Introduction

Feline upper respiratory tract infection (URI) or feline respiratory disease complex refers to contagious acute respiratory/ocular disease that can be caused by multiple organisms. It is most commonly a problem in multicat environments such as shelters, catteries or other large colonies, boarding facilities, and cat shows where significant stress, overcrowding and suboptimal resources may be present. Therefore it is a combination not just of pathogens, but also host and environmental factors that determine the incidence and severity of disease.¹

Clinical Signs

Clinical signs of URI are non-specific and range in severity from mild to severe; typically more severe in young kittens and animals with coinfection and other concurrent disease. Common clinical manifestations are fever, lethargy, inappetence, sneezing, nasal discharge, conjunctivitis and ocular discharge, ulceration of tongue, gums, lips, nasal planum and rarely skin, salivation and coughing. Some clinical signs are more likely to occur with certain pathogens; i.e., oral ulceration with feline calicivirus (FCV), keratitis, dendritic corneal ulcers, skin lesions with feline herpesvirus (FHV), conjunctivitis only with Chlamydophila felis, and coughing with Bordetella bronchiseptica.

Etiologic Agents

Feline calicivirus is a top differential diagnosis for cats with clinical evidence of rhinitis, stomatitis, oral ulceration and conjunctivitis. Less commonly, FCV is associated with polyarthritis, lower airway disease in kittens, and virulent systemic disease.¹ Some more virulent variants of FCV are thought to induce systemic vasculitis in cats, and clinical signs can be severe (peripheral edema, necrosis of extremities, dermal ulceration, DIC, death) even in adult cats previously vaccinated with FVRCP vaccines.¹ Cats recovering from acute infection of the more common FCV strains will shed virus for weeks, but may also become chronically shedding carriers. Transmission is via ocular, oral and respiratory secretions from both acutely infected and carrier cats, from both direct contact and contaminated surfaces. The virus is stable in the environment, can persist for a month or longer and is difficult to decontaminate. It is resistant to chlorhexidine, quaternary ammonium and several common disinfectants. Dilute bleach (1:32) is effective.^1-3

Feline herpesvirus-1 is a top differential diagnosis for cats with clinical evidence of conjunctivitis, keratitis, and facial dermatitis. After acute infection which typically last 2–3 weeks, most cats continue to be chronically infected due to latent virus harbored in the trigeminal ganglion, and recrudescence in stressful situations or during immunosuppression can occur. FHV persists in the environment for a much shorter time period than FCV - a few days - and is susceptible to most disinfectants making direct contact with affected cats the main route of transmission.^1,4

Chlamydophila felis is a top differential diagnosis for cats with clinical signs consisting mainly of conjunctivitis and mild respiratory signs. Typically, younger cats are affected (<1 year) and it appears more prevalent in purebreeds. Ocular effects can include hyperemic edematous conjunctiva, blepharospasm and pain. Corneal ulcers are uncommon. Transmission is mainly through ocular secretions, so close contact with affected cats is required. Shedding from ocular membranes has been demonstrated for up to 60 days, with some cats being persistently infected.⁵ C. felis does not survive in the environment outside of the host.

Mycoplasma spp. are normal commensal organisms of the mucous membranes of multiple species including cats. Mycoplasma felis has been associated primarily with conjunctivitis but is suspected as a primary cause of rhinitis in cats as well. There are multiple Mycoplasma spp. of cats and the pathogenic potential for most is unknown.¹

Many cats have antibodies against B. bronchiseptica, the organism can be cultured from clinically normal cats, and there are sporadic reports of severe lower respiratory disease caused by bordetellosis in kittens and cats in crowded environments or other stressful situations.⁶ B. bronchiseptica is shed through nasal and oral secretions and transmission is through direct contact. The organism is susceptible to common disinfectants.

