Feline upper respiratory disease and conjunctivitis

(Feline calicivirus, Feline herpesvirus, Feline viral rhinotracheitis, Chlamydophila felis (formerly Chlamydia psittaci), Bordetella bronchiseptica, Avian flu)

Feline calicivirus (FCV), feline herpesvirus (FHV) (rhinotracheitis virus), Chlamydophila felis (formerly Chlamydia psittaci) and Bordetella bronchiseptica (BBb) are just four of the organisms which can cause upper respiratory disease (cat flu) or ocular signs such as conjunctivitis in the cat. There are others, for example at Comparnion Animal Diagnostics, at the University of Glasgow, we have identified cat pox virus in some samples from cats with oral ulceration and have detected Haemophilus felis in mild cases of upper respiratory disease. In addition, non-infectious conditions can masquerade as respiratory infections: most notably feline asthma, nasopharyngeal polyps, foreign body and neoplasia. Cat flu is a misnomer, since it is not caused by a member of the influenza virus family, but is caused by FHV or FCV. Although avian (bird) flu virus (strain H5N1) can infect cats, it is not a major or common infection at this time and its inclusion on this page is more to answer the many questions being asked at present, than because it is a serious threat to cats. It is my view that any threat to either cats or humans from avian flu N5N1 virus is being seriously over-dramatised by the media.

Laboratory testing for respiratory infections is very useful, but is no subsititute for a thorough clinical examination. Persistent conditions may require examination under general anaesthetic, and possibly radiography, biopsy or endoscopy for final diagnosis.

Most of this webpage is written for veterinary surgeons, I apologise to lay persons for usage of terms and words which are unfamiliar, and I hope that you will find the answer to your question in my Frequently asked questions section.

Feline calicivirus

Feline herpesvirus

Chlamydophila felis

Bordetella bronchiseptica

Avian influenza strain H5N1

Controlling respiratory infections in catteries

Frequently asked questions - this part is written for non-veterinarians

Recommended laboratories

Learn more - download an e-book on feline infectious upper respiratory disease and feline chronic lymphocytic plasmacytic gingivostomatitis or attend a masterclass on infectious respiratory disease in August 2006, given by the author of this page, Dr Diane Addie.

Feline calicivirus


Clinical signs




Risk to humans


Feline calicivirus (FCV) and feline herpesvirus (FHV) are the two viruses commonly associated with cat flu. FCV cat flu is usually less severe than that caused by FHV. FCV is frequently found in cats with chronic gingivostomatitis which is dealt with on another webpage.

The genome of FCV is RNA, which is more prone to mutation than DNA. The larger the group of cats, the more variation there is in the virus population found. This can give rise to extremely virulent strains, outbreaks of which have been reported across the USA and recently in the UK.   FCV has also been associated with a limping sydrome, which affects many limbs, causing shifting lameness and which can be a post-vaccinal reaction.

The main method of spread of the cat 'flu viruses is by direct contact of one cat with another. Large amounts of virus are present in saliva, tears and nasal secretions (FCV may also be shed in urine and faeces). Thus it can be spread by cats sniffing each other, mutual grooming and sharing feeding bowls. Sneezed droplets may travel 1-2 metres and cat 'flu can spread rapidly through a cattery unless cats are housed individually with sneeze barriers. Both of the cat 'flu viruses are relatively fragile: FCV lasts about a week outside the cat and FHV lasts a day. Plainly, however, these viruses can be spread within a cattery on cages, food dishes, litter trays, people, etc. so good hygiene precautions should be taken.

Clinical signs

Cat flu

Affected cats or kittens are pyrexic, sneeze and typically have painful ulcers on the tongue, soft and hard palates. FCV cat flu only rarely progresses to pneumonia.

Fading kittens

Feline calicivirus is a cause of fading kittens, even in households of cats which are fully vaccinated against FCV.  The kittens become anorexic and die in the first 1-4 weeks of life.  On post mortem, the thymus is depleted and the lungs are pneumonic.  Histopathology of the lungs is required to differentiate FCV-related pneumonia from FHV-related pneumonia, and/or a sample of lung can be put into viral transport medium for virus isolation or reverse transcriptase-polymerase chain reaction (RT-PCR).  On gross autopsy, inhalation pneumonia is more likely to affect anterior lung lobes, whilst pneumonia of  infectious origin is more likely to affect caudal and anterior lung lobes.

Acute virulent feline calicivirus infection

Across the USA, outbreaks of FCV have been reported in which there was jaundice, oedema, sloughing of the foot pads and up to 40% mortality. Recently, outbreaks have been reported in the UK. The variants which cause this are extremely contagious, in one report, a veterinarian transmitted the infection to her own cat via hairs on her clothing. FCV vaccination does not seem to protect against these strains.


Feline calicivirus is excreted continually from the oropharynx, so samples of saliva can be taken any time, though as early as possible after onset of clinical signs is always advisable. FCV infection is best diagnosed by virus isolation - the veterinary surgeon sends a swab covered in the cat's saliva, in viral transport medium, and the laboratory grows it on cell culture. RT-PCR for detecting viral RNA, is potentially less sensitive because of the high genomic variability of FCV strains, which might cause some strains to be missed. With virus isolation false negative results are rare. Virus isolation also allows detection of feline poxvirus, which occasionally causes oral ulceration indistinguishable clinically from FCV.

On post mortem examination, lung histopathology shows alveolar epithelialisation.

Recommended laboratories.


