Respiratory Disease In Your Cat And Kitten

Rhinotracheitis Virus Cat Flu or Herpes-1, Calicivirus, Chlamydia, Mycoplasma and Bordetella

Ron Hines DVM PhD

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It is very common for cat owners to acquire a new kitten or cat that arrives with a crusty nose, weepy eyes or a sneeze. Or for those symptoms to develop soon after arrival. Veterinarians call these problems upper respiratory diseases (=URIs) because in the majority of cases, your cat’s lungs are not effected – just its nose, sinuses, pharynx and eyes. It is rare for its lower trachea and lungs to be effected. Others refer to the problem as feline respiratory disease complex because it is common for more than one type of infectious organism to be responsible. These feline URIs are one of the most common problems veterinarians deal with.

Like the colds we suffer from, cat URI problems that develop in recent arrivals usually resolve – with or without treatment – in a week or two in their new lower stress homes. But a few cases linger. There are several organisms that have the ability to cause this disease.

What Are The Causes Of Upper Respiratory Infections In Cats?

The most common cause by far is the Feline Herpes 1 virus (aka FeHV-1, cat flu virus, rhinotracheitis virus, gripa felina, katzengrippe, etc.). Just the fact that it goes by so many names gives you an indication of how common it is. This cat virus has a cousin that affects only dogs. (read here) Much more distant herpes relatives affect people. (read here) The herpes-1 cat virus is past from cat to cat most commonly through a sneeze. This virus is relatively fragile compared to other cat viruses. So it rarely lives long enough outside of a cat to contaminate objects or the cat’s living premises. In a new, previously unexposed cat, the virus quickly (~24-48 hours) multiplies within the cells lining the new cat’s nose and upper airways (its respiratory epithelium ). Often the cell-covering surrounding your cat’s eyes (its conjunctiva) are also affected. The feline and similar herpes virus prefer those locations because the passage of room and outside air keep those areas slightly cooler than a cat’s inner core body temperature. (read here) Although the virus persists indefinitely within your cat’s body, these initial infection signs often last 1-3 weeks in otherwise healthy cats. Feline Herpes-1 cases are often more severe when other respiratory disease producing pathogens are also present. Those more complicated cases occasionally leave your cat with epithelial cell lining defects and lingering infections within their fragile nasal bones. That is the most common cause of chronic relapsing rhinitis and sinusitis in young adult cats. It is extremely difficult for your veterinarian to permanently cure these nasal bone infections. In older cats, a variety of potential nasal tumors complicate the diagnosis. (read here)  Others cats are just left with a chronic conjunctivitis that tends to come and go with stress. Still others with corneal ulcers that refuse to heal (indolent ulcers). When they do heal white scars are left. (read here) Between episodes, the virus  silently dwells in the  nerve ganglia of your cat’s face. Most scientists believe that once infected, a cat is never entirely free of herpes virus. The virus is just dormant – for a while or forever. Which cats will never show symptoms again, which will relapse under stress and which will develop chronic eye and nose problems is unpredictable.  During relapses, your cat can again spread the virus to other cats. It cannot spread it to you. Corticosteroid medications such as prenisolone have also been known to reactivate dormant feline herpes virus. In one study 70% of cats that changed households showed evidence that the stress of the move had caused them to resumed shedding the feline herpes-1 virus. In another study, 18% percent of mother cats nursing kittens became virus-shedding positive. These queens (mother cats) have protective antibodies against herpes in their milk. Through their milk, they pass those protective antibodies on to their kittens. But in the stressful situations in which most cats reproduce, that maternal antibody level is often insufficient to keep the virus dormant in their kittens. Animal shelters face this problem every day of the year. There is often a lag time of a week or so between the time your cat undergoes a stress and the time it begins to show signs of a herpes relapse. House cats are not by nature a social species. Even something as trivial as a strange cat present in your yard and seen by your cat day-after-day through your living room window is very stressful to a territorial pet. Nasal and ocular discharges during relapses begin as water-like (serous). But with time they tend to become thick and sticky (=mucopurulent).   (read here)

What Are The Rest Of The Organisms That Make The Problem Worse?

