Definition

A common viral respiratory disease of domestic and exotic cats characterized by upper respiratory signs, oral ulceration, pneumonia, and occasionally arthritis, or a highly fatal systemic hemorrhagic disease.

Pathophysiology

Rapid cytolysis of infected cells with resulting tissue pathology and clinical disease.

Systems Affected

• Gastrointestinal-ulceration of the tongue common; occasional ulceration of the hard palate and lips; infection occurs in intestines; usually no clinical disease.
• Hemic/Lymphatic/Immune-hemorrhage.
• Musculoskeletal-acute arthritis.
• Ophthalmic-acute serous conjunctivitis without keratitis or corneal ulcers.
• Respiratory-rhinitis; interstitial pneumonia; ulceration of the tip of the nose.

Genetics

None

Incidence/Prevalence

• Persistent infection common.
• Clinical disease-common in multicat facilities, shelters, and breeding catteries.
• Routine vaccination-reduced incidence of clinical disease; has not decreased the prevalence of the virus.

Geographic Distribution

Worldwide

Signalment

Signs

Causes

• A small, non-enveloped single-stranded RNA virus, feline calicivirus.
• Numerous strains exist in nature, with varying degrees of antigenic cross-reactivity.
• More than 1 serotype.
• Relatively stable and resistant to many disinfectants.

Risk Factors

• Lack of vaccination or improper vaccination
• Multi-cat facilities
• Concurrent infections with other pathogens (e.g., FHV-1 or FPV)
• Poor ventilation

Differential Diagnosis

• Feline viral rhinotracheitis
• Chlamydiosis
• Bordetella bronchiseptica

CBC/Biochemistry/Urinalysis

No characteristic or consistent findings

Other Laboratory Tests

Serologic testing on paired serum samples-detect a rise in neutralizing antibody titers against the virus.

Imaging

Radiographs of the lungs-a consolidation of lung tissue in cats with pneumonia.

Diagnostic Procedures

• Cell cultures to isolate the virus-oral pharynx; lung tissue; feces; blood; secretions from the nose and conjunctiva.
• PCR.
• Immunofluorescent assays of lung tissue-viral antigen.

Pathologic Findings

• Gross-upper respiratory infection; ocular and nasal discharge; pneumonia with consolidation of large portions of individual lung lobes; possible ulcerations on the tongue, lips, and hard palate; systemic hemorrhages.
• Histopathologic-interstitial pneumonia of large portions of individual lung lobes; ulcerations on epithelium of the tongue, lips, and hard palate; mild inflammatory reactions in the nose and conjunctiva; systemic hemorrhages.

Appropriate Health Care

Outpatient, unless severe pneumonia or hemorrhages occur

Nursing Care

• Clean eyes and nose as indicated
• Provide soft foods
• Oxygen-with severe pneumonia

Activity

Patients should be restricted from contact with other cats to prevent transmission of the causative virus.

Diet

• No restrictions.
• Special diets-perhaps to entice anorectic cats to resume eating.
• Soft foods-if ulcerations restrict eating.

Client Education

Discuss the need for proper vaccination and the need to modify the vaccination protocol in breeding catteries to include kittens before they become infected (often at 6–8 weeks of age) from a carrier queen.

Surgical Considerations

None

Drug(s) Of Choice

• No specific antiviral drugs that are effective.
• Broad-spectrum antibiotics-usually indicated (e.g., amoxicillin at 22 mg/kg PO q12h).
• Secondary bacterial infections of affected cats are not nearly as important as with FHV-1 infections.
• Antibiotic eye ointments-to reduce secondary bacterial infections of the conjunctiva.
• Appropriate pain medication-for transient arthritis pain.

Contraindications

None

Precautions

None

Possible Interactions

None

Alternative Drug(s)

None

Patient Monitoring

• Monitor for sudden development of dyspnea associated with pneumonia.
• No specific laboratory tests.

Prevention/Avoidance

• All cats should be vaccinated at the same time they are vaccinated against FHV-1 and FPV; routine vaccination with either MLV or inactivated vaccines should be done as early as 6 weeks of age and repeated every 3–4 weeks until at least 16 weeks of age.
• Breeding catteries-respiratory disease is a problem; vaccinate kittens at an earlier age, either with an additional vaccination at 4–5 weeks of age or with an intranasal vaccine at 10–14 days of age; follow-up vaccinations every 3–4 weeks until 16 weeks of age.
• American Association of Feline Practitioners-classifies FHV, FPV, and calicivirus as core vaccines; vaccinate all cats with these three agents on the initial visit as early as 6 weeks of age, repeat every 3–4 weeks until 16 weeks of age, and 1 year after the last kitten vaccine; revaccinate for calicivirus every 3 years.
• Vaccination will not prevent virus infection in a subsequent exposure but will prevent serious clinical disease caused by most strains.

Possible Complications

• Interstitial pneumonia-most serious complication; can be life-threatening.
• Secondary bacterial infections of the lungs or upper airways.
• Oral ulcers and the acute arthritis usually heal without complications.
• Systemic hemorrhagic disease may be severe and fatal.

Expected Course and Prognosis

• Clinical disease-usually appears 3–4 days after exposure.
• Once neutralizing antibodies appear, about 7 days after exposure, recovery is usually rapid.
• Prognosis excellent, unless severe pneumonia or systemic hemorrhagic disease develops.
• Recovered cats-persistently infected for long periods; will continuously shed small quantities of virus in oral secretions.

Associated Conditions

Affected cats may also be concurrently infected with FHV-1, especially in multi-cat and breeding facilities.

Age-Related Factors

Usually occurs in young kittens whose maternally derived immunity has waned.

Zoonotic Potential

None

Pregnancy/Fertility/Breeding

Generally no problem, because most cats have been exposed or vaccinated before becoming pregnant.

Synonyms

Feline picornavirus infection-FCV originally classified as a picornavirus; older literature refers to the infection by this name; no known picornavirus that infects cats.

See Also

Chlamydiosis-Cats

Abbreviations

• FCV = feline calicivirus
• FHV = feline herpesvirus
• FPV = feline parvovirus
• MLV = modified live virus
• PCR = polymerase chain reaction

Client Education Handout Available Online