Treatment is largely symptomatic, with good nursing being extremely important, coaxing the cat or kitten to drink and eat enough to maintain adequate hydration. Severe cases may require feeding by nasogastric or gastric tube. Broad spectrum antibiotics are usually given to combat secondary bacterial infection. Putting the cat into a steamy bathroom and using Vick's vaporub to help keep nasal sinuses clear can be helpful. However, make sure that the cat is away from Vick's around feeding time, since cats need to smell their food in order to eat it - use of more aromatic foods, like sardines, chicken livers, will encourage the cat to eat. Recombinant feline interferon omega (Virbagen Omega®, Virbac, France) at a dose of 1MU/kg s/c daily or every other day can help an acutely ill cat.


  The main method of spread of the cat 'flu viruses is by direct contact of one cat with another. FCV can survive 24-48 hours in the environment, so indirect transmission is possible, as is aerosol transmission. Large amounts of virus are present in saliva, tears and nasal secretions (FCV may also be shed in urine and faeces). Thus FCV can be spread by cats sniffing each other, mutual grooming and sharing feeding bowls. Sneezed droplets may travel 1-2 metres and cat 'flu can spread rapidly through a cattery unless cats are housed individually with sneeze barriers. Both of the cat 'flu viruses are relatively fragile: FCV lasts about a week outside the cat and FHV lasts a day. Plainly, however, these viruses can be spread within a cattery on cages, food dishes, litter trays, people, etc. so good hygiene precautions should be taken. Around a fifth to a quarter of all cats sheds FCV at any one time.

Feline calicivirus vaccination
There are many cat flu vaccines available. Kittens are routinely vaccinated from eight to nine weeks of age, receiving a second dose at 12 weeks old, or 3-4 weeks after the initial injection. Cats should receive a booster at a year of age, and, according to AAFP recommendations, boosters thereafter every 3 years, over the scapula. There are four strains of FCV commonly available in vaccines: F9, 255, G1 and 423. Heska have introduced an intranasal FCV and FHV vaccine called Ultra-Nasal, in the USA. There is concern that vaccination with older strains of vaccinal calicivirus (especially the F9 strain) may not give protection against many field isolates.

Risk to humans

None at time of writing.

UK expert: Dr Alan Radford at the University of Liverpool Veterinary School.

USA expert: Dr Kate Hurley at the University of California, Davis, Veterinary School.


Further reading

Feline Advisory Bureau boarding cattery website

Gaskell RM, Dawson S, Radford A.  Feline respiratory disease.  2006  Infectious Diseases of the Dog and Cat. Third Edition. Editor: Greene, Craig. Saunders Elsevier.  11830 Westline Industrial Drive, St Louis, Missouri 63146.  145-154

Hurley K, Pessavento P, Pedersen NC, Poland A, Foley J. 2004 An outbreak of hemorrhagic calicivirus in cats in southern California, summer 2002. JAVMA 224  241-249

Lauritzen A., Jarrett O., Sabara M. 1997. Serological analysis of feline calicivirus isolates from the United States and United Kingdom. Veterinary Microbiology. 56 55-63

Radford AD, Dawon S, Wharmby C, Ryvar R, Gaskell RM. 2000. Comparison of serological and sequence-based methods for typing feline calicivirus isolates from vaccine failures. Veterinary Record 146 117-123

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Feline herpesvirus


Clinical signs




Risk to other species


Cat 'flu is caused by either feline calicivirus (FCV) or feline herpesvirus (FHV - also known as feline viral rhinotracheitis virus - FVR), or, uncommonly, a combination of both. FHV is a DNA virus. FHV infection is the more serious virus, it may lead to pneumonia and death.

Over 90% of cats have been exposed to FHV and 80% of exposed cats become infected for life, shedding virus intermittently. The virus becomes latent in the trigeminal ganglia, an immune-privileged site, and the virus does not produce many viral proteins, an additional way of hiding from the immune system. Viral shedding occurs about a week following stress, corticosteroid or cyclosporin A treatment, and usually lasts between hours and 1-2 weeks. 

Examples of stress in a cat:

  • being rehomed
  • moving house
  • new additions to house, for example a new baby, dog or cat
  • too many cats in one house (over 6)
  • going into cattery
  • surgery or trauma (e.g. a road accident)
  • intercurrent illness
  • pregnancy, parturition, lactation

Clinical signs

FHV causes more severe cat flu than FCV does. Typical cat flu signs: sneezing, anorexia, depression, oculonasal discharge, pneumonia and even death.  Kittens which survive to 14 days may have swollen eyes, with corneal ulceration or even ruptured eyeballs under their still closed eyelids.  Some kittens who survive feline herpesvirus infection may continue into adulthood with chronic sinusitis or rhinitis.

In very young kittens a few days to weeks old, FHV is a major cause of fading, which is when kittens stop eating, lose weight and die. At post mortem they are found to have pneumonia, thymic atrophy, congested lungs, the body will probably be underweight for the kitten’s age.  Histopathology shows acidophilic intranuclear inclusion bodies. 

Ocular clinical signs of feline herpesvirus infection

The commonest ocular sign of FHV infection is ulceration of the cornea (the front of the eye) and, if left untreated, the eyeball may rupture (see photo). One or both eyes may be distorted by adhesions from the eyeball to the inner eyelid.

This poor little kitten has a burst left eye and an ulcerated right eye due to feline herpesvirus. The left eye had to be removed - fortunately for her, she found a good home with the veterinary surgeon who extirpated the eyeball!