Diagnosis

Diagnosis of a specific causal agent in feline URI is difficult and may only be useful in large-scale management situations as opposed to individual patients.¹ Because of widespread exposure and vaccination, the positive predictive value (PPV) of serological tests for FCV and FHV is poor and these are not recommended. Several different types of PCR assays are now available. However, these assays also amplify vaccine strains of FCV and FHV. A positive result can occur in normal carrier cats as well as clinically ill cats. As many healthy cats will be positive, the PPV of serologic test results, culture, and PCR assay are low in cats. It is important to remember that positive tests do not prove causation and negative test results do not rule out the pathogens' involvement in the disease.¹

Treatment

Therapy for viral pathogens mainly consists of supportive care including IV or SQ fluids, nebulization, antibiotics for concurrent bacterial infections, appetite stimulants, analgesia for oral ulcers, etc. Feline interferon omega inhibits FCV replication in vitro, but results of controlled studies evaluating efficacy in clinically affected cats with respiratory disease are not available. Currently available anti-viral medications are only efficacious for DNA viral infections such as FHV-1 and not RNA viruses like FCV as they interfere with viral DNA synthesis and subsequent viral replication.³ Famciclovir is safe and effective and is now being used for both acute and long-term therapy for cats with FHV-1 infections at a dose of 90 mg/kg q8 h for 21 days.³ Recently, cidofovir (topically twice daily) was used in a small experimental FHV-1 conjunctivitis study and shown to lessen clinical signs and FHV-1 shedding. Lysine at 250–500 mg orally twice daily may be helpful in some cats with acute or chronic rhinosinusitis from FHV-1 infection (not FCV). However, in a controlled study of shelter cats fed a lysine-fortified diet, a significant positive effect was not noted. Intranasal administration of modified live, intranasal FHV-1 and FCV vaccines may lessen disease in some chronically infected cats, but controlled data are lacking.

If primary bacterial infections are suspected, doxycycline 10 mg/kg, PO, once daily for cats with rhinitis with or without conjunctivitis, is usually effective. Doxycycline is the treatment of choice for B. bronchiseptica, Mycoplasma spp. and C. felis infections,^5,6 and in the last has been shown to be superior to topical administration of tetracycline. Amoxicillin-clavulanate is a good choice in young animals and is effective for most organisms with the exception of Mycoplasma spp. because these organisms lack a cell wall. Doxycycline has been associated with esophagitis and esophageal strictures in cats. It is recommended to never administering dry pills or capsules to cats. Cats with acute disease only need to be treated for 7 to 10 days, except in the case of Chlamydophila felis, where it has been shown that 28 days of therapy are needed to eliminate infection.⁵

Prevention

Vaccination has the ability to significantly reduce clinical signs associated with feline respiratory pathogens, and likely the possibility of transmission, but cannot completely prevent infection. Vaccine protocols should be developed with the individual lifestyle of the cat in mind. Recommendations for vaccine protocols are available through both the American Association of Feline Practitioners and the European Advisory Board on Cat Diseases.

When feline patients with URI are seen in the clinic setting, they should be taken directly to an examination room to not expose other areas of the hospital. If possible, supportive care in the home environment is preferred over hospitalization to reduce stress and transmission. Appropriate disinfection of contaminated areas is necessary before use by other feline patients. When new cats are introduced to a household, 2 weeks quarantine is recommended to prevent spread of stress-induced URI outbreak. Current household cats should be up to date on FHV and FCV vaccine before introducing a new cat.¹

Stress reduction is an important part of management of URI as clinical signs are often worse in cats experiencing social or environmental stress. Shelter cats are particularly at risk and providing noise and visual barriers, hiding places, environmental enrichment, and adequate resources can help mitigate these circumstances.^1,7

References

1.  Cohn LA. Feline respiratory disease complex. Vet Clin North Am Small Anim Pract. 2011;41:1273–1289.

2.  Radford AD, Addie D, Belak S, et al. Feline calicivirus infection. ABCD guidelines on prevention and management. J Feline Med Surg. 2009;11:556–564.

3.  Horzinek MC, Addie D, Belak S, et al. ABCD: update of the 2009 guidelines on prevention and management of feline infectious diseases. J Feline Med Surg. 2013;15:530–539.

4.  Thiry E, Addie D, Belak S, et al. Feline herpesvirus infection. ABCD guidelines on prevention and management. J Feline Med Surg. 2009;11:547–555.

5.  Gruffydd-Jones T, Addie D, Belak S, et al. Chlamydophila felis infection. ABCD guidelines on prevention and management. J Feline Med Surg. 2009;11:605–609.

6.  Egberink H, Addie D, Belak S, et al. Bordetella bronchiseptica infection in cats. ABCD guidelines on prevention and management. J Feline Med Surg. 2009;11:610–614.

7.  Mostl K, Egberink H, Addie D, et al. Prevention of infectious diseases in cat shelters: ABCD guidelines. J Feline Med Surg. 2013;15:546–554.