Feline Upper Respiratory Infections

Feline Upper Respiratory

In most cases of feline upper respiratory infections, the use of antimicrobials is not indicated. Most upper respiratory tract infections are due to viral infections, often uncomplicated by secondary bacterial infections. The International Society of Companion Animal Infectious Diseases (ISCAID) guidelines suggests a ten-day monitoring period prior to considering antibiotic treatment; antibiotics may be warranted earlier if the patient’s clinical condition is getting worse.

In some cases, feline upper respiratory tract infections are caused by a primary bacterial infection. In these cases antibiotic therapy is needed. ISCAID guidelines are useful in determining when to provide antibiotics and which to choose.

International Society for Companion Animal Infectious Diseases (ISCAID) Guidelines For Feline Upper Respiratory Infections

Learning Objectives

  • Be aware of the guidelines for feline upper respiratory infections set by the ISCAID.

  • Name the underlying causes of feline upper respiratory infections.

  • Determine the appropriate diagnostic tests and interpretations for cases of feline upper respiratory infection.

  • Explain when the use of antibiotics is appropriate for cases of feline upper respiratory infections and which two antibiotics would be appropriate to use empirically.

  • Identify three alternative treatment options for antibiotics in cases of feline upper respiratory infection and describe when these treatment options are appropriate.

Common Causes of Feline Upper Respiratory Tract Infections 

Feline herpesvirus

Feline viral rhinotracheitis, caused by feline herpesvirus (FHV), is an upper respiratory tract infection that can be associated with secondary bacterial infections. After FHV infection, most cats become lifelong carriers of the virus. Stress or corticosteroid treatment may cause virus reactivation and shedding in oronasal and conjunctival secretions. Infection with FHV requires direct contact with other infected cats and cats who are shedding the FHV virus. Shedding may last for three weeks from oral, nasal, and conjunctival secretions.

Clinical signs of FHV include acute rhinitis and conjunctivitis, and usually pyrexia, depression, and anorexia. Some affected cats may also develop ulcerative, dendritic keratitis.

To establish a diagnosis of FHV, samples of conjunctival, corneal, or oropharyngeal swabs are needed for PCR (polymerase chain reaction) tests. Corneal scrapings or biopsies can also be used. It is not recommended that cats who have been recently vaccinated with a modified-live virus vaccine be sampled because of the likelihood of isolating the vaccine strain.

For treatment of FHV, nursing and supportive care are necessary. Anorexic cats should be fed a diet that is highly palatable, soft, and warm. Mucolytic drugs, such as bromhexine, or nebulization with saline may offer additional relief. Systemic antiviral drugs may be used for the treatment of severe infections, and topical antivirals may be needed in cases of acute FHV ocular disease. Broad-spectrum antibiotics should only be administered with FHV cases that develop secondary bacterial infections which last more than ten days or get worse after five to seven days or if fever and anorexia are present concurrently with mucopurulent nasal discharge.

For prevention, regular vaccination is recommended. For shelters or catteries, annual revaccination is recommended.

Feline calicivirus

Feline calicivirus (FCV) is a highly variable virus, meaning there are many strains that can either be benign or highly virulent. Infection with FCV occurs mainly through direct contact of sick, acutely infected, or virus carrying cats who shed FCV in their oronasal and conjunctival secretions.

Common clinical signs of FCV include oral ulcers, upper respiratory signs, and fever. Cats with "virulent systemic FCV disease" may show clinical signs of pyrexia, cutaneous edema, ulcerative lesions on the head and limbs, or jaundice. FCV may be isolated from nearly all cats with chronic stomatitis or gingivitis. The mortality rate is high in virulent systemic FCV disease-infected cats, especially in adult cats.

Virus isolation and reverse-transcriptase PCR are used to diagnose FCV from conjunctival and oral swabs, blood, skin scrapings, and lung tissue samples. The diagnosis of virulent systemic FCV disease requires virus isolation in the presence of corresponding clinical signs.

