510 ILCS 65/5
In the event an Illinois owner voluntarily elects to have his equidae tested and a reactor is found, the reactor shall be (a) quarantined until death or until released by a written notice from the Department and (b) permanently identified with a freezemarking brand which shall be applied by an employee of the Department, a veterinarian in the employ of the Illinois Racing Board, or an employee of the Animal and Plant Health Inspection Service of the United States Department of Agriculture or any successor agency. The freezemarking brand shall be not less than 2 inches in height, shall be applied to the left side of the neck of the reactor, and the identifying mark shall be "33" followed by the letter "A" and a number designated by the Department to indicate individual identification.
Any animal under 12 months of age which reacts positively to an official test for EIA shall be quarantined and retested at 12 months of age. If positive at that time, it shall be subject to permanent identification as a reactor and continue under quarantine. Foals being nursed by reactor dams shall be quarantined until they are weaned from their dams and have a negative official test for EIA not less than 60 days following their weaning.
510 ILCS 65/5