An abscess in an infection & inflammation within the horny foot that can cause acute lameness due to the pressure build up from the formation of puss with or without gas pockets.
There are 2 types of abscess.
Sub Solar Abscess -
A sub solar abscess in an infection between the horny sole and sensitive sole
Laminal Abscess (Sub Mural) -
A laminal Abscess is an infection between the horny wall and the sensitive lamina (dermal laminae)
The Horny Sole
The Horny Wall
Common Cause of Abscesses are
Solar penetrations by foreign object
There will be a variable degree of lameness depending on the size of the abscess and the amount of pressure being places on the sensitive structures caused by the underlying infection, this can be a mild lameness to a no weight bearing limb.
There will be heat within the foot and swelling around the coronary bend and fetlock due to the infection, a strong digital pulse can also be felt over the Medial/Lateral digital arteries. In the later stages of infection there will be a pungent smell from the foot and the possibility of sinus tracts on the sole or horny wall.
With Sub Mural abscesses the infection can track up the horny wall and erupt out of the coronary band causing a interruption in the hoof wall production and will travel distally as a horizontal crack.
The Diagnosis of an abscess is first done by examining the foot for penetrations and light pairing of the sole, most of the time there can be obvious sinus tracts that will shoe as a black puss coming out of the sole. If an abscess is present the a pungent smell can also be smelt when examining the foot.
light palpitation of the foot by hand looking for a pain response, and the careful use of hoof testers is also a good way of finding the exact area of infection. light exploration can be carried out and if a high pressure tract is relived the puss will spurt out and an immediate relief can be seen by the horse.
if the abscess is from a nail prick then the use of hoof testers on each clench will show signs of a pain response on the offending nail, when the nail is removed then a black smelly puss can be seen on the nail shank.
if the horse is acutely lame but no abscess can be found after light pairing of the sole then the use of a poultice to soften the feet and dray the infection out can help speed up diagnosis
Once an abscess is located then it can be drained by the use of a hoof knife, (searcher knives are useful as they allow for very accurate work ) this will relive the pressure build up within the foot and allow for the abscessation area to be cleaned.
The use of Hydrogen Peroxide can be advantageous due to the foaming action and the high oxygen content. then the tract can be cleaned with a dilute povidone solution or soluble metronidazole,
Hot tubing of the foot twice a day with a saturated solution of salt or Epsom salts can be beneficial for horses with multiple tracts of infection. then use of a hot poultice for 12-24h after will ensure all the infection is removed, a dry poultice can then be used to allow the foot to harden and also protect the area from re-infection
When the tract has stopped draining then a well fitted wide webbed shoe that has been seated out will allow for good support of the foot and protect the remaining horny foot, the use of pads can be useful in some cases to protect the sole from re infection. however there is still a risk of re infection from contaminates becoming trapped between the healing sole and the pad. The ricsk of re infection can be reduced by using a solar packing material.
A vet will be able to administer Non-Steroidal Anti-Inflammatory drugs that will help reduce the amount of inflammation and help reduce excessive loading on the other limb. antibiotics are not normal given for an abscess that is not draining as this can extend the time it takes for the infection to erupt , but if it is thort that the infection is close to the distal phalanx then they can be used to protect then underlying structures.
An excellent prognosis can be given in the majority of cases and the horse can return to steadily be normal work. But horses with poor foot quality can be prone to reassurance.