vaccination, cat flu remains a common problem in many breeding
colonies. The disease is apparently mild in some households
and restricted to a minor outbreak of sneezing that improves
with no treatment. In other colonies, the disease is much
more severe and can leave kittens with chronic disease and
difficult to sell, or cause deaths of individuals or entire
litters. Breeders who do have a problem with cat flu can spend
a lot of time and money on investigation, and even then are
still at a loss with how to control the disease. Cat flu is
an important cause of illness and death in breeding colonies
and its control needs to be approached in a sensible manner.
Good control of flu may involve re-homing or neutering of
some breeding stock.
is cat flu?
Typical ocular and nasal discharges of cat flu
breeders will agree that they know what cat flu is. It is
an infectious respiratory tract disease of cats, often seen
in kittens in the breeding household and seemingly not affecting
the adults. The typical combination of symptoms includes discharge
from the nose and eyes, ulcers in the mouth, reluctance to
eat and drink, sometimes coughing, fever, difficulty breathing
and, rarely, death. Which symptoms occur probably depends
upon a number of factors, including not only the infectious
agent present but also on management factors within the colony.
are many causes of cat flu. Probably the most common are the
two upper respiratory tract viruses, feline herpesvirus (FHV,
also known as feline viral rhinotracheitis [FVR]) and feline
calicivirus (FCV) which, along with a bacterium called Bordetella
bronchiseptica, are most commonly detected in cats with
typical signs of cat flu. Although Chlamydophila disease is
often discussed at the same time as flu, in cats with Chlamydophila
felis infection the signs are almost always restricted
to the eyes and the serious flu signs are not seen.
the most common source of infection for cats in pet homes
is sick cats, especially if the new cat or kitten comes from
a rescue colony or from another pet home where the cats are
unvaccinated. In breeding households the disease can be caught
from sick cats, but also important is the role of the apparently
healthy carrier cat (see below). In order to understand this
it is important to think a little about the individual infections.
Infection with feline herpesvirus infection can cause serious eye damage
is only one 'strain' of FHV and it usually causes severe signs
of flu. Thick secretions can block the nose and glue up the
eyes, needing careful nursing care and antibiotic cover. Kittens
are often very quiet, unable or unwilling to eat and have
a high temperature. Some kittens, or adults with pre-existing
diseases that suppress the immune system (eg, FIV, diabetes,
cancer chemotherapy or on steroid therapy), may die.
infected cats, it can take weeks for the signs to improve.
The virus infection
can cause severe damage to the delicate respiratory and eye
tissues leading to long-term problems such as a chronic rhinitis
(snotty nose) or conjunctivitis (runny eyes). Even in cats
that recover entirely, those that have been infected by FHV
are infected for life, becoming 'carriers' of the infection.
Cats that are carriers of FHV do not shed virus all the time
- it 'hides' in the cat and is only shed at times of stress.
Known stresses that can start a cat shedding virus include
re-homing, going to shows or catteries (including stud), having
kittens or lactating.
studies, carrier cats start to shed virus around one week
after the stress and shed the virus for up to 14 days after
that. Some cats do show mild signs of flu when they are shedding
virus, but many cats have no symptoms at all. It can be hard
to detect carrier cats, as they do not shed virus all the
time, and a negative swab cannot therefore be taken to mean
that the cat is clear. A positive swab on the other hand does
mean that the cat is infected. The virus cannot be eliminated
from carrier cats. As an infected queen will usually infect
successive litters of kittens, probably the best way to manage
cats known to be infected with FHV is to remove them from
the breeding population by neutering and re-homing.
Oral ulceration is common in feline calicivirus
are many strains of FCV, some of which appear to cause more
severe disease than others. In general, FCV usually causes
milder signs than FHV, often restricted to mild nasal discharge,
conjunctivitis and the development of ulcers in the mouth.
Even though these ulcers can be quite large, affected animals
rarely have poor appetite and are usually still quite bright.
In some cases the breeder is not aware that the kittens are
ill. Though severe disease is less common than with FHV, FCV
can still leave the kitten open to bacterial infection and
antibiotics and nursing care are needed.
the virus causes a dramatically different disease, so called
'pyrexia and limping syndrome', where kittens suddenly become
lame on one or more legs and get a high temperature. Though
dramatically ill, kittens usually get better rapidly with
no treatment or with painkillers.
disease associated with FCV infection is gingivitis - inflammation
of the gums. Gingivitis is very common in the pedigree cat
population and many affected cats are found to be shedding
that have been infected with FCV also become carriers. However,
the carrier state for FCV is rather different to that for
FHV. In FCV, recovered cats shed the virus for a variable
length of time, but they do so continuously. Most cats shed
the virus for at least one month after infection, but by two
to three months approximately half of infected cats will have
stopped shedding. As time goes on, the majority of cats do
eventually eliminate FCV, though some cats shed the virus
for years. As shedding is continuous, it is easier to decide
if a cat is a carrier by looking for the virus. It is also
possible to trace a cat to see if/when it stops shedding virus
and may have eliminated the infection. However, because there
are many strains of FCV, it is possible for cats to be infected
several times with different strains, especially if the cat
visits cat shows, seminars, studs, etc. Because the disease
can be mild in adults, in particular if they have met FCV
before or are vaccinated, it is not always noticed that the
cat is ill. An FCV strain that causes mild disease in adults
though, can cause more severe problems in relatively naive
kittens. More recently more virulent strains of FCV have been identified in the USA and UK. Among other clinical signs these strains often cause severe swelling of the face and paws, skin ulcerations on the head and limbs, and jaundice (yellow gums and skin). They have deleterious effects on the whole body with a high mortality rate (up to 67%). Affected adult cats appear to suffer from more severe clinical signs compared with affected kittens. Many of the cats with this condition had been fully vaccinated. Further investigations into these strains are currently ongoing.