Ocular manifestations of FHV:

  • corneal ulceration
  • symblepharon
  • uveitis
  • eosinophilic keratitis
  • stromal keratitis
  • corneal sequestrum
  • keratoconjunctivitis sicca
  • chronic or recurrent conjunctivitis

Recommended veterinary ophthalmologists with special expertise in cats:

French expert: Prof. Alain Regnier, Ecole Nationale Veterinaire, Toulouse, France.

UK expert: John Mould BA BVSc DVOphthal ILTM MRCVS, Eye Veterinary Clinic, Marlbrook, LEOMINSTER, Herefordshire, HR6 0PH
Tel: 01568 616616
Email: johnmould@eyevetclinic.co.uk

USA expert: Dr David Maggs, University of California, Davis, California, USA.

(Please note that if you wish your cat to be referred to a veterinary specialist you must get your own veterinary surgeon to arrange this for you, Royal College of Veterinary Surgeons rules will not allow specialists to see you without a letter of referral from your own veterinary surgeon.)

Chronic rhinitis

FHV infection should always be suspected in cats with recurrent clinical signs such as conjunctivitis and chronic sinusitis, especially when there is a history of stress a few days prior to onset of clinical signs. Some kittens who have had cat flu may continue into adulthood with sinusitis or rhinitis, their breathing is more audible than that of normal cats, they snore when asleep and may have a permanent or recurrent mucopurulent nasal discharge and sneezing.


Oral or conjunctival swab, corneal scrape or lung from dead kitten submitted for virus isolation or PCR.  If sending lung from a faded kitten, put some into 10% formol saline for histopathological examination and some into viral transport medium. Remember that FHV shedding is intermittent, so while a positive result is definitely positive, a negative result may simply mean that you have missed the shedding time.  Try to time swabbing to be either at the beginning of the animal being symptomatic, or a few days to a week after stress occurring.

Recommended laboratories for FHV testing



Guardians of cats with 'flu should always seek veterinary advice, as many cats will require antibiotics to control secondary bacterial infections. The cat should be tempted to eat with small but frequent portions of aromatic foods such as sardines, roast chicken or liver. In order to clear the nasal passages it is beneficial to the cat if he can be confined to a steamy bathroom for an hour each day. Vick Vaporub can be applied to the chin or a few drops of eucalyptus oil put on the cat's bedding. The cat should be cleaned gently with a cloth and warm water, especially if he can no longer groom himself, and kept warm until dry.

Cats with eye discharges should have their eyes bathed three or four times a day with a warm solution of salt and water, using one teaspoonful of ordinary table salt (sodium chloride) in one pint (half a litre) of water. Veterinary surgeons may prescribe antibiotic eye ointments for cats with secondary bacterial conjunctivitis. Cats with FHV eye ulceration can sometimes be treated under general anaesthetic, the edge of the ulcer is lightly removed with a dry cotton wool bud. However, if the eyeball bursts, the eye may have to be removed.

Human anti-herpesvirus drugs (e.g. Acyclovir - Zovirax) are not particularly effective in feline herpesvirus infection and can be toxic, so are not recommended for use in the cat.

Trifluorothymidine ointment for treatment of ulcers and keratitis requires a special import licence in the UK and can sometimes be obtained from veterinary ophthalmologists. Feline interferon omega (Virbagen Omega,® Virbac) has also been used topically for FHV-associated ocular disease (Jongh, 2004): a 5MU vial is diluted in 9ml of 0.9% NaCl and used as eye drops.  2 drops are instilled in each eye 5 times a day for 10 days.

Cats with chronic rhinitis are notoriously difficult to treat. Many have to take antibiotics continuously or intermittently all of their lives. Some veterinarians offer radical surgery removing the small bones inside the nose, in really severe cases. In the USA, some cats with chronic rhinitis have been successfully treated using the intranasal vaccine. Cats with chronic rhinitis should be tested for FeLV and FIV. If feline herpesvirus is definitely involved, anecdotal reports suggest that it is helpful to use interferon omega (Virbagen Omega, Virbac, 50,000 - 100,000 units orally daily) and the amino acid l- lysine added to the cat's food. L-lysine competes with arginine in the formation of the FHV capsid protein. Vetoquinol have brought out the first veterinary preparation of l-lysine, it is called Enisyl-F. 1ml of Enisyl-F contains 250mg L-lysine.


L-lysine doses:

Adult cats - 250-500mg BID for 6 weeks; if there has been no more than 1 'flare-up' during this 6 week period the cats are switched to 250mg 2 or 3 times weekly.

Kittens - 250mg once or twice daily for 6 weeks; if no more than 1 'flare-up' in the 6 weeks then 250mg 2 or 3 times weekly.


In the UK, if you have difficulty sourcing Enisyl-F, contact Vetoquinol, on 01280-814500



Feline herpesvirus prevention by hygiene

Fortunately FHV survives only a few hours in the environment and is susceptible to most disinfectants.

Clean contaminated food bowls, etc. using bleach diluted 1:32 in water with washing up liquid to disinfect.

Test breeding queens by virus isolation or PCR from an oropharyngeal swab but bear in mind that FHV shedding is intermittent and occurs post-stress.  Use the feature of virus reactivation by stress to advantage: stress carrier queen 2-3 weeks prior to kittening by moving her into her kittening room.  This will cause viral recrudescence before the kittens are born, so shedding will be stopped when they are born.  It will also boost her antibodies, giving the kittens increased maternally derived antibody and a longer period of protection. Use the intranasal vaccine (Ultranasal, Heska) on kittens of known FHV carrier cats from 2-3 weeks of age. (For more on FHV prevention for cat breeders - see my e-books.)

