Rhinotracheitis In Your Cat = Feline Herpes-1 Virus, Cat Flu

Ron Hines DVM PhD

Additional Info on Feline Herpes/Cat Flu

Herpes Virus Eye Problems

Cat Coughing? 

Cat Sneezing?

Rhinotracheitis is a disease caused by the feline herpes-1 virus. In the UK, it is the most common cause of what is commonly called Cat Flu. Rhinotracheitis is probably the most common infectious diseases of cats in the developed World. Once infected, many believe that recovered cats remains virus carriers for the rest of their lives – usually in a latent or “sleeping” form. Reemergence (recrudescece) of the virus and return of symptoms is a particular problem in high stress environments such as animal shelters, feral cat colonies and households with psychologically incompatible cats. Other stressors are moving, boarding, pregnancy, lactation, injury or surgery.  Overcrowding, poor nutrition, poor sanitation, and the lack of highly effective rhinotracheitis vaccines also make the disease more likely. Some pets continue to have low grade, persistent infections with respiratory symptoms, eye drainage and conjunctivitis.  In one Colorado shelter, evidence of the virus could be found in 93.3% of the cats that were housed there. (read here)

The majority of cats that have recently contracted the rhinotracheitis virus show only mild eye and/or upper respiratory tract symptoms that subside within 8-20 days – with or without treatment. Those with lingering first-time infections probably have other underlying health issues. Those issues could be chronically stressed cats with over-taxed immune systems, FeLV or  FIV positive cats or cats experiencing malnutrition or starvation. The high virus load and exposure common in large group homes and catteries also favor the virus’ spread. In those situations a cat or two is always shedding the herpes-1 virus. In the majority of cats, that initial rhinotracheitis virus exposure occurs in early kittenhood – probably from their virus-shedding mother. That is often earlier than veterinarians or vaccine manufacturers suggest that their rhinotracheitis vaccines be given. Rhinotracheitis vaccines given to cats that already carry the virus are of no value. Genetics might also plays a roll in determining the severity and prevalence of rhinotracheitis. Long-haired cats and purebred cats (Siamese/Burmese?) are perhaps more genetically predisposed to lingering infections than random bred neighborhood cats.

How Is This Virus Passed?

Cats become infected with rhinotracheitis in several ways. The most common way is close exposure to a sneezing cat or a carrier cat showing no symptoms at all – as I mentioned, it is often the litter’s mother. Cat sneezes scatter the virus particles through the air up to 10-12 feet. Curious cats and kittens that approach and sniff an infected cat can also become infected by the virus particles clinging to the second cat’s hair coat. Although not nearly as common, people can also spread the virus on their hands and clothing. Some believe that it is also possible for infected mother cats to pass the virus on to their kittens while the kittens are still in the womb. However most believe that the majority of virus transfer takes place during the nursing period. Once exposed, the rhinotracheitis virus enters the body though the lining of the nose, pharynx, sinuses, throat, windpipe and the cats eyes (conjunctiva). Much of this spread information and the dynamics of infection is conjecture (guesswork) – or based on studies of human herpes simplex virus (HSV-1), a close relative of the cat herpes-1/rhinotracheitis virus. To the best of my knowledge, no controlled studies of how and when the rhinotracheitis virus commonly transmits from cat to cat or cat to kitten have ever been conducted.  

What Happens Then?

A few days after infection or reactivation from a latent infection, many cats begin to sneeze. If it is a young cat or kitten’s first experience with the virus, it might loose its appetite and become depressed. It might be running a fever. The normal body temperature for an adult cat is ~100.4 – 102.5 F (38-39 C). Kittens run a bit cooler ~99 – 101.5 F (37.2 – 38.6 C). It is quite common for these cats to soon develop a nasal and/or ocular discharges. Although signs of sickness during these first exposures are highly variable (no signs to substantial signs), the herpes virus is actually moving throughout their bodies. 

Interference with your cat’s sense of smell might accounts for its lack of appetite. Those cats and kittens might be tempted to eat when temporarily given more pungent smelling and tasting food (ocean fish flavors). Those flavors can be addictive, so confine them to periods of sickness or convalescence.  Some cats develop oral ulcers that dampen their desire to eat. They may also have concurrent infections of feline calicivirus which produces similar mouth and tongue ulcers. These two diseases are often confused. When only feline herpes is the underlying cause any your cat is basically healthy, these problems usually resolve without medications during the following two or three weeks. Although quite rare, if a pregnant cat becomes infected or suffers a herpes relapse, she might abort or reabsorb some or all of the kitten or give birth to a litter in poor health. 