The second most common respiratory disease organism is probably Calicivirus. Some might even elevate its rank to first.

Unlike the herpes virus of cats, the feline calicivirus has many mutations that vary greatly in their virulence (their ability to do harm). One study identified 46 feline calicivirus strains (read here) Like the herpes virus, feline calicivirus has a fondness for the cat’s upper respiratory tract. But unlike the herpes virus, there are highly virulent strains of calicivirus that break out of the upper respiratory tract and, via the cat’s general circulation invade other parts of the body. A common location of that damage are in the area of the ears and paw pads. In other cases, the virus reaches the lungs causing pneumonia. In still others, the liver and or pancreas is affected producing jaundice, hemorrhage, vomiting, diarrhea and dehydration.  (read here & here) Many severe cases are accompanied by mouth ulcers and a fetid breath (aka lymphoplasmacytic gingivitis stomatitis complex). These cases can be fatal. (read here) Most cats however recover and the virus can no longer be found in their upper respiratory tract or mouth a month later.  However a number of cats go on to be chronic carriers and potential spreaders of coronavirus. Some theorize that there could even be life-long carrier cats – although that has never been proven. In feral cat colonies it can be assumed that coronavirus is always present. (read here  &  here)

Chlamydia felis

Chlamydia felis (aka Chlamydophila felis)  is a bacteria. Unlike ordinary bacteria, chlamydia is small enough to live within cells of the body, not between them. They are as small or smaller than many viruses. (ask me for Donnett2014) That gives them advantages in avoiding your cat’s immune system. On rare occasions, the organism has been passed from cats to humans (conjunctivitis).  (read here) This organism is very fragile. Because it does not survive for long outside of the cat, it passes from cat to cat primarily through close contact and mutual grooming – not through air systems or contaminated objects. There is very little known regarding the ability of Chlamydia felis to cause disease on its own. But it has been isolated from about 30% of cats that are experience chronic conjunctivitis. Cats in multi-cat  households, purebred cats and cat under one year of age appear to be at higher risk of being positive for ocular chlamydia. The incubation period before conjunctivitis appears is thought to be 2-5 days. It may start out as squinting and lacrimation (excess tears) in one eye. But with time it is almost certain to spreads to the other eye. The cat’s “third eyelid” its nictitating membrane, usually extends to cover the nasal-most portion of the eye in reaction to the inflammation the virus produces. (read here) In severe cases, the consistency of the tear material might thicken. Cats with a chlamydia eye infecting generally remain bright, cheerful and continue to eat. The organism generally limits its presence to the cat’ eyes and does not involve its nose or mouth. There have been a few cases where corneal ulcers and inflammation led to permanent blindness. But those cases were probably due to the cat rubbing its itchy eyes. 

Mycoplasma and Bordetella organisms make up the rest.

Mycoplasma felis aka M. haemofelis was traditionally called Haemobartonella felis. This organism, like chlamydia, is quite small. Fleas are thought to be the primary way these parasites transfer from one cat to another. Some strains have a preference for your cat’s red blood cells. Those strains results in anemia (haemotrophic mycoplasma). The disease produced is called feline infectious anemia or FIA. Research scientists are always keen to discover a new pathogen, to have the privilege of naming it and a new scientific publication added to their resume. So there is constant bickering and name changing regarding cat mycoplasmas: M. haemofelis, M. haemominutum, and M. turicensis and hemoplasmas are some of the names that have been suggested. I would not pay attention these debates as they have nothing to do with your cat.

