What Is Feline Upper Respiratory Infection?
Feline Upper Respiratory Infection (URI) is one of the most common infectious diseases in cats, often referred to as "cat flu." According to a review in Veterinary Clinics of North America: Small Animal Practice (Cohn, 2011), up to 30–50% of cats in shelters develop upper respiratory infection symptoms.
The most common pathogens include:
| Pathogen | Proportion | Characteristics |
|---|---|---|
| Feline Herpesvirus (FHV-1) | ~50% | Lifelong carrier after infection; can reactivate during stress |
| Feline Calicivirus (FCV) | ~25–40% | Can cause oral ulcers; has multiple serotypes |
| Chlamydia felis (C. felis) | ~10–20% | Primarily causes conjunctivitis |
| Mycoplasma | Secondary infection | Often a complication of other infections |
Symptoms
- Sneezing: The most common and earliest symptom
- Nasal discharge: Ranging from clear and serous to yellow-green and purulent (with secondary bacterial infection)
- Ocular discharge: Conjunctival redness and swelling, tearing, eyelids stuck together
- Nasal congestion: Audible breathing, reduced sense of smell leading to decreased appetite
- Fever: Body temperature exceeding 39.5°C (103.1°F)
- Oral ulcers: Especially common with FCV infection
- Drooling: Caused by oral pain
- Lethargy and decreased appetite
When Should You Visit the Veterinarian?
Seek veterinary care immediately in the following situations:
- Complete refusal to eat for more than 24 hours (cats must not go without food for extended periods)
- Breathing difficulty: Open-mouth breathing, rapid breathing
- White cloudiness or ulceration on the cornea (FHV-1 can cause corneal ulcers)
- Dehydration: Decreased skin elasticity, dry gums
- Kittens or immunocompromised cats showing any symptoms
- Symptoms lasting more than 7–10 days without improvement
Home Care
For mild upper respiratory infections, a veterinarian may recommend primarily supportive home care:
- Keep the environment warm and comfortable: Provide a quiet, warm resting area
- Encourage eating: A cat's reduced sense of smell will significantly decrease appetite. Gently warming wet food (not exceeding 38°C / 100°F) can enhance the food's aroma. Strong-smelling foods (such as fish-flavored canned food) may be more appealing
- Steam therapy: Bring your cat into a bathroom with warm steam for 10–15 minutes to help thin nasal secretions
- Clean eye and nose discharge: Gently wipe with a warm, damp cloth
- Ensure adequate hydration: Provide fresh water and high-moisture wet food
FHV-1 Lifelong Carrier Status and Recurrence
According to a review in Veterinary Microbiology (Gaskell et al., 2007),virtually all cats that have been infected with FHV-1 become lifelong carriers. The virus lies dormant in the trigeminal ganglia and can reactivate during stressful events (moving, surgery, illness, introduction of a new cat), causing symptom recurrence.
For cats with recurring episodes, veterinarians may recommend:
- L-Lysine supplementation: Some studies suggest lysine may help inhibit FHV-1 replication, but a 2015 meta-analysis by Bol & Bunnik questioned its effectiveness; this remains controversial
- Stress reduction: Environmental enrichment, stable daily routines
- Immune support: Maintaining good nutrition and overall health
- Antiviral medication: Severe or recurrent cases may be treated with famciclovir
Prevention
- Vaccination: The FVRCP vaccine (FPV + FHV-1 + FCV) can reduce the severity of illness but cannot completely prevent infection
- Isolate new cats: Newly introduced cats should be isolated for at least 2 weeks
- Environmental disinfection: FHV-1 and FCV are susceptible to common disinfectants
- Reduce stress: Stress is the primary trigger for FHV-1 reactivation
References
- Cohn, L.A. (2011). Feline respiratory disease complex. Veterinary Clinics of North America: Small Animal Practice, 41(6), 1273-1289.
- Gaskell, R.M. et al. (2007). Feline herpesvirus. Veterinary Research, 38(2), 337-354.
- Bol, S. & Bunnik, E.M. (2015). Lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats: A systematic review. BMC Veterinary Research, 11, 284.
- Radford, A.D. et al. (2009). Feline calicivirus infection. ABCD guidelines on prevention and management. Journal of Feline Medicine and Surgery, 11(7), 556-564.