Treatment for FCV involves supportive care therapy, including fluid therapy. Anorexic cats should be fed a diet that is highly palatable, soft, and warm. Mucolytic drugs, such as bromhexine, or nebulization with saline may offer additional relief. Broad-spectrum antibiotics should only be administered with FCV cases that develop secondary bacterial infections as per FHV above.

For prevention, vaccination is recommended. Annual vaccine boosters are recommended for cats in higher-risk situations, such as shelters or catteries.

Bordetella bronchiseptica

Bordetella bronchiseptica is a Gram-negative bacterium that colonizes the respiratory tract of felines and is considered to be a primary pathogen of domestic cats. The bacterium is shed in oral and nasal secretions of infected cats. It can establish chronic infections once it colonizes the ciliated epithelium of the respiratory tract.

B. bronchiseptica is associated with a wide range of respiratory signs from fever, coughing, sneezing, ocular discharge, and lymphadenopathy to severe pneumonia with dyspnea, cyanosis, and death.

Bacterial culture and PCR lack sensitivity in confirming B. bronchiseptica infections. Samples for isolation can be obtained from swabs of the oropharynx or via transtracheal wash and bronchoalveolar lavage.

Because B. bronchiseptica may progress to the lower respiratory tract, antimicrobial therapy is necessary even when clinical signs are mild. The use of antimicrobial sensitivity testing is recommended to provide guidance for appropriate antibiotic therapy. When antimicrobial sensitivity data is unavailable, the use of tetracyclines are recommended. Doxycycline is the preferred antimicrobial. Cats with severe B. bronchiseptica infection require additional supportive care and nursing care. 

A vaccine against B. bronchiseptica is available for cats, but is considered a noncore vaccine. In other words, routine vaccination is not recommended for all cats because B. bronchiseptica generally causes mild disease. Rather, only cats specifically at risk of infection should receive the vaccine, such as those in shelters, catteries, other high-density populations, or populations that have a history of confirmed disease.

Chlamydophila felis

Chlamydophila felis is a Gram-negative bacterium that primarily colonizes the conjunctiva. Disease transmission requires close contact between cats, especially through ocular secretions, as the bacterium does not survive well outside the host. Most cases are frequently associated with conjunctivitis and occur in cats under one year of age.

Clinical signs of C. felis can include intense conjunctivitis with pain, blepharospasm, and extreme hyperemia of the nictitating membrane. Transient fever, inappetence, and weight loss may occur shortly after infection, although most infected cats remain well overall and continue to eat.

The preferred method for diagnosing C. felis is through PCR of ocular swab samples. In unvaccinated cats, antibody detection can be used to indicate infection.

For treatment of C. felis, tetracyclines are generally the antimicrobial of choice with doxycycline being the preferred option. Vaccination is an option for prevention and should be considered especially in shelter environments or multicat households with a history of confirmed chlamydial disease. When vaccination is not feasible, single housing and routine hygiene measures are needed to avoid cross-infection. Cats living together for longer terms should be regularly vaccinated. In breeding catteries where C. felis infection is endemic, eradication involves treatment of all cats with doxycycline for at least four weeks (Gruffydd-Jones et al., 2009). Once clinical signs have been controlled, the cats should be vaccinated.


Supplemental Information to Video

Physical Exam Findings

* Temperature: 101.2° F

* Pulse: 184 beats per minute

* Respirations: 28 breaths per minute

* Mucous membrane color and capillary refill time (CRT): Pink and <2 seconds

* Body Condition Score (BCS): 5/9

* General appearance: bright, alert, and responsive (BAR)

* Eyes: Mild serous ocular discharge with mild crusting at the medial canthus of both eyes (OU)

* Ears: within normal limits with minimal debris noted

* Lymph Nodes: no peripheral lymphadenopathy noted

* Integumentary: no lesions noted

* Abdominal palpation: nonpainful, no masses or organomegaly noted

* Digestive: smooth intestines palpated normally

* Genitourinary: small bladder, external genitalia within normal limits

* Respiratory: clear lungs in all fields, patient sneezing, bilateral mucopurulent nasal discharge

* Circulatory: no murmur or arrhythmia noted, pulses strong and synchronous

* Nervous: WNL

* Musculoskeletal: Ambulatory and weight-bearing all four limbs

* Pain Score: 0/5


After History

  1. Because you know how important a good history is, you decide to ask Jonathan some more questions. Which questions would you ask?

