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CWD Sample Submission for IHC Testing

The United States Department of Agriculture (USDA) has recently made changes in the procedures required for sample collection from cervids for chronic wasting disease (CWD) testing by immunohistochemistry. Ohio is considered free of CWD and has robust surveillance programs in captive and free-ranging deer. The Ohio ADD has tested over 8000 samples per year, for the last several years. The following changes are now required for veterinarians submitting samples to an approved laboratory for CWD testing, including submission of both fresh and formalin-fixed samples.

General ADDL Laboratory Submission and Shipping Guidelines

NOTE: If the animal is a trophy animal, submit the official ID and attach a new official ID to another piece of skin. If no official ID is present, the collector must affix one and record the information. Microchips must be in tissue.

Call the ADDL with any questions or concerns at 614-728-6220.

Article written by Dr. Jeff Hayes, DVM, MS, ADDL Pathology Section Head

Formalin-fixed tissue

(10:1 ratio of formalin to tissue sample)


After removing the brainstem from the foramen magnum, ensure the proper obex sample (bifurcation or “V”) is preserved. Further trim the brainstem section by making a transverse cut ¾ inch in front of the “V” shape bifurcation and an equal distance behind the bifurcation. Place the trimmed obex into the formalin jar.

Medial Retropharyngeal Lymph Nodes (MRPLNs)

Remove each left and right MRPLN as done previously, now, longitudinally incise each lymph node. Place half of the left and half of the right node into the formalin jar, and the other halves into a whirl-pak bag (see below).

Fresh tissue

(collect samples in one labeled whirl-pak bag)


Place the rostral and distal pieces of brainstem in the labeled bag.

Retropharyngeal Lymph Nodes

Place the other halves of each node into the same bag.

ID Tags And Skin

Remove the official ID with a 1”X1” piece of ear attached for each animal sampled, place it in the labeled bag and submit with other fresh tissues. DO NOT PLACE IN FORMALIN.