Cats entering a disease-free colony should be quarantined for 3 weeks and virus detection attempted at least twice a week before being allowed to mix with the other cats. 

Feline herpesvirus vaccination

Vaccination against feline herpesvirus is not as complex as FCV vaccination, since there is essentially only one serotype (FHV-2 turned out to be a laboratory contamination!!!) Vaccination ameliorates clinical signs but doesn't prevent infection or development of latency.  Two vaccines are given to kittens, usually from 8 weeks of age onwards (occasionally earlier - see above) and a booster vaccine is given after a year. The American Society of Feline Practitioners (AAFP) recommend boosters thereafter every 3 years, which is different to the data sheets for most vaccines, but which is the regime I endorse.

AAFP vaccine guidelines can be downloaded from their website.

The Advisory Board of Cat Diseases, a European version of the AAFP, will release its guidelines within the coming months.

Vaccination does not prevent induction of a carrier state, so a carrier cat may never have shown clinical signs. 

Risk to other species

FHV is completely different from human and canine herpesvirus infections and there is absolutely no risk to other species from an FHV infected cat. Nor do people with cold sores pose a risk to cats. 

Further reading

Gaskell RM, Dawson S, Radford A. Feline respiratory disease. 2006 Infectious Diseases of the Dog and Cat. Third Edition. Editor: Greene, Craig. Saunders Elsevier. 11830 Westline Industrial Drive, St Louis, Missouri 63146. 145-154

Jongh O.  2004  A cat with herpetic keratitis (primary stage of infection) treated with a feline omega interferon.  Veterinary Interferon Handbook.  Editor Karine de Mari.  Published by Virbac.  138-147

D.J. Maggs 2001 Update on the diagnosis and management of feline herpesvirus-1 infection. Consultations in Feline Internal Medicine 4. Editor John August

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Chlamydophila felis


Clinical signs




Risk to humans and other species


Chlamydophila felis is an obligate intracellular parasite and is the major cause of conjunctivitis (inflammation of the eyelids) in the cat. The incubation period from infection to clinical signs, is up to 14 days. Most infected cats are under 2 years old. Originally the organism was called Chlamydia psittaci var felis, and the condition called feline pneumonitis, but pneumonia is a relatively rare event in the cat.

Clinical signs

The most common clinical sign of Chlamydophila felis infection is conjunctivitis. A peculiarity of this infection is that the conjunctivitis is usually unilateral and it becomes bilateral. The discharge usually begins serous and progresses to mucopurulent. Some kittens have died of C. felis related pneumonia.

Chlamydophila felis has been linked to infertility in the cat, but there is no real evidence that it causes feline infertility (unlike human Chlamydiosis). I have examined various stillborn and aborted kittens and have never been able to detect C. felis (though a negative is more difficult to prove than a positive!).


The best diagnostic technique is polymerase chain reaction (PCR).


The treatment of choice is doxycycline (Ronaxan, Merial Animal Health) at 10mg/kg (i.e. 2 x 20mg tablets for a 4kg cat) s.i.d. for 4 weeks or until 2 weeks after the end of clinical signs. Doxycycline treatment stops shedding 9-25 days after the start of treatment. Chlortetracycline ointment stops shedding 14-25 days after treatment begins.

Doxycycline is contraindicated in pregnant cats as it may affect the unborn kitten, and should not be used in kittens under 6 months because it can cause discolouring of the teeth. An alternative treatment is 1% chlortetracycline ointment (Aureomycin opthalmic ointment, Fort Dodge Animal Health) q.i.d. for 4 weeks or until 2 weeks after the end of clinical signs.

Fucithalmic ointment does not work, neither does Synulox, other penicillins or sulphonamides. Azithromycin resolves clinical signs but fails to clear infection.

Treat all the cats in the household with doxycycline, whether symptomatic or not.


Chlamydophila felis is shed in the ocular secretions (and possibly faeces) for at least 35 days and has been recorded for up to 18 months in experimental infection, although clinical signs last only days to weeks. Transmission is direct, through contact with ocular secretions, and indirect, via fomites. Chlamydophila felis have both intracellular and extracellular forms, infection is via the extracellular elementary bodies which are small (0.3 m) resistant particles with rigid cell walls.

Chlamydophila vaccines are not designated as core vaccines by the American Association of Feline Practitioners. Fel -O -Vax 4, Pentofel, Katavac Eclipse (Fort Dodge Animal Health), are inactivated vaccines. From 8 weeks of age, two doses 3-4 weeks apart, s/c. Annual boosters. Vaccination does not prevent Chlamydophila shedding, indeed may predispose to carrier state, but does ameliorate clinical signs.

Since vaccination does not prevent infection, prevention of infection consists mainly of avoiding exposure of susceptible cats to infection: cat breeders should test their existing cats to establish whether or not they have endemic Chlamydophila and new cats to prevent introducing infection where none previously existed. Obviously, hygiene precautions should be taken when treating infected cats and preventative treatment of asymptomatic cats - hands should be washed between cats and, where eye ointment is used, each cat should have its own tube labelled with its name (put your label directly onto the tube, not the box). Warn cat owners to wash their hands carefully after handling an infected cat and to avoid touching their own eyes after handling the cat.

MDA protects kittens until 7-9 weeks of age, after which kittens should be isolated from infected cats.

Risk to humans and other species

Chlamydophila felis is different from Chlamydophila trachomatis, which is the human form causing conjunctivitis, salpingitis and infertility. Nevertheless, there are documented cases of humans becoming infected by infected cats, so some caution needs to be taken when handling potentially infected cats. Humans are more likely to get psittacosis (fever, lymphadenopathy, pneumonia) from birds than from cats. Cats may also become infected by birds, but the likelihood of infection from a human source is unknown.

