Pathology and Diagnosis

Agency: Natural Resources


There is no gross pathology evident in animals which have died of rabies. Microscopic lesions of the central nervous system are inflammatory and similar to those seen in other virus infections. Negri bodies (inclusion bodies in the cytoplasm of neurons of infected animals) are positive proof of rabies infection.


Rabies is most frequently diagnosed using the direct fluorescent antibody test (dFA) by testing brain tissue from animals that are suspected to have rabies. Since brain tissue is required, the test can only be performed after the animal is dead. Even though there are other testing techniques available for diagnosis, dFA is currently recognized as the most rapid and reliable of all the tests for routine use in detecting rabies in animals. 

For rabies diagnosis in humans there are several tests available that can be performed before death, however no single test is sufficient. Tests can be run on saliva, serum, spinal fluid and skin biopsies of the hair follicles at the back of the neck. 

In Michigan, animal rabies testing is performed by the Michigan Department of Community Health's Bureau of Laboratories Lansing location.


This page is maintained by the Michigan Department of Natural Resources.