Final answer:
The SICCT test for tuberculosis in cattle involves injections of avian and bovine tuberculin into the skin of the neck and measures any change in skin thickness to detect a delayed-type hypersensitivity reaction indicative of TB exposure.
Step-by-step explanation:
The Single Intradermal Comparative Cervical Tuberculin (SICCT) test is used to detect tuberculosis (TB) in cattle. For the SICCT test, two injections are made into the skin of the neck: one with avian tuberculin and the other with bovine tuberculin. The injection sites are located on either side of the midline of the neck, slightly apart from each other.
The skin is measured before and after injection, and the test result is based on the difference in skin thickness at the two sites 72 hours after the injections. This test is a type of delayed-type hypersensitivity reaction, where a positive response usually indicates exposure to the TB pathogen.