Serologic surveys of dogs show evidence of exposure to Chlamydophila, and they have been implicated in chronic superficial keratitis of the dog. The cat is unlikely to become infected by human, ovine or porcine Chlamydophila.

Further reading

Greene C.E. Chlamydial infections. 2006 Infectious Diseases of the Dog and Cat. Third Edition. Editor: Greene, Craig. Saunders Elsevier. 11830 Westline Industrial Drive, St Louis, Missouri 63146. 245-252

M. McDonald, B.J. Willett, O. Jarrett, D.D. Addie. 1998 A comparison of DNA amplification, isolation and serology for the detection of Chlamydia psittaci infection in cats. Veterinary Record. 143 97-101

Owen WMA, Sturgess CP, Harbour DA, Egan K, Gruffydd-Jones TJ. 2003 Efficacy of azithromycin for the treatment of feline chlamydophilosis. JFMS 5 305-311

Sparkes AH, Caney SM, Sturgess CP, Gruffydd-Jones TJ. 1999 The clinical efficacy of topical and systemic therapy for the treatment of feline ocular chlamydiosis. J Feline Med Surg. 1(1):31-5.

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Bordetella bronchiseptica


Clinical signs




Risk to other species


B. bronchiseptica is a pleomorphic, aerobic, gram negative coccobacillus which causes respiratory infection in cats, and death of kittens up to 8 weeks old. B. bronchiseptica has been isolated from 11 percent of 740 cats sampled in the UK. The prevalence was 19.5% in rescue catteries, 9% in breeding catteries and 0% in household pets. Transmission is usually from infected dogs or cats. Infected cats frequently have a history of having been in a rescue or boarding cattery or contact with a dog suffering from kennel cough.

Clinical signs

Harsh, productive or non-productive cough in an otherwise well cat. White froth produced, as in dogs. Signs generally resolve in 10 days.
URT disease: sneezing, ocular discharge, dyspnoea, pyrexia.
Tonsillitis, submandibular lymph nodes raised.

Fatal broncho-pneumonia has been reported in kittens up to 8 wks old.


Oropharyngeal swab, swab of nasal discharge, tracheal wash or sample of pneumonic lung into charcoal Amies bacterial transport medium to a reliable veterinary laboratory. B. bronchiseptica may be difficult to isolate from carrier cats because low numbers of organisms are shed and are easily overgrown by other flora, so selective media such as charcoal-cephalexin agar (Oxoid, Unipath, UK) or Bordet-Gengou agar may be used to suppress undesirable bacterial overgrowth. Characterization of isolates can be performed by ribotype analysis. Blood samples can be taken for antibody detection.


First choice: Doxycycline 20mg (Ronaxan, Merial) 2 tablets sid for 5 days.

Second choice: Trimethoprim-sulfadiazine for 5-7d (i.e. one Tribrissen 20 (Schering-Plough) per day or one Trimacare 20 (Animalcare Ltd) per day). Never divide these tablets as the cats froth at the mouth after dosing and don't use in cats under 1kg.

Note that B. bronchiseptica is NOT susceptible to penicillins.


Vaccinate all cats going into rescue and boarding catteries (and some breeding catteries) with Nobivac Bb (Intervet).  Vaccinate in-contact dogs with Intrac (Schering-Plough) or Nobivac® KC (Intervet). Intrac is not licensed for use in the cat.

The primary route of infection is via oro-pharyngeal and nasal secretions and excretions from infected hosts, so isolate infected animals from uninfected animals and disinfect hands, food bowls, etc.   Minimize overcrowding, stress, intercurrent diseases.  Ensure adequate ventilation.

Post-partum shedding of B. bronchiseptica has been demonstrated in seropositive queens from which no Bordetella could be isolated prior to kittening, suggesting a carrier state. Bacterial shedding has been known to occur for as long as 19 weeks and is not always controlled by antibiotic therapy.

Risk to other species

B. bronchiseptica is primarily an infection of dogs, causing kennel cough. B. bronchiseptica has caused fatal pneumonia in humans with AIDS, however, no contact with either cats or dogs was demonstrated in a series of 9 patients, suggesting that the humans were not infected by pets.

B. bronchiseptica also causes fatal pneumonia of guinea pigs and can cause "snuffles" in rabbits, and it would probably be wise to keep infected cats, dogs or humans away from guinea pigs, rabbits and rats.

Further reading

Nobivac Bb website.

Gaskell RM, Dawson S, Radford A.  Feline respiratory disease.  2006  Infectious Diseases of the Dog and Cat. Third Edition. Editor: Greene, Craig. Saunders Elsevier.  11830 Westline Industrial Drive, St Louis, Missouri 63146.  145-154

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Avian (bird) flu H5N1


Clinical signs




Risk to humans


Avian influenza virus, subgroup H5N1 is a member of the Orthomyxovirus family. It has recently caused deaths in domestic cats in Germany and in large cats (tigers and   leopards) in Thailand.

Very little is known about this virus in cats at present, and so these notes are simply a summary of present knowledge at time of writing.

Clinical signs

Clinical signs in cats: pyrexia, lethargy, conjunctivitis, protrusion of nictitating membrane, laboured breathing, pneumonia, rapid death.  Clearly there are many other, far more common, causes of similar clinical signs in cats.

