Cat Upper Respiratory Infection: Symptoms and Treatment

1 Common Pathogens

The usual pathogens include viruses (feline herpesvirus, calicivirus), bacteria (Pseudomonas, Staphylococcus aureus, Chlamydia), and fungi (Cryptococcus).

Herpesvirus, calicivirus, and Chlamydia are the most common, though Chlamydia mainly affects the eyes.

Feline herpesvirus infects only cats and multiplies in the conjunctiva and respiratory epithelium, and can also replicate inside nerve cells, leading to a lifelong latent infection. It spreads by contact, and kittens develop severe signs.

Calicivirus is common but rarely fatal, multiplying within the cell cytoplasm.

Chlamydia is a Gram-negative organism that causes conjunctivitis and can also produce upper respiratory signs; it is most common in cats from five weeks to nine months old and may cause pneumonia.

Cryptococcus is a fungus with a strong affinity for the upper airways that can also affect the nervous system and skin, causing a systemic fungal disease.

2 Recognizing the Symptoms

Viral infection: early signs are lethargy and reduced appetite, more frequent sneezing, and watery eye and nasal discharge. Some cats develop fever, mouth ulcers, and drooling, followed by conjunctivitis with mucopurulent eye discharge, and in serious cases coughing and breathing difficulty. Immune reactions can also cause keratitis, corneal ulcers, and uveitis; herpesvirus tends to cause worse eye and respiratory signs than calicivirus, whose hallmark is tongue ulcers.

Bacterial infection: Chlamydia produces obvious eye signs, including red swollen conjunctiva and membranes sticking together from fibrin, plus mild rhinitis and sneezing.

Fungal infection: Cryptococcus causes chronic cough, nasal congestion, gray mucopurulent nasal discharge (sometimes with blood), and over time swelling of the nasal bridge and facial distortion.

3 Ruling Out Other Causes

Because eye and nasal discharge and sneezing are common to many conditions, veterinarians also rule out: inhaled allergies such as pollen; oral disease, marked by facial swelling, tartar, periodontal disease, loose teeth, and drooling; tumors, especially in older cats (adenocarcinoma, lymphoma); and nasal foreign bodies such as litter or plant material.

4 Treatment and Prevention

Provide sensible supportive care: ensure adequate fluids and nutrition, and gently clean the eyes and nose.

For herpesvirus, supplement lysine. Antiviral proteins and feline interferon may be used at 300,000 to 500,000 IU/kg.

Bacterial cases are treated with antibiotics such as amoxicillin-clavulanate, doxycycline, or azithromycin.

Eye drops manage ocular signs, and cats with mouth ulcers benefit from an oral rinse or dental gel to keep the mouth clean.