. The nail is driven inside the white line and penetrates the soft tissue within the hoof capsule. You will know this because the horse reacts suddenly. He may not set his foot down, instead shaking it inches above the ground. Blood will seep from the clinch or nail head.

Hopefully farriers will circumvent the abscess cycle at this point. They will remove the nail, pour some antiseptic into the offending  and resulting hole, and most will inform the owner so they will be especially observant of that foot.and ensure the horse is up to date on his tetanus vaccination.

By removing the offending object and disinfecting, it is likely that the horse will suffer no more from this incident.

Close nails

A close nail is a nail that is driven into insensitive horn, but displaces hoof material in a way that affects the functioning of the hoof. There is no blood as the sensitive tissue hasn’t been breached. The horse may react to the nail being driven, but not the “kicked in the gut” reaction of the bad nail.

The close nail impedes the function and circulation of the adjacent sensitive foot. This may not become obvious for up to two weeks after the nail was driven. At this point the abscess will run its course as described for the gravel.

It is a good idea to remove the shoe and treat the hoof to speed  recovery and ease pain.

Horses with thin walls, previous hoof damage, clubby or low heels , and wry hoof are more likely to have close nails than a strong footed individual.

hoof abscess
Upright “wry” type of hoof. This hoof is badly twisted due to extreme varus or toed-in conformation in his pastern joint.

Horses that do not stand patiently are also more likely to have a close nail as the farrier cannot distinguish the horse dancing around the aisleway from pain or lack of manners.

Driving nails into a horse’s foot takes years and years to become skilled at. There is a very small area where nails can safely be places and no two feet are quite the same. The last thing a good shoer wants to do is hurt your animal, but it will happen occasionally.

not much room for error. photo: healthyhooves.ca

A good shoer will take responsibility and be glad that this injury is fairly easy to treat.

Abscessing from the inside

Horses with diseases or injuries to the hoof sometimes suffer from abscessing without any external cause.  Horses that do not receive regular hoof care and horses with known hoof problems will  often suffer from chronic abscessing because there is a ongoing internal abnormality.

This is not meant to be a thorough guide to all hoof infections and horses with problems like these should be seen by an equine veterinarian for best results.

Chronic laminitis and pedal osteitis

Horses with a history of laminitis/founder are an excellent example of abscessing due to septic pedal osteitis (coffin bone infection).  The coffin bone of the laminitic horse gets progressively more damaged with each episode. These abscess can be submural or subsolar depending on which portion of the bone is affected.

coffin bone normal and one with changes due to pedal osteitis photo :eponashoe.com

Seedy Toe

Seedy toe
chronic laminitis and a nasty fungal invasion causes a condition commonly called Seedy Toe. This foot requires a high level of management between farrier, owner and vet.

Horses with chronic laminitis are also likely to have chronic submural abscessing in the toe. This is a result of malformed, scarred and or damaged horn that is a result of  laminitic cycle is prone infection.

Trauma

The coffin bone may fracture. A fragment of bone that is broken away is called a sequester. The sequester can result septic pedal osteitis, lameness and abscessing. The offending segment may require veterinary intervention to end chronic abscessing.

Horses with coffin bones that have be damaged from trauma can abscess if the injury leads to infection.

Horses with thin soles and/or  worked on hard surfaces can also  develop pedal osteitis. Horses with coffin bones weakened by any disease  are also predisposed to  this internal abscessing.

Acute Laminitis

Horses in the acute stage of laminitis can suffer from abscessing from the extreme internal injuries taking place within the hoof capsule.

Acute laminitis with subsolar abscess caused by pressure from rotated coffin bone
Acute laminitis with subsolar abscess caused by pressure from rotated coffin bone

If a horse presents this type of abscess you are in need of qualified professionals with experience dealing with laminitis.

If a “professional” attempts to pare away at the solar surface of this horse to “dig out” the “infection” please reconsider this person’s expertise in dealing with hooves in general. This practice generally not recommended. The soft tissue will almost always prolapse through the sole causing further insult to an already bad situation.

Again, under no circumstances should an opening be created in the adjacent sole. This seldom leads to the abscess, generally leads to hemorrhage and may create a persistent, non-healing wound with increased potential for bone infection.”

Dr. Stephen O’Grady “Managing Hoof Abscesses”

Keratoma

A keratoma is tumor made of a horn (hoof material) that develops between the coffin bone and the hoof wall. Keratomas are not common, usually benign and a skilled horse person may be able to identify an affected hoof as the growth causes distortions in the hoof wall and white line.

Removal of a keretoma. Note the distorted coronary band that would alert a wise horse person to the abnormality. Photo: Roodandriddle.com

Occasionally, pressure from the growth can cause  necrosis of the adjacent portions of the coffin bone  leading to Osteomyelitis abscessing. These keratomas may need to be removed under veterinary supervision to end the cycle of chronic osteomyelitic abscessing.

For more on keratoma read Dr. O’Grady’s case study.

Conclusion

A horse with an abscess is a common occurrence if one keeps horses for any length of time.  Luckily, most are treated, recovered from and back to work in under two weeks.

Horses that have chronic abscessing may be helped if the causation of the infection is identified. More aggressive treatment may be necessary for horses with certain types of abscesses.

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Middle Tennessee Farrier
Elizabeth the Farrier