510 ILCS 30/5
When one or more animals in a herd have been classified as reactors to an official test, the entire herd, except steers, spayed heifers and calves under 6 months of age, shall be quarantined immediately and the owner so notified . An accredited veterinarian or a veterinarian in the employ of the Animal and Plant Health Inspection Service of the United States Department of Agriculture, or any successor agency, shall permanently hot iron brand each animal classified as a reactor, within 15 days after classification of such animal as a reactor, on the left hip with the letter "B", such letter to be not less than 2 nor more than 3 inches in height, and shall place a special identification tag in the left ear of such reactor. The veterinarian applying an official test for brucellosis shall immediately notify the Department of each such reactor on forms furnished by the Department, giving the number of the tag placed in the left ear and the number of any tag in the right ear. Reactors shall be shipped for slaughter within 30 days of test date, except that the Department may, upon request, grant an extension of not more than 30 days. Suspect animals which have a history of having aborted and are from a herd containing reactors may be designated as reactors by the veterinarian obtaining the blood samples, when approved by the Department. Suspect animals in herds under quarantine due to brucellosis infection may be designated as reactors by the Department if deemed advisable in the interest of brucellosis eradication. No person shall remove any reactor identification tag.
All animals classified as suspects to an official test shall be positively identified and their movement restricted to the premises where found until they are retested and found negative, or identified as reactors.
Animals with a positive result to an official test at livestock auction markets or marketing centers may be slaughtered or returned to the herd of origin only by permit and must remain under quarantine for further evaluation.
510 ILCS 30/5