Cat Flu

Also known as: Feline Upper Respiratory Disease Complex

Introduction

Several pathogens are associated with the development of upper respiratory tract infections ('cat flu') in cats.

The agents usually involved are:

Feline Herpesvirus 1

Feline Calicivirus

Chlamydophila felis

Bordetella bronchiseptica

Other bacteria and viruses act as secondary invaders eg. Mycoplasmas, Pasteurella multocida, Staphylococcus spp., Reovirus

The condition is more likely to occur in groups of cats and therefore individuals in boarding catteries, breeding colonies and rehoming centres are more likely to be affected.

Outbreaks are still common despite widespread vaccination.

Clinical Signs

Clinical signs vary in severity and type according to the infective organism, the level of exposure to the organism, and the immune status of the affected individuals.

It is not always possible to distinguish between the different diseases according to the clinical picture as pyrexia, depression, sneezing and ocular and nasal discharge are common with all agents.

Specific clinical signs associated with organisms include:

Feline Herpesvirus 1 causes a more severe disease

Feline Calicivirus causes oral ulceration

Chlamydophila felis causes chronic conjunctivitis and mild upper respiratory tract signs

Diagnosis

It is usually not necessary to distinguish and isolate specific organisms, especially where individuals in a restricted household are affected.

When an outbreak in a cattery or a colony occurs, a definitive diagnosis may be required to institute specific control measures.

The following tests can be used to isolate the organism responsible:

Viral isolation: oral or conjunctival swabs to detect Feline Herpesvirus and Feline Calicivirus

PCR: conjunctival swab to detect Chlamydophila felis

Culture: oral or nasal swabs to detect Bordetella bronchiseptica

Serology is not useful due to the widespread practice of vaccination. The majority of cats will have positive antibody titres to the causal organisms.

It may be worth assessing for the presence of concurrent chronic viral infections with FIV or FeLV as these may precipitate or exacerbate clinical signs.

Treatment

Nursing care should be done at home if possible. Or if cases have to be hospitalised, barrier nursing should be instituted to avoid spread of infection from one individual to another. Affected cats should not share airspace with healthy cats.

Treatment of clinical cases is mainly supportive and symptomatic:

Antibiotics should be given to control secondary bacterial infections: broad spectrum initially or depending on culture and sensitivity if a poor response is seen.

Aggressive supportive care:

Assist the cat's respiration: providing an oxygen-enriched atmosphere, clear secretions from the external nares, nebulise saline to assist clearance of secretions from the airways, provide decongestants.

Provide fluid therapy: intravenously to provide maintenance requirements if the patient is too debilitated to drink.

Provide nutritional support as cats are often inappetant. They can be enticed with warm and smelly foods, given appetite stimulants such as cyproheptadine or diazepam. An oesophagostomy tube may have to be considered in severely debilitated cats.

Antiviral agents are controversial, but may be useful in cases of Feline Herpesvirus infection, where iododeoxyuridine can be used topically in cases of keratitis/corneal ulceration. Femciclovir may also be beneficial in cases of herpesvirus infection. Oral or topical interferon therapy is still a controversial treatment.

Control

This is especially important in multicat households and catteries.

1. Reduce overcrowding
2. Maintain cat populations as closed as possible: keep cats in separate, stable groups, reduce the number of young cats, separate the groups with adequate partitions
3. Maintain good hygiene: thorough and regular cleaning and disinfection
4. Reduce stress
5. Elimination of breeding queens associated with cat flu
6. Use of an isolation unit: with separate equipment
7. Use of a kittening room
8. Vaccination: vaccination is strongly advised against Feline Herpesvirus 1 and Feline Calicivirus to reduce infectious disease. Queens should receive a booster before mating to maximise maternally-derived antibody. Vaccines are also available against Chlamydophila felis and Bordetella.

Problems with vaccines: No vaccine offers 100% protection, and vaccination does not always prevent infection. Not all strains of Feline Calicivirus are covered by the most commonly used strains of vaccine, which means that cats can develop the disease despite having been vaccinated. Cats may also develop infection with agents against which they are not vaccinated, eg. Chlamydia and Bordetella.

The cat may have been exposed to an overwhelming challenge, or may be immunosuppressed due to another disease such as FIV or FeLV.

The carrier state which can occur may mean that a cat is vaccinated after having been infected, and clinical signs may recur.

Cat Flu Learning Resources
Flashcards Test your knowledge using flashcard type questions	Feline Medicine Q&A 10

References

Harvey, A. (2011) Feline Infectious Diseases Feline Medicine Elective, RVC student notes

Boswood, A. (2009) Outbreaks of Respiratory Disease in cats RVC student notes

Gaskell, R. (1999) Infectious diseases of the cat Saunders