At some time in their life, most cats are exposed to pathogens that can cause respiratory disease. Most feline respiratory infections cause only mild disease, but some can lead to serious health problems. Our Just Cats Clinic team explains what you need to know about respiratory infections that affect cats.

Feline herpes virus in cats

Feline herpes virus type 1 (i.e., feline viral rhinotracheitis) is the most prevalent feline respiratory infection cause, with up to 97% of cats exposed to the pathogen, and 80% of exposed cats infected lifelong. Forty-five percent of lifelong affected cats shed the virus periodically, most commonly when they are stressed. Other important information about feline herpes virus includes:

  • Clinical signs — Feline herpes virus signs include clear or colored ocular or nasal discharge, coughing, sneezing, conjunctivitis, and fever.
  • Diagnosis — Feline herpes virus is typically suspected when young or unvaccinated cats exhibit indicative signs. For a definitive diagnosis, polymerase chain reaction (PCR) testing can identify the viral DNA.
  • Treatment — Supportive care, including maintaining hydration and adequate nutrition, is necessary when treating feline herpes virus. Other treatments may include nasal decongestants, antibiotics to manage secondary infections, and antiviral drugs to treat corneal lesions.
  • Prognosis — Infected cats can have recurring episodes, especially when stressed. Most bouts are mild and self-limiting, but some cats, especially those with co-existing health conditions, can become severely ill.
  • Prevention — Feline herpes virus vaccines are recommended for all cats. The vaccines are not 100% effective but can reduce disease severity.

Feline calicivirus

Feline calicivirus is the second-most common pathogen that causes respiratory disease in cats. The infection is especially common in shelters and breeding catteries where cats are housed in crowded conditions. Other important information about feline calicivirus includes:

  • Clinical signs — Feline calicivirus most commonly causes nasal and ocular discharge, sneezing, coughing, and conjunctivitis. The illness can also lead to oral ulcers, and the infection can spread to the lungs and cause viral pneumonia, which leads to difficulty breathing.
  • Diagnosis — Feline calicivirus is typically suspected based on history and clinical signs, but PCR testing can confirm the diagnosis, if necessary.
  • Treatment — Treatment is similar to feline herpesvirus, but other measures may be needed to address painful oral ulcers, including pain medications, a feeding tube, and a rigorous dental cleaning.
  • Prognosis — Prognosis depends on disease severity, but most cats recover in days or weeks.
  • Prevention — Feline calicivirus vaccines are recommended for all cats. The vaccines are not 100% effective but can reduce disease severity.

Feline chlamydiosis

Chlamydia felis is a bacterial infection that is transmitted through eye secretions in cats who have close contact. Other important information about feline chlamydiosis includes:

  • Clinical signs — Feline chlamydiosis causes conjunctivitis. Initially, the cat’s eye discharge is clear and later turns mucoid and yellowish.
  • Diagnosis — PCR testing can identify C. felis DNA.
  • Treatment — Treatment typically involves systemic antibiotic treatment, and topical eye treatments may also be necessary.
  • Prognosis — When appropriately diagnosed and treated, most cats affected by feline chlamydiosis have a good prognosis.
  • Prevention — Vaccination is recommended for cats housed in multi-cat housing facilities. The vaccine does not prevent infection but can minimize disease signs.

Feline bordetella

Bordetella bronchiseptica is a bacterial infection that commonly affects cats housed in high-density populations, such as breeding catteries and shelters. Infection is transmitted through oral and nasal secretions, and bacteria can spread to cats from infected dogs. Other important information about B. bronchiseptica includes:

  • Clinical signs — Signs can range from mild, such as coughing, sneezing, and ocular discharge, to life-threatening, such as difficulty breathing, blue-tinged mucous membranes, and sudden death. Serious disease is most common in young cats who develop lower respiratory tract infections.
  • Diagnosis — Diagnosis can be made by culturing B. bronchiseptica or PCR testing.
  • Treatment — Treatment involves antibiotic therapy and supportive care, such as nutritional support and fluid therapy.
  • Prognosis — Most cats affected by uncomplicated B. bronchiseptica infections recover within 10 days of starting antibiotic treatment. 
  • Prevention — Vaccination is recommended for cats housed in multi-cat housing facilities. 

Feline fungal infections

Numerous fungal species, including Crypotococcus neoformans, Aspergillus fumigatus, Histoplasma capsulatum, and Blastomyces dermatiditis, can cause respiratory infections in cats. The most common, C. neoformans, is transmitted when a cat inhales the fungal spore. Bird droppings and decaying plant matter are potential infection sources. The infection can spread to other body parts, including the central nervous system. Other important information about C. neoformans includes:

  • Clinical signs — Infection is most commonly nasal, with signs that may include nasal or facial swelling, sneezing, chronic nasal discharge, non-healing wounds around the nose and mouth, polyp-like growths in the nose and throat, vocalization changes, noisy breathing, inappetence, weight loss, and difficulty breathing.
  • Diagnosis — Diagnosis is through cytological examination of nasal discharge. Imaging, such as X-rays, CT scan, or MRI, may also be necessary to determine the depth of fungal invasion into the nasal and sinus bony structures.
  • Treatment — Treatment typically involves prolonged administration of antifungal drugs.
  • Prognosis — Cats who are diagnosed early in the disease course with no central nervous system involvement typically have a favorable prognosis, as long as they receive the recommended treatment.
  • Prevention — Keeping your cat indoors helps reduce their exposure to C. neoformans and other fungi.

Contact our Just Cats Clinic team if your cat is exhibiting respiratory disease signs, so we can identify the causative agent and instigate an appropriate treatment plan.