General guidelines for rabies diagnosis:
http://www.cdc.gov/rabies/diagnosis/index.html
CDC protocol:
http://www.cdc.gov/rabies/docs/RabiesDFASPv2.pdf
OIE protocol:
Section B. Diagnostic Techniques, OIE Terrestrial Manual 2008
http://www.oie.int/eng/normes/mmanual/2008/pdf/2.01.13_RABIES.pdf