Answer: Answers here may vary, but should include basic historical questions about the onset and duration of disease, and whether the disease has worsened since it started. Additional questions could include: Is Sienna indoor only or is she an indoor/outdoor cat? Have new animals been introduced into the household, including newly fostered animals, newly adopted animals, or even animals that are being temporarily watched for friends (catsitting)? Are there any other pets at home? If so, what kind and how many? Has Sienna boarded at a clinic or cattery, or visited a groomer recently? Are there any new environmental changes in the house (this may include respiratory irritants or other stressors)? Is there any recent history of travel with Sienna? If so, when and where, and were there other animals present? Have you given Sienna any medications or treatments since the signs first started? Has she had a history of a similar condition before? When did she last receive vaccines? Which ones?

After Physical Exam

  1. Your physical examination has provided clues to Sienna’s problems. Based on your history and clinical exam findings, where would you localize the disease?

Answer: Upper respiratory tract

  1. What should be included on your differential diagnosis list based on where you localized the disease?

Answer: Feline herpesvirus, Feline calicivirus, bacterial infections are less likely

  1. Based on your differential diagnosis, which diagnostic tests should you perform?

Answer: Fluorescein stain to rule out corneal ulcer. Consider FHV or FCV conjunctival or nasal swab for PCR, but clinical significance might be questionable in an isolated case compared to an outbreak in a cattery.

Before Treatment

  1. What treatment options are available for the different types of upper respiratory infections in cats (remember to consider ISCAID guidelines)?

Answer: It is important to remember that the disease is self-limiting in many cats and supportive care should be considered above prescribing antibiotics. If clinical signs persist for longer than ten days or worsen to systemic signs in five to seven days, antibiotics should be considered. Systemic signs include fever, anorexia, profound lethargy, and brown/green/hemorrhagic nasal discharge. White or yellow nasal discharge is consistent with inflammation and is not synonymous with infection.

  1. How would you like to proceed with treatment?

Answer: Steam therapy, highly palatable or aromatic food, maintenance of hydration, appetite stimulants if needed.


  1. Egberink, H., Addie, D., Belák, S., Boucraut-Baralon, C., Frymus, T., Gruffydd-Jones, T., . . . Horzinek, M. C. (2009). Bordetella Bronchiseptica Infection in Cats: ABCD Guidelines on Prevention and Management. Journal of Feline Medicine and Surgery,11(7), 610-614. doi:10.1016/j.jfms.2009.05.010

  2. Gaskell, R. M., Dawson, S., & Radford, A. (2006). Feline Respiratory Disease. In C. E. Greene (Author), Infectious Diseases of the Dog and Cat(Third ed., pp. 145-158). MO: Saunders.

  3. Gruffydd-Jones, T., Addie, D., Belák, S., Boucraut-Baralon, C., Egberink, H., Frymus, T., . . . Horzinek, M. C. (2009). Chlamydophila Felis Infection: ABCD Guidelines on Prevention and Management. Journal of Feline Medicine and Surgery,11(7), 605-609. doi:10.1016/j.jfms.2009.05.009

  4. ISCAID. (n.d.). Retrieved from https://iscaid.org/

  5. Lappin, M., Blondeau, J., Boothe, D., Breitschwerdt, E., Guardabassi, L., Lloyd, D., . . . Weese, J. (2017). Antimicrobial use Guidelines for Treatment of Respiratory Tract Disease in Dogs and Cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases. Journal of Veterinary Internal Medicine,31(2), 279-294. doi:10.1111/jvim.14627

  6. Richards, J. R., Elston, T. H., Ford, R. B., Gaskell, R. M., Hartmann, K., Hurley, K. F., . . . Sparkes, A. H. (2006). The 2006 American Association of Feline Practitioners Feline Vaccine Advisory Panel Report. Journal of the American Veterinary Medical Association,229(9), 1405-1441. doi:10.2460/javma.229.9.1405