What samples are needed for rabies testing?

Rabies testing should be performed in accordance with the established national standardized protocol for rabies testing by a qualified laboratory that has been designated by the local or state health department. Euthanasia should be accomplished in such a way as to maintain the integrity of the brain so that the laboratory can recognize the anatomical parts.

Except in the case of very small animals, such as bats, only the head or brain (including brain stem) should be submitted to the laboratory. Fresh frozen (unfixed) tissues are preferred for rabies diagnosis. Refrigerated samples are not preferred and should be used only as a last resort when shipping on dry ice is not possible.

Chemical fixation of tissues should be avoided to prevent substantial testing delays and because it might preclude reliable testing. Questions regarding testing of fixed tissues should be directed to the local rabies laboratory or public health department.

For detailed information about how to submit specimens, see Rabies Specimen Submission Guidelines.

What tests are performed to diagnose rabies?

The direct fluorescent antibody test (dFA) is the test most frequently used to diagnose rabies. This test requires brain tissue from animals suspected of being rabid and can only be performed post-mortem. This test has been thoroughly evaluated for more than 40 years and is recognized as the most rapid and reliable of all the tests available for routine use. All rabies laboratories in the United States perform this test on animals suspected of having rabies. Other tests for diagnosis and research such as electron microscopy (EM), histologic examination, immunohistochemistry (IHC), RT-PCR, and isolation in cell culture are useful tools for studying the virus structure, histopathology, molecular typing, and virulence of rabies viruses.

For a complete list of rabies diagnostic tests performed at CDC and information about how to submit specimens, see Rabies Specimen Submission Guidelines.