There is another group of feline mycoplasma that have an affinity for your cat’s upper respiratory tract and eyes. These the non-haemotrophic strains. Names proposed for them are M. arginini, M. arthriditis, M. canadense, M. canis, M. cynotis, M. feliminutum, M. felis, M. gatae, M. hyopharyngis, M. lipophilum, M. pulmonic and M. spumans. Don’t pay any attention to those names either. Many are probably duplicates of the same organism and others identification errors. Just realize that some mycoplasma of cats prefer living in your cat’s red blood cells and others prefer its respiratory tract and eyes. Since respiratory tract mycoplasma can be found in the respiratory tract of normal cats, it is really unclear if their presence there really important. I would relegate them to opportunists that take advantage of cats that are already stressed by other health and environmental issues. (read here)

Bordetella bronchiseptica is another small bacteria that resides in the respiratory tract of many animal species including cats. When it affects dogs, it is one of the organisms implicated in kennel cough. Bordetella infection is also a common upper respiratory problem in swine. Like, it prefers to dwell in ( colonize) areas that are slightly cooler than than the animal’s inner environment.  Over the years, bordetella has become resistant to many antibiotics because of its ability to produce biofilms. (read hereDoxycycline is currently the antibiotic of choice (must never be given to cats unless tablet is crushed and followed by water). There have been a few recorded cases of Bordetella bronchiseptica infecting people. But those cases are quite rare and generally occur in people with suppressed immune systems (immunocompromized). Although Bordetella is usually spread from cat to cat by direct contact with nasal and oral secretions, one study performed long ago found that the organism could survive up to 5 month in the environment when dry and at room temperature and that it was resistant to repeated freezing. (R.F.Ross1965) Mother cats pass their resistance to B.  bronchiseptica to their kitten through their colostrum. However that maternal immunity subsides over a period of 2-8 weeks. So older kittens can be presented with sneezing, eye discharges and even coughing and breathing difficulties with this organism being involved.  These usually resolve over 7-12 days, but cats continue to spread the organism considerably longer – perhaps indefinitely. (read here  & here) Once utensils and the cat’s environment are cleaned with soapy water, ordinary household bleach rapidly kills bordatella. 

Can I Tell Which Organisms Are Causing My Cat’s Problem From The Signs I See?


Your vet can’t either, unless the tell-tail whitish corneal scars of a relapsing Herpes-1 infection are already present. (read here) And even then, multiple organisms could still be present. When cats first come down with these diseases they often run a fever, sneeze and become listless. Their appetite may wane. After the first few days of illness their body temperature returns to normal. A cat’s normal body temperature is 101.5-102.5 F (38.6-.39.2 C). Cats with first-time respiratory tract infections can reach 106 F (41.1 C) during their first few days of illness. That is why your cat’s adequate fluid intake is so important to prevent dehydration. Cats with Calicivirus often drool due to ulcers on their tongue, lips and the roof of the mouth. These cats rarely show signs of pneumonia because with the exception of Calicivirus, these organisms usually spare the lungs. Nasal drainage is at first watery. With time, the discharges become thick, tenacious and mucoid. In cat’s with eye involvement their eyes become reddened, inflamed and weepy. These signs can last a week or so in mild cases and many months in stressed cats, frail cats and immunosuppressed cats that are positive for FLV or FIV. Mature and semi-mature cats almost never die from this disease. It is only life threatening in weak kittens that might stop eating or when secondary pneumonia occurs in weakened patients. 

What Are Some Things That Will Speed My Cat’s Recovery?

Although veterinarians including myself are most likely to prescribe an oral antibiotic such as doxycycline for your cat (read here) , viruses are not killed by antibiotics. So only when your cat’s problem includes chlamydia, mycoplasma or bordatella co-infections are antibiotics actually curative. Veterinarians put these cats on antibiotics because we are never sure which pathogens are present and to prevent secondary pneumonia and sinusitis in debilitated patients.

I have found that most cases of upper respiratory disease complex responds well to simple T.L.C. Boiled chicken served as a soup is an excellent treatment for this disease. You can be fed through an eye dropper if need be to prevent dehydration and to tempt your depressed cat into eating. Pungent foods such as sardines and tuna will often be accepted when other diets fail. I place these cats on a liquid multivitamin supplement as well because so many of them are stressed, not eating or only willing to eat an unbalanced diet. Cats that are severely congested seem to do well with vaporizers, steam and nasal decongestants. I also dispense tetracycline eye ointment to lubricate the eyes and crusty, painful nostrils. When it causes your cat to have a poor appetites high caloric products such as Nutrical®, Hills Science Diet A/D or Royal Canin’s Recovery can be helpful as well. Plump cats that won’t eat are subject to hepatic lipidosis

Is There A More Specific Treatment When Feline Herpes-1/ Rhinotracheitis Virus Is Involved?


