Background: Dirty skin with mud packed on may precipitate the condition, but it usually occurs in horses with mild to moderate immune system compromise that sensitizes their skin to wet conditions.
Symptoms: Thick, circular skin lesions appear with a thick and crusty scab and a bit of pus under the scab. Generally appears in damp weather or after the skin is rained on. Worse after a drought when the rain is very acidic and unclean.
Diagnostics: Characteristic lesions; may be identified from skin scrapings or by skin culture.
Special Notes: The causative organism is ubiquitous in the soil, but only some horses acquire the condition. Horses with strong immune systems are fairly resistant, while immune-compromised horses will have recurrent cases. Often self-limiting, but many horses have severe, chronic cases.
Principles for Supplementation: Support the immune system so that healing of the skin can take place.