A common residual effect of recurrent rhinotracheitis/Herpes-1 is persistence of the virus in the cornea(s) of a cat’s eye. (read here) During periods of stress, the virus, which lays dormant in nerves of the face, will reactivate forming oval corneal ulcers that are slow to heal. These appear as milky areas on the otherwise clear cornea. When these ulcers are active, small blood vessels can be seen entering the area in response to the inflammation. When they are quiescent, these areas are in effect scars with no specific blood supply. They are the most obvious signs of a cat that is a herpes virus carrier that occasionally relapses. 

Another residual effect of the disease in some cats is chronic rhinitis (nose inflammation) and sinusitis. In these cats, flare-ups of the virus lead to necrotic (non-vital) tissue within their turbinate and ethmoid bones. These necrotic areas of chronic inflammation eventually harbor bacterial infections that are extremely hard for veterinarians to cure. Antibiotics have difficulty reaching those bacteria. With time, the bacterial population causing the infection eventually becomes resistant to whichever antibiotics are being given. Those antibiotic-resistant bacteria are also a threat to your health. (read here  & here)   

How Does My Veterinarian Diagnose A Herpes-1 Virus Infection?

Although we can be highly suspicious that we are dealing with a case of rhinotracheitis, it is not possible to diagnose the disease with certainty from symptoms alone. This is because the symptoms of infection with calicivirus or certain respiratory mycoplasma are too similar. Typically calicivirus does not affect the eyes and mycoplasma affects primarily the eyes. Also, typical, calicivirus and mycoplasma cause less depression, malaise and fever. It is possible for your veterinarian to send cotton swabs of your cat’s nasal secretions and/or eye drainage to central laboratories for Herpes-1 virus isolation – but this is not commonly done. These tests are not particularly accurate. (read here) Even less so when the virus is in its latent, quiescent state. 

What Medications And Treatments Will Help?

Good nursing care, good nutrition and a low stress environment is the most important therapies for rhinotracheitis. Antibiotics might  help prevent secondary bacterial infections nose and eye infections. But they have no effect on the virus. A small amount of human saline nasal spray and/or inhaled steam treatments (nebulizers) often make the cats feel better and make it easier for them to breath. Nasals sprays that contain  phenylephrine or pseudoephedrine pose greater risk. Of the two, those that contain only phenylephrine are the safer of the two, but both can cause agitation/restlessness, increased heart rate and blood pressure, muscle tremors, seizures and even be fatal depending on the dose given. Some veterinarians suggest that gentamycin be added to nebulized steam. Others might give the cat injections of B-complex vitamins in an attempt to stimulate appetite. Some suggest adding extra l-lysine to your cat’s diet, based on perhaps some beneficial effects when given to humans with herpes infections. (read here)

Antiviral Medications

Famciclovir (Famvir®) is a medication used to treat shingles and various forms of human herpes infections. In 2009 several veterinarians in Australia found that giving famciclovir to cats early in active rhinotracheitis/FHV-1 infections improved their outcomes. (read here) Follow up studies in California using famciclovir in more rigid studies in 2011 and 2016 were equally promising. (read here  & here) So if your cat begins treatment with this medication early in its infection or at the beginning of a relapse, it is likely to be ill for a shorter period of time. 

Acyclovir, aka acyclovir, is an older antiviral medication used against human herpes virus. It has also been given to cats in an attempt to shorten their number of relapses or decrease their severity. (read here  & here) Famciclovir is, perhaps, less toxic to cats than acyclovir. But acyclovir’s major drawback is that it persists in the cat’s bloodstream for a shorter period of time than famciclovir and so must be given several times a day which leads to increased chances of overdose and side effects. 

Are There Medications That Might Increase The Chances Of My Cat Having A Relapse?


All medications that weaken your cat’s immune system have been implicated in herpes-1 relapses. Some examples are cyclosporin/Atopica® and all variety of corticosteroids (such as prednisone,   prednisolone,   dexamethasone and methylprednisolone) depending on the dose and  length of time given. All chemotherapeutic medications that suppress your cat’s immune system might have that effect as well. We all have to balance benefits with risk. There will be cases where the benefits of these drugs outweigh their risks. 

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