Cat Flu



Cat Flu
Cat flu is very common in unvaccinated cats and is very easily spread from cat to cat. It is rarely fatal, except in young kittens, but can be a real problem because the symptoms may be very difficult to clear up. Prevention is far better than cure - so to protect your cat make sure she is fully protected by regular vaccinations.

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. The most serious cases are caused by FHV.

Symptoms include sneezing, nasal discharge, conjunctivitis (inflammation of the lining of the eyes), discharge from the eyes, loss of appetite, fever and depression. Occasionally, mouth and eye ulcers and excessive drooling of saliva may be seen. The very young, very old and immunosuppressed cats are more likely to develop severe disease and possibly die as a result of their flu. Where death occurs this is usually because of secondary infections (infections with bacteria in addition to the flu viruses), lack of nutrition and dehydration.

Cat flu is usually caused by infection with a combination of one or more viruses (feline herpesvirus and feline calicivirus) and some bacteria. If one of the viruses gets hold then your cat's immune system may be so busy fighting it that other bugs (particularly bacteria) will also join in the attack.

Rather like human flu, cat flu is spread by droplets of moisture containing the virus, passing from cat to cat - through sneezing, direct contact or shared food bowls. Infected cats spread virus in the saliva and nasal discharges (snot). The incubation period (the time for which a cat is infected and carries the disease before the symptoms develop) is up to 3 weeks. This means that it is quite possible for your cat to pick up the disease from another cat which seems healthy. People can spread the virus from cat to cat when handling them.

Cat flu is most commonly seen in situations where cats are kept in large groups such as breeding catteries, rescue centres and feral cat colonies, although it can also be seen in pet cat households. Cats most at risk include unvaccinated cats, kittens, the elderly and cats which are immunosuppressed for any reason. In immunosuppressed cats, damage to the immune system has left them vulnerable to a wide variety of diseases with which they would otherwise be able to cope. Immunosuppression can be seen in cats infected with feline leukaemia virus (FeLV) or feline immunodeficiency virus (FIV), cats with other severe illnesses, or in those receiving treatment with certain medications such as corticosteroids or anti-cancer therapy. Although vaccination helps to reduce the risk of cat flu, this disease can still be seen in vaccinated cats.

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.

But cats cannot catch 'flu from humans with 'flu nor can humans or other animals catch cat 'flu.

Cat Flu Symptoms

The signs of cat flu are very obvious and unlikely to be mistaken for anything else. In fact cat flu is often very similar to human flu starting with a high fever which may make your cat feel miserable and off her food, followed by the sneezing, coughing and sore eyes. Signs usually start to get better after about 7 days and, in most cases, your cat should be back to her old self in about 2-3 weeks. In some cats the disease can cause ulcers in the mouth making eating difficult.


Feline herpesvirus (FHV) infection often causes severe and potentially life-threatening illness. Although the majority of cats infected make a full recovery, this often takes several weeks and some cats are left with permanent effects of infection such as chronic rhinitis. Cats with chronic rhinitis are usually well in themselves but have a persistent discharge from the nose and sneeze. Secondary bacterial infection of damaged tissue can cause chronic conjunctivitis, sinusitis and bronchitis (inflammation of the linings of the eye, sinuses and air passages). Antibiotic treatment usually only provides temporary relief of these symptoms.

Feline calcivirus (FCV) infection usually causes a milder form of cat flu with less dramatic nasal discharges. Characteristic mouth ulcers are sometimes the only sign of infection. The ulcers may be present on the tongue, on the roof of the mouth or the nose.

Some strains of FCV cause lameness and fever in young kittens (these can occasionally be seen after vaccination). Affected cats recover over a few days although they may need pain killers through this time. More recently a more virulent strain of FCV has been identified in the USA. This strain causes severe swelling of the face and paws and has a deleterious effect on the whole body with a high mortality rate (40%). Further investigation into this strain strain is currently ongoing.

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. FCV 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 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.

In very young kittens a few days old or 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.

FHV can cause ulceration of the cornea (the front of the eye) and, if left untreated, the eyeball may rupture. Some kittens who have bad 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 mucous nasal discharge and sneezing. One or both eyes may be distorted by adhesions from the eyeball to the inner eyelid.

Cats with chronic rhinitis are often immunosuppressed by concurrent FELV and FIV infection and cats with chronic rhinitis should be tested for these viruses.

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.

Cat Flu Treatment

Most fit young cats will recover from flu after a few weeks - although in a few cats that do get over the initial illness the problem never really goes away. These animals may be left with persistent problems such as runny noses.