bacterial infection has become recognised as a problem in
cats only recently. Although well known in other species,
until 10 years ago it was not really reported in the general
cat population. In breeding colonies, in combination with
FHV and/or FCV, it can cause fatal pneumonia, with death of
entire litters within hours or days. On its own (in experimental
studies) this bacterium usually causes a mild nasal discharge
and perhaps a slight cough. In experimental studies there
also appears to be a carrier state, and queens have been shown
to shed bordetella in the post-kittening period. The role
of bordetella in cat flu is still being investigated and several
studies on this bacterium are in progress. It is now possible
for researchers to 'type' different strains and what makes
some strains cause disease is an area under active study.
Using this strain typing system, it has also been shown that
this bacterium has, in a small number of cases, been transmitted
from dogs (in which it causes kennel cough) to cats.
typical questions about flu from breeders are shown below.
In all cases, it is essential to involve your vet if your
cats suffer from an outbreak of flu. Your vet may want to
speak to one of the veterinary schools for advice with each
individual disease problem.
my cats catch flu at a cat show?
the answer is probably yes. In a 1994 survey of cats at several
shows in the UK, between 20 and 30% of the cats present were
found to be shedding FCV and about 1% were shedding FHV. It
is notable that these cats were all apparently healthy and
had passed vetting in. Though disinfectants are used between
cats it is certainly possible that transmission could occur
at shows from coats or other equipment used by vets, judges
or stewards, not to mention the risk from the public touching
cats. It must also be borne in mind that going to shows constitutes
a 'stress' and that many FHV carriers would be expected to
shed FHV following a stress - in some cases with signs of
disease. So a cat that gets flu after a show may not have
picked it up there - the stress of going to the show could
have caused the reappearance of the disease.
have had flu in several litters. How can I find out which
infection is present?
you have a problem with cat flu in a breeding cattery, then
your vet may have a suspicion of which infection is present
on the symptoms your cat/kittens are showing, but you will
probably need to do some tests to be sure. In order to look
for the viruses, your vet needs to take a mouth or eye swab. Depending on the test required the swab will have to be placed in special medium supplied by the laboratory (virus isolation) or can be submitted as a dry swab (PCR). A second swab has to be taken and placed in different medium to look
for Bordetella species. These tests can only be done at specialist
laboratories, often the university veterinary schools working
on these infections.
have had flu in my cattery and FHV has been found. What should
diagnosis of FHV infection in a breeding cattery can be very
serious. If found in kittens, they have presumably caught
it from other cats in the household, suggesting the household
has at least one carrier cat. Though the queen is the number
one suspect it is very important to remember that with FHV
cats shed only intermittently - so 'negative' cats in the
household may still be carriers, they just don't happen to
be shedding at that time. Infected queens tend to infect every
litter of kittens born to them, often while they are quite
young. Depending upon the age at which the kittens become
infected they may or may not become ill. Sometimes, the immunity
passed from the queen in her milk protects the kittens from
clinical signs but still allows them to be infected and become
carriers. At other times the infection causes severe disease
in the kittens. If the queen produces successive litters of
badly affected kittens, unless she is extremely valuable to
the gene pool the best advice is usually to neuter and rehome
her - the only other alternative is to isolate, early wean
and hand rear the kittens.
of my cats has a positive swab for FCV. What should I do?
is very common in the breeding cat population. As many strains
are present, the best course of action rather depends upon
individual circumstances. If, for example, many litters of
kittens get severe signs of flu, then the best course of action
will usually be to stop breeding and to wait a few months
before testing the cats again. This approach may allow the
detection of carrier cats and their removal or continued isolation
from the rest of the cattery.
my last litter of kittens, two have died and Bordetella species
was found at post mortem examination. What should I do now?
bordetella is a bacterium, the infection can be treated with
antibiotics. It is best to test the specific strain isolated
from individual catteries to judge which antibiotic it is
best to use. It is not known whether the use of antibiotics
will prevent cats from becoming carriers, as this research
has not yet been done. In other species it can be difficult
to eliminate the infection from individual animals, though
the signs of disease can often be controlled.
my cats are vaccinated correctly. Why have I got flu
in my cattery?
available vaccines do a very good job of preventing disease
due to FCV and FHV, both in the general population and in
catteries. However, no vaccine is 100% effective all the
time in every animal. Factors involved in this include:
- Strain variation: some strains
appear to be more virulent than others, causing more severe
disease and may be able to 'break through' vaccine induced
immunity. Particularly with FCV, the current vaccines do
not protect against all strains, so disease is still possible
even in vaccinated cats.
- Young, susceptible kittens are
born into or brought into the breeding household, where
there are often a large number of cats that may be carriers.
The presence of carrier cats is particularly important -
these cats can infect kittens before they are usually considered
old enough to be vaccinated. In special circumstances it
is possible to vaccinate kittens at a younger age, but this
must be discussed carefully with your vet.
- Vaccinated cats, though usually
protected against the disease, can still become infected
and can become carriers.
- There is now an intranasal vaccine
available in the UK with good efficacy against bordetella.
you are vaccinating correctly and still have a problem, you
should discuss this with your vet. It is usually possible
to investigate such problems, sometimes in conjunction with
the drug company that produces the vