After exposure, incubation lasts from two to five days. Sneezing is usually the first and sometimes the only sign observed. Other signs include congestion, eye and nasal discharge and fever. Bacterial pneumonia, a serious complication most frequently seen in young kittens, often develops.
Despite having very similar signs of infection, feline herpesvirus-1, feline calicivirus and feline chlamydia have some signs that are specific. Being familiar with these signs may help with diagnosis. Feline Herpesvirus-1 infection is likely to cause corneal ulcers.
Feline Calicivirus infection is likely to cause mouth ulcers.
Feline Chlamydia infection is likely to cause mild upper respiratory signs, primarily significant eye discharge and conjunctivitis.
However, eye ulcers, mouth ulcers or profuse eye discharge do not always occur. Consequently, the exact cause of the upper respiratory infection may never be identified.
Your veterinarian may wish to perform some diagnostic tests to determine the overall health of your cat as well as the response to the treatment. Some of these may include:
Complete blood count (CBC) to evaluate red blood cells, platelets and white blood cells. This can help your veterinarian determine how the body is responding to the infection.
A blood chemistry profile and urinalysis to evaluate the overall health of the cat.
Feline leukemia and feline immunodeficiency virus testing to rule out leukemia and AIDS. These viruses can weaken the immune system and make your cat more susceptible to upper respiratory infections.
Chest radiographs (x-rays) may be recommended if pneumonia is suspected.