To test nonhuman primates for tuberculosis, tuberculin is injected intradermally in which part of the body?

• A. The inside of the front limb
• B. The back of the ear
• C. On the back of the neck
• D. The upper eyelid

Answer: (D)

Delays-type hypersensitivity to tuberculin is measured by the skin reaction at the injection site, so choosing a site that is easy to read, stable, and unlikely to be disturbed is essential. In nonhuman primates, the upper eyelid is used for intradermal tuberculin because the eyelid skin is thin and highly visible, allowing a clear induration to be observed without the animal interfering with the site through grooming or movement. This location also minimizes tissue depth issues that could affect reading a reaction and reduces handling difficulty during the read.

Other sites tend to be less practical for reliable reading in primates: areas with more hair or thicker skin can mask subtle swelling, and locations harder to observe regularly (like the back of the neck or inside a limb) make timely interpretation more difficult. The eyelid provides a consistent, accessible spot to evaluate the reaction in this species.