Possible Clues:

• Disease of horses
• Taking small space off Sassenachs is a problem for horses
• Rare contagious disease that mainly affects horses
• With horses in one's charge one must worry to have about fifty geese
• In slang, red turns up to make those sick
• Disease acquired from soil in part of southwest France
• Water fowl round lake showing disease
• Waterfowl catching onset of Lyme disease