Clinical signs in humans: conjunctivitis has been a big feature of this infection in humans, other than that, signs are typically those of flu.

In the USA, testing of HUMANS for avian influenza A (H5N1) is only considered by the CDC on a case-by-case basis in consultation with state and local health departments for hospitalized or ambulatory patients with:

- documented temperature of >38°C (>100.4°F), AND
- one or more of the following: cough, sore throat, shortness of breath, AND
- history of contact with poultry (e.g., visited a poultry farm, a household raising poultry, or a bird market) or a known or suspected human case of influenza A (H5N1) in an H5N1-affected country within 10 days of symptom onset.



See the list of OIE recommended laboratories at the foot of this page.

Curiously the websites of the recommended laboratories are rather shy of saying which samples should be submitted, so here is my recommendation: send an oropharyngeal swab from the living and pieces of pneumonic lung from the dead, in clean receptacles. The main diagnostic tools being used are PCR. It goes without saying that you should take every precaution to protect yourself whilst obtaining the sample - wearing gloves, white coat, face mask. You should also spray the outside of the receptacle with surgical spirit or some other disinfectant, then double bag it securely, before sending it off. Contact DEFRA or your country's appropriate ministry for advice.


There is no evidence that neuraminidase inhibitors such as oseltamivir (Tamiflu) would work in cats, it didn't work in the tiger outbreak and there are many reports of strains of H5N1 resistant to oesltamivir having developed in humans.  Whether oseltamivir causes side effects in cats is unknown. Probably Virbagen Omega injections (1MU/kg s/c daily or e.o.d) and broad spectrum antibiotic cover is as good as anything at this stage.

Prevention of avian influenza virus infection in cats and humans

The zoo cats were infected by being fed raw chickens.  Orthomyxoviruses are enveloped viruses and therefore do not survive well in the environment; hours rather than days; therefore indirect transmission can only occur shortly after the virus is shed, but is unlikely to be a problem after several days.

General advice to cat owners would be:

  • avoid feeding cats uncooked poultry meat
  • if there are many deaths amongst local wild birds, keep your cat in until further information is available

Vaccination of cats against avian influenza virus

A fowlpox vaccine expressing the H5 haemagglutinin gene (Trovac AIV-H5, Merial) has shown immunogenicity in cats (Karaca et al, 2005). 

Risk to humans

There is currently no evidence that cat to human transmission occurs.  Human cases have mainly been in people in the poultry industry.  However, if a suspect case occurred, one would take stringent hygiene precautions and isolate the cat. Virus is shed in oropharyngeal secretions and faeces of infected cats.

WHO stated on 28th February 2006 that: "There is no present evidence that domestic cats play a role in the transmission cycle of H5N1 viruses. To date, no human case has been linked to exposure to a diseased cat. No outbreaks in domestic cats have been reported. Unlike the case in domestic and wild birds, there is no evidence that domestic cats are a reservoir of the virus. All available evidence indicates that cat infections occur in association with H5N1 outbreaks in domestic or wild birds."  

Further reading

World Health Organisation website

World Organisation for Animal Health

Karaca K, Swayne DE, Grosenbaugh D, Bublot M, Robles A, Spackman E, Nordgren R. 2005. Immunogenicity of fowlpox virus expressing the avian influenza virus H5 gene (TROVAC AIV-H5) in cats. Clin Diagn Lab Immunol. 12(11):1340-2.

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Controlling respiratory infections in catteries

There really isn't room on this page to cover all aspects of control of respiratory disease in catteries and you will find it covered in much more detail in my e-books. The best way to prevent respiratory disease in catteries is to construct the cattery in such a way as to minimise infectious disease transmission.

People thinking of building a cattery should consult:

The Feline Advisory Bureau Boarding Cattery Officer, 1 Church Close,
Orcheston, Salisbury, Wiltshire. SP3 4RP
Tel/Fax. 01981 621201

for advice on sneeze barriers, pen construction and dimensions to minimise disease spread.


Secondly, hygienic precautions should be used at all times to prevent transmission of infection. A routine should be established whereby susceptible 'clean' animals should be fed and their litter changed first. Older, vaccinated animals should be attended to next and the sick cats last of all. The person tending the cats should not go back to the susceptible cats after dealing with those who are sick. Each cat should be equipped with two sets of litter trays an bowls, so that while one is being cleaned and disinfected, the cat is using the other. The most hygienic catteries will provide an overall, overshoes, boots or a foot bath and rubber gloves to wear when attending each individual pen.

Pens should be thoroughly disinfected between cats inhabiting them, using either Domestos, Virkon, Parvocide or Tego. Pens should be left empty for as long as possible between occupants. All susceptible cats should be vaccinated.

Rescue shelters and boarding catteries should house cats individually, unless they have come from the same home. All cats going in to boarding catteries should be vaccinated against FCV, FHV and Bordetella bronchiseptica, as should cats going into rescue shelters. It may be that the new Merial vaccine, Purevax RC, which has 2 new strains of FCV, will give broader protection against field strains than other vaccines. However, for rapid onset protection, the Heska intranasal vaccine, Ultranasal, could well be more useful in the rescue shelter environment.


Recommended reading:

Feline Advisory Bureau Boarding Cattery Manual

Addie D.D. Respiratory disease e-book for veterinary surgeons

Addie D.D. Control of viral disease in catteries. Kirk's CURRENT VETERINARY THERAPY XIV Edited by: John D. Bonagura, DVM, MS. In press - due to be released in 2007.


Frequently asked questions

How is cat 'flu spread?

Can cats catch 'flu from humans with 'flu?