There is no treatment for flu in cats. Your cat will have to fight off the infection by herself and fortunately most, otherwise healthy cats, will do this within a few weeks. But cats, just like people, feel pretty miserable when they have the flu and plenty of nursing care is needed to help her get over it. Make sure she has somewhere comfortable and warm to lay and be sure she gets plenty of water or milk to drink. Although your cat may not want to eat for the first few days, you should try to tempt her to eat by offering tasty warm food to keep her strength up. You should always have your cat checked by your vet, and antibiotics may be prescribed to treat bacterial infections. If your cat is very congested try putting her in a warm steamy environment (like the bathroom with a hot shower running) to ease her breathing.

Owners 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.

Cats with chronic rhinitis are notoriously difficult to treat. Many have to take antibiotics all 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 involved, the amino acid lysine can be added to their food.

The disease can be much more serious in young kittens, older cats and cats with other diseases, eg FeLV or FIV - these patients may need to be admitted to hospital for special treatment but, even so, may not survive.

Most cats that recover from cat flu become 'carriers'. Carrier cats usually show no sign of illness themselves but, by shedding virus in their saliva, tears and nasal secretions, are a source of infection to other cats. FHV carriers shed virus in their secretions intermittently. Shedding tends to occur following times of stress, such as a stay in a boarding cattery, and may or may not cause some recurrence of flu signs such as sneezing and nasal discharge in the carrier cat. Treatment for other diseases using corticosteroids may also precipitate an episode of virus shedding. Cats that are FHV carriers remain so for the rest of their life. In contrast, most cats infected with FCV shed the virus continuously for a short time after recovering from flu and then virus shedding stops. In a few cats FCV shedding continues for several years.

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.

Cat 'flu viruses are spread in three ways:

* Direct contact with an infected cat showing signs of flu.

* From contact with virus carried on clothing, food bowls and other objects. Large amounts of virus are present in the saliva, tears and nasal discharges of cats with 'flu. The virus is able to survive in the environment for up to a week.

* From contact with a cat that is a carrier of cat flu. Breeding carrier cats are a risk to their kittens as the stress of kittening may precipitate shedding of FHV and infection of the kittens with either FHV or FCV may occur before the kittens are old enough to be vaccinated.

Preventing the spread of infection in a multi-cat environment involves 'barrier nursing' of infected cats. The infected cat should be isolated from the other cats, for example kept in one room of t he house, where it can be treated without the risk of spread of virus to other cats in the household. Separate food bowls and litter trays should be used for this cat. These should be disinfected with a product which kills the virus but is safe to cats, as recommended by a veterinary surgeon. In a cattery, one person should look after the ill cat, and they should disinfect their face and hands and change their clothes or overalls when leaving the cat in isolation. If one person cares for all the cats, the infected cat should be handled last of all the cats in the home.

The risk of developing cat flu can be reduced by regular vaccination against FHV and FCV. These vaccines stimulate the cat's immune system helping it to fight infection and protect it from developing disease. However, although vaccination usually prevents severe disease developing, they are not always 100% effective against preventing infection and mild disease may still occur in some cats. FCV has several different strains and work is still ongoing to develop more effective vaccines. Recently some newer vaccines have been marketed, which include cover against some of these more recently recognised strains.

The sensible precaution is to have your cat vaccinated to stop her getting flu in the first place. The flu vaccine that is given routinely as part of the annual vaccination programme will protect your cat against the common agents that cause serious disease. Vaccination does not always prevent infection, but it usually stops severe disease developing.

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 yearly booster dose.

Cats with acute clinical signs of cat 'flu should not be vaccinated. Carrier cats can be vaccinated with no ill effects, but vaccination will not stop them from excreting the virus.

It is advisable to vaccinate all household cats, especially if the cat goes outdoors, stays in a cattery or goes to cat shows. If an individual develops cat flu, subsequent stress, such as attending a cat show, should ideally be avoided.
Breeding cats should be vaccinated before they are mated so that they produce high levels of antibody in their milk.

These maternal antibodies only protect the kittens until they are about 4 - 8 weeks old, after which the levels of antibody gradually disappear. Kittens can only be vaccinated successfully when the levels of antibody have disappeared at between 6 and 12 weeks of age.

Cats that recover from infection with FHV or FCV may be able to resist future infections (be immune) for up to a year or more. As there are many strains of FCV, a cat that recovers from infection with one FCV strain can still subsequently be infected with another. Vaccines use strains of FCV which give the most cross-protection to other strains, to try to provide as broad a protection as possible against this infection. This is not an issue with FHV as only one virus strain exists.

Preventing the spread of infection in a multi-cat environment involves 'barrier nursing' of infected cats. The infected cat should be isolated from the other cats, for example kept in one room of t he house, where it can be treated without the risk of spread of virus to other cats in the household. Separate food bowls and litter trays should be used for this cat. These should be disinfected with a product which kills the virus but is safe to cats, as recommended by a veterinary surgeon. In a cattery, one person should look after the ill cat, and they should disinfect their face and hands and change their clothes or overalls when leaving the cat in isolation. If one person cares for all the cats, the infected cat should be handled last of all the cats in the home.