Cartoon of sick cat

Diagnosis of feline viral rhinotracheitis relies a great deal on presenting clinical symptoms.  Typically illness associated with feline herpesvirus, which causes rhinotracheitis, has more severe upper respiratory tract and conjunctival or ocular signs than other disease-causing agents in cats.  If, however, a specific diagnosis must be determined, there are laboratory tests available to confirm suspicions.  One way to do this would be to isolate the virus itself.  This is done by taking a swab from the sick cat's oropharynx.  This sample is then grown on a special medium and then coloured with immunofluorescence in order to detect feline herpesvirus.  A more sensitive method of detecting this virus is PCR (polymerase chain reaction), where a small piece of virus is amplified and identified.  Unfortunately, getting a positive result for feline herpesvirus does not always mean that that virus is currently causing the clincal symptoms.

Caution must be practiced in interpreting herpesvirus test results.  This is due to the fact that a positive result means that the cat has the virus, but it does not specify whether this caused the rhinotracheitis, as some cats can be subclinical carriers.  A subclinical carrier would have the virus and can potentially spread the virus to other cats, but does not show signs themselves.  If both the PCR and virus isolation come back positive and the cat has been through a recent period of stress, it is more probable that their rhinotracheitis stems from a current feline herpesvirus infection.