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Cat Flu - Upper Respiratory Infections
(URI)
Cat flu is a common disease in cats of all ages despite
widespread vaccination, but tends to be particularly severe
in young and old cats. A number of infectious agents have
been found to cause cat flu, but the vast majority of cases
will be caused by one of two viruses, feline herpes virus
type 1 (FHV-1) and feline calicivirus (FCV). FHV-1 is also
known as feline rhinotracheitis virus.
What are the clinical signs of cat
flu?
Signs of cat flu are similar to colds and flu in people.
FHV-1 tends to cause more severe disease, the major signs
are inflammation of the lining around the eye
(conjunctivitis) and nose (rhinitis). This causes a clear
discharge from the nose and eyes which becomes thickened and
purulent as the disease progresses due to secondary
bacterial infection. Cats tend to be dull and depressed with
a raised temperature, sneezing and are reluctant to eat.
Coughing is also a feature in some cases. Rarely the virus
will cause skin lesions and invade the lungs causing
pneumonia. Without treatment signs usually resolve in 2-3
weeks but some cats are left with a chronic, intermittent
nasal discharge or eye disease.
FCV tends to cause less serious disease, but clinical signs
are dependent on the strain of virus that is involved. Mouth
ulceration can be a prominent feature of the disease causing
severe inappetance. Ulcers may also sometimes occur on the
tongue, nose and hard palate. Some strains of FCV cause a
lameness and fever syndrome in young kittens. FCV is
commonly isolated from cats with long-standing (chronic)
inflammation of the gums (gingivitis) but the precise role
of the virus remains unclear.
Deaths following respiratory virus infections are rare,
usually occurring in young kittens or old cats that have
advanced disease before being presented for treatment.
How is cat flu diagnosed?
In most cases the diagnosis is made on clinical signs but in
cases where there is recurrent disease or in vaccinated cats
a specific diagnosis may be required. This can be achieved
by swabbing the cat's mouth and sending the swab in viral
transport medium to a laboratory where the virus can be
grown in culture and identified.
What treatments are available?
As for colds and flu, specific antiviral treatments are not
generally available. Treatment is aimed at controlling
secondary bacterial infection (with antibiotics) and
stimulating eating and drinking as, particularly
dehydration, is a major cause of worsening disease.
Antiviral ointment (e.g., acyclovir) used to treat herpes
virus infections in people (cold sores, fever blisters) has
been used in cats, generally the response is not as good and
the drug needs to be used early in the course of infection.
Its use tends to be restricted to treatment of FHV-1
outbreaks in colonies of cats. Topical antivirals include
Idoxuridine and Betadine eye drops. L-lysine (an amino acid)
works to prevent future attacks in some cats. L-lysine can
be purchased over-the-counter at health nutrition stores.
What can be done to help treatment?
Your cat can be encouraged to eat and drink using drugs such
as multivitamins and mucolytics (helps dissolve secretions)
but good nursing plays a crucial role. The eyes and nose can
be kept clear of secretions by gently bathing the area with
cotton wool and by steaming. Steaming needs to be undertaken
carefully. The cat is placed into the bathroom, with the
shower as hot as it will go, then the is filled sink with
equally hot water. Since the running water sounds may be
very upsetting to the cat, stay in the room, grooming and
softly speaking to him to keep him calm. The steam acts to
loosen secretions making the cat feel better. Your cat can
be encouraged to eating by providing highly flavored foods
e.g. sardines warmed to body temperature. Hand feeding can
also help.
Severely ill cats may need additional care at your
veterinarian's hospital; this allows rehydration with
intravenous fluids and feeding by naso-esophagal tube.
How can cat flu be prevented and
controlled?
For most households with a few cats, vaccination is
sufficient. Vaccination will not usually prevent your cat
becoming infected but will drastically reduce the severity
of the disease, often to the point that all that is noticed
is mild lethargy and inappetance for a few days. A variety
of vaccines are available depending on the circumstances
(see speak with your veterinarian). Neither virus is very
hardy, FHV-1 will survive for a maximum of 48 hours in the
environment, FCV lasting 7-10 days.
In multicat households, particularly where new cats are
continually arriving (such as in rescuing or at shelters),
vaccination alone may not be sufficient to control the
problem. In these households isolation and quarantine is
also required. Disinfection, while an important part of
disease control generally, is of limited value in
respiratory virus control as most cats become infected by
aerosol droplets sneezed or coughed out by infected cats.
Clinically ill cats or those suspected of being carriers
should be isolated and handled last. Their food bowls and
litter boxes disinfected and your hands, face, clothing and
shoes washed before handling other cats. If at all possible,
separate clothing should be worn. New arrivals to the group
should be quarantined for 7-10 days in case they are
incubating cat flu. Unfortunately, quarantine will not
identify carrier cats. In households where cat flu is
endemic, queens should be kittened in isolation from other
cats and, where possible, the kittens remain in isolation
until vaccinated.
What are carrier cats?
Carriers are animals that are infected with cat flu but are
not showing any clinical signs. Carriers are only infectious
to other animals when shedding the virus. Viral shedding can
be continual or intermittent. Around 80% of cats that have
been infected with FHV-1 become carriers. They shed the
virus intermittently usually during periods of stress (e.g.
rehousing, lactation) and remain carriers for life. About
50% of cats infected with FCV are still excreting virus 3
months after they were originally unwell. Some of these cats
continue to excrete for up to 18 months. FCV carriers
excrete continually so are always potentially infectious to
unvaccinated cats.
Can I check to see if my cat is a
carrier?
In some special circumstances it may be helpful to identify
carriers but this is not usually important for pet cats. A
swab can be taken from your cat's mouth which will show if
he is a FCV carrier. FHV-1 carriers are only diagnosed if
they are excreting the virus at the time the swab is taken,
which is unlikely.
What should I do if my cat is a
carrier?
Nothing can be done to change the carrier status of your
cat. It is important that your cat does not come into
contact with unvaccinated cats or kittens. All cats that
have had FHV-1 infection should be assumed to be carriers.
My cat has had cat flu. Should I
bother to vaccinate him?
Yes. Your cat is likely to have been infected with only one
of the viruses so will still be susceptible to infection
with the other.
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