The Best Medication Veterinarians Have today to treat Feline Herpes-1 infections and its later flare-ups is famciclovir (Famvir®). Read about that medication here and here. This medication, now available in generic 125, 250 and 300 mg tablets, is bitter. In one of those studies, 40 mg/Kg, given three times a day for an average of 40 days appeared to be as effective as 90 mg/Kg given at the same frequency. You might have more success purchasing a better tasting formula from a custom pharmacy such as Wedgwood. They sell famciclovir in tasteless capsules, chew treats, an oral powder and in combination with doxycycline or azithromycin in case bacterial organisms such as mycoplasma or bordatella are also involved in your cat’s issue. 

There was a time when veterinarians including myself thought that an amino acid, l-lysine, supplement might be helpful to some of these eye-related cases in cats. That was based on the finding that consuming lysine appeared to be helpful for people with herpes sores. (read here) Theoretically, it was proposed that lysine reduced the amount of another amino acid, arginine, that the virus required to multiply. However more recent studies found that lysine did not have this effect in cats and probably is ineffective in humans as well. (read here  &  here)

Carrier Cats

A small portion of cats infected with this herpes virus aka rhinotracheitis will lapse into a chronic carrier state that lasts for years or for a lifetime. Most of these carrier cats show no signs of the disease, but some are subject to intermittent eye inflammations, and draining nostrils – usually brought on by stress. Others develop milky lesions of their corneas that come and go. In their inactive states, these eye lesions are milky white circular scars within the cornea. We call this disease herpetic keratitis. When rhinotracheitis flares up as corneal ulcers many cats squint and tear as their outer eye membranes become inflamed. As I mentioned, these flare ups are often associated with the stress of boarding, weather changes, other diseases or new cats in the family. 

Are There Ways To Prevent This Viral Problem?

Good vaccines are available to prevent this disease. See two of them here: &  here:   I give these vaccines to kittens at 8 or 9 weeks of age and again at 10 – 12 weeks of age. The problem is that many kittens are already infected with the virus of rhinotracheitis before their first vaccination. The stress of pregnancy and nursing causes some herpes carrier mothers to relapse and pass the virus on to their kittens. Many cats from shelters are in the middle of an infection when I first see them. In these instances the vaccine is not effective. Manufacturers suggest yearly revaccination but there is evidence that rhinotracheitis and calicivirus vaccines may not need to be given that frequently. When they are given, I administer  the vaccine through a 25-gauge needle on the front or anterior side of a rear leg or the tail and then massaged the injection site. This perhaps decreases the very rare instances where tumors forms at vaccine injection sites in cats. (read here)

Within the last few years, veterinarians have been given a tremendous tool for sorting out the various organisms that can cause respiratory problem in your cat. (read here) Sophisticated central laboratory services are now available throughout the United States to do this. All utilize a very sensitive test, the Polymerase Chain Reaction or PCR test to look for six of the most common causes of upper respiratory and/or chronic eye problems in cats ( bordetella, chlamydia, calicivirus, herpes 1 and mycoplasma). One limitation of the panel is that the most common cause of reoccur rent sneezing, the Herpes-1 (rhinotracheitis virus), is so stealthy that it can even avoid detection with the PCR test when your cat is not experiencing a virus flare-up. So if the PCR test is positive for herpes-1, your cat is definitely a carrier of the virus. But if it is negative, the virus might still be sleeping somewhere deep in your cat’s nervous system cells. If the test found no likely cause reoccurring upper respiratory tract or eye problems, you might consider having the test repeated at a later date – preferably during a flare-up.

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