What are the signs of cat 'flu?

How can cat 'flu be diagnosed conclusively?


Can any other disease cause similar signs?

What are carriers?


How do you prevent spread within a cattery?

Can you breed cats who are cat 'flu carriers?

How is cat 'flu spread?

The main method of spread of the cat 'flu viruses is by direct contact of one cat with another. Large amounts of virus are present in saliva, tears and nasal secretions (feline calicivirus may also be shed in urine and faeces). Thus it can be spread by cats sniffing each other, mutual grooming and sharing feeding bowls. Sneezed droplets may travel 1-2 metres and cat 'flu can spread rapidly through a cattery unless cats are housed individually with sneeze barriers. Both of the cat 'flu viruses are relatively fragile: FCV lasts about a week outside the cat and FHV lasts a day. Plainly, however, these viruses can be spread within a cattery on cages, food dishes, litter trays, people, etc. so good hygiene precautions should be taken.

Can cats catch 'flu from humans with 'flu?
Cats do not usually catch 'flu from humans with a cold or the 'flu, although there may be an element of risk if the human had avian flu strain H5N1. Humans and other animals cannot catch cat 'flu, as caused by feline calicivirus and feline herpesvirus, but immunosuppressed humans (e.g. newborn babies, people with AIDS, people undergoing chemotherapy) may be at risk from cats suffering the less common infections Chlamydophila felis, or Bordetella bronchiseptica (when I was a practicing veterinary surgeon, I was exposed to plenty of each of these and it's never done me any harm! But then my immune system is fairly normal.).

What are the signs of cat 'flu?
The main signs of cat 'flu are as in human 'flu, i.e. sneezing and runny eyes, which may progress to a mucous discharge. Just before sneezing begins, the cat's temperature will increase, sometimes as high as 105 oF. The cat feels ill and is unable to smell his food because of his blocked nose so often he will not eat. Feline calicivirus also causes mouth ulcers which makes eating very painful and may cause the cat to salivate. The lymph nodes under the chin commonly swell up and may be palpable. These signs generally last only for a week or two in adult cats, longer in kittens,and most cats recover.

In very young kittens or immunosuppressed cats (e.g. those co-infected with FeLV or FIV, or on corticosteroid or Ovarid treatment) cat 'flu can progress to severe pneumonia. The kitten or cat loses weight and may not eat for such a long time that he has to be fed by intravenous drip or stomach tube by the veterinarian. The cat will have difficulty breathing and will breathe through the mouth and may make a wheezing sound.

Cats with chronic rhinitis may be immunosuppressed by concurrent FeLV and FIV infection and cats with chronic rhinitis should be tested for these viruses. In the USA, certain fungal infections can also cause chronic rhinitis: cryptococcus, aspergillus and blastomyces but these are very rare in the UK.

FCV is associated with chronic gingivitis (when the gums are red and inflamed). In some cats, FCV has been reported to cause a limping syndrome. Cats are lame on one leg, then another, and are off colour and have a high temperature but do not necessarily have respiratory signs. In rare cases this syndrome occurs a few days to a week after vaccination and may be caused by the FCV in the vaccine. This condition generally disappears in a few days.

How can cat 'flu be diagnosed conclusively?
Diagnosis of cat 'flu can be confirmed by your veterinary surgeon sending a throat swab in viral transport medium to a veterinary laboratory where the virus will be identified.

Can any other disease cause similar signs?
Chlamydophila and Mycoplasma felis infections also cause conjunctivitis and may be mistaken for cat 'flu. Bacterial infections can sometimes appear like cat 'flu, the chief culprits are Bordetella bronchiseptica and Haemophilus felis. Both are often responsible for outbreaks of coughing which can pass round a cattery in the summer. Bacteria can take the opportunity of a cat's respiratory system being weakened by cat 'flu viruses to infect the cat. In early feline coronaviral infection, catteries often report a transient, mild 'flu-like condition passing through the cats despite the cats having been vaccinated.

What are carriers?
After cats have been infected with cat 'flu viruses, whether, or not they have shown clinical signs, they continue to excrete virus. ln FHV, the carrier state will be lifelong, even in spite of vaccination. Cats do not shed FHV continually but shed it intermittently, particularly in times of stress, for example, when they are rehomed or go to boarding catteries or cat shows, when they have kittens or if treated with corticosteroid. Virus shedding begins about a week after the stress has taken place and lasts for one to two weeks. Animals may show mild signs of cat 'flu at the time.

If mother cats have only low levels of anti-FHV antibodies in their milk, their kittens may be protected from showing disease but are not sufficiently protected not to get infected, so that they can become carriers without having shown disease.

Carriers of FCV, by contrast, shed virus continuously. However, they may recover spontaneously and eliminate the virus. FCV is present in 8 per cent of household pets, 25 per cent of cats at cat shows, 40 per cent of colony cats and 100 per cent of cats with chronic gingivitis.

There are many vaccines available for cat 'flu. Kittens are routinely vaccinated from eight to nine weeks of age, receiving a second dose at 12 weeks old, or three weeks after the initial injection. Cats should receive a booster dose at a year old, and every 3 years thereafter.

Are there any side effects to the vaccines?
Most vaccines have no side effects whatever but some cause mild sneezing and watery eyes for a few days. As stated above, some vaccines have been associated with limping.

Why does vaccination sometimes appear not to work?

