Coronitis is defined as an inflammation of the coronary band. This condition can be chronic or acute; the chronic condition is usually caused by an autoimmune disease known as 'pemphigus', where the body rejects its own tissues, targeting the skin and mucous membranes. The acute form of coronitis is due to either injury or bruising to the coronary band and underlying tissue, and is usually self-inflicted by the horse when shod. When the band is struck by the shoe on the opposite hoof, this is known as 'tread', and is commonly seen in horses worked in a two-horse team, as they can be injured either by their own shoes, or by their hitch mate's. The coronitis condition known as 'overreach' is caused by the hoof on the same side striking the fore heel. Overreach tends to happen at the gallop or when a horse is a fast trotter or when a horse has a lot of action in their hind end.
Symptoms and Treatment
Sometimes the horse doesn't have an open wound at the coronary band, but swelling is visible, either on only one side or extending throughout the entire coronary band. The area will be hot and tender, and the horse will be lame, sometimes only setting their toe on the ground. In cases caused by injury, the hoof should be washed with warm water with soap, then rinsed in cold water, then soaked in an antiseptic bath. Overreach boots can be used to prevent future injury. In certain cases, coronitis could be caused by an infection, which will result in the swollen, sore skin becoming first gray, then black, and often oozing pus and accompanied by a fever. In cases of severe infection, the skin will die and slough off, leaving an open wound. In cases where the skin sloughs off, symptoms will typically go away once the dead tissue is gone. In cases of coronitis caused by pemphigus, horn production is altered and hoof quality declines. The hoof will lose its shine and will become flaky. The legs may also become swollen and hot to the touch, resulting is stiff, painful movement, The horse will be lethargic and depressed with appetite loss leading to weight loss. Treatment for this type of coronitis is typically immune-suppressing drugs (often required in risky, high doses) and non-steroidal drugs (such as a 'gold salts injection'. Horses that are diagnosed at a young age usually have a better chance of successful treatment than older horses.
Reeks, H. Caulton. Diseases of the Horse's Foot. London: Baillière, Tindall and Cox, 1906. Front Range Frenzy. 2008. Web. 12 Nov. 2011. <http://www.frontrangefrenzy.com/hoofdiseases/>.*
Knottenbelt, Derek, BVM&S, DVM&S, FACVSc. "Pemphigus: The Body Under Attack." Hoofcare & Lameness 77: 17-21. Hoofcare & Lameness. Hoofcare Publishing. Web. 12 Nov. 2011. <http://www.hoofcare.com/>.
*Although this source is more than a century old, the information is still accurate and relevant today.