If a vaccine is used when the cat is already incubating cat 'flu, it will not benefit the cat. This is sometimes why vaccines appear not to work or appear to cause the condition. It is often a good idea to keep a new cat for one or two weeks before vaccinating him so that any diseases he is incubating will have time to show.
Vaccination of FHV is straightforward because there is only one type of FHV. However, there are many different types of strains of FCV and vaccination will not necessarily protect against all of them.

Can a cat showing clinical signs be vaccinated?
Cats with acute clinical signs of cat 'flu should not be vaccinated.

Can a carrier cat be vaccinated?
Carrier cats can be vaccinated with no ill effects, but vaccination will not stop them from excreting the virus.

Can you breed cats who are cat 'flu carriers?
Cat breeders often have difficulty eliminating cat 'flu from their stock. One regime is to wean kittens early, at three to four weeks, when the antibodies they will have received in the colostrum will be declining. The kittens should be isolated and vaccinated every three weeks until they are 12 weeks old.

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Recommended laboratories:

This list is unfortunately nowhere near complete and I apologise if your country is missed. Scandinavian countries usually send their samples to Companion Animal Diagnostics in Scotland, UK.


Scanelis laboratory, which is attached to the Ecole Nationale Veterinaire Toulouse - for quantitative RT-polymerase chain reaction to detect FCV, FHV, Chlamydophila felis and Bordetella bronchiseptica.


Zurich Veterinary School which pioneered many veterinary quantitative PCR tests to detect virus.


Companion Animal Diagnostics, University of Glasgow Veterinary School - who perform virus isolation, this is especially useful for feline calicivirus infection and will detect the occasional pox which can present as oral ulceration clinically indistinguishable from FCV infection. Telephone them on 0141 330 5777 or email Companion, to order viral transport media, swabs and sample submission forms. Their charge is £13.00 plus VAT. You may also wish to send a biopsy of the lesion in 10% formol saline (from £18.00 plus VAT). For Chlamydophila felis PCR, their charge is £25.00 plus VAT.

For FHV PCR in the UK:

Langford Veterinary Diagnostics ®
School of Clinical Veterinary Science, Langford House, Langford, Bristol, BS40 5DU
Tel: 0117 928 9412  Fax: 0117 928 9613   www.bris.ac.uk/acarus

For suspected Avian Influenza virus infection, use the Veterinary Laboratories Agency.


In America, the quantitative PCR tests which I would recommend you use is available from Dr Christian Leutenneger's laboratory, the Lucy Whittier Molecular and Diagnostic Core Facility, at the University of California, Davis. You can download a sample submission form from his website.


List of the OIE reference laboratories for Avian Influenza





Dr Ortrud Werner
National Reference Laboratory for Highly pathogenic avian influenza and Newcastle disease, Institute of
Diagnostic Virology, Federal Research Centre for Virus Diseases of Animals (BFAV)
Insel Riems, Boddenblick 5a, 17493 Greifswald - Insel Riems
Tel: (41) 383.517.152 Fax: (41) 383.517.151
Email: ortrud.werner@rie.bfav.de

Dr Ian Brown
VLA Weybridge
New Haw, Addlestone, Surrey KT15 3NB
Tel: (44.1932) 34.11.11 Fax: (44.1932) 34.70.46
Email: i.h.brown@vla.defra.gsi.gov.uk

Dr Paul W. Selleck
CSIRO, Australian Animal Health Laboratory (AAHL)
5 Portarlington Road, Private Bag 24, Geelong 3220, Victoria
Tel: (61.3) Fax: (61.3)
Email: paul.selleck@csiro.au

Dr B. Panigrahy
National Veterinary Services Laboratories
P.O. Box 844, Ames, IA 50010
Tel: (1.515) 663.75.51 Fax: (1.515) 663.73.48
Email: brundaban.panigrahy@aphis.usda.gov

Dr Ilaria Capua
Istituto Zooprofilattico Sperimentale delle Venezie, Laboratorio Virologia
Via Romea 14/A, 35020 Legnaro, Padova
Tel: (39.049) 808.43.69 Fax: (39.049) 808.43.60
Email: icapua@izsvenezie.it

Dr H. Kida
Graduate School of Veterinary Medicine, Hokkaido University, Department of Disease Control
Kita-18, Nishi-9, Kita-ku, Sapporo 060-0818
Tel: (81.11) 706.52.07 Fax: (81.11) 706.52.73
Email: kida@vetmed.hokudai.ac.jp


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Download upper respiratory disease in cats e-books

There are two respiratory e-books, one for under- and post-graduate veterinary surgeons, and the other for non-veterinarians. Each costs 5 Euros, Dollars, or GBP.

Respiratory disease e-book for veterinary surgeons

Download an e-book on feline infectious upper respiratory disease and feline chronic lymphocytic plasmacytic gingivostomatitis (note this e-book is only for undergraduate and postgraduate veterinary surgeons, especially those studying for feline or small animal medicine certificates or for continuing professional development. The e-book is not worded for non-veterinarians). In addition to everything contained on this webpage, the e-book contains tables of differential diagnoses, a section about infectious respiratory disease control in catteries, details about feline vaccination and treatment, the truth about azithromycin, notes on less common upper respiratory infections of the cat and more extensive lists of references and websites for further reading.

To buy in UK pounds
£5.00 GBP:

To buy in US dollars

To buy in Euros
€7.50 EUR:



Respiratory disease e-book for non-veterinarians

Download an e-book on feline infectious upper respiratory disease and feline chronic lymphocytic plasmacytic gingivostomatitis for non-veterinarians. This book is written for the cat guardian, veterinary nurses, cat rescuers and those setting up or running boarding or breeding catteries.




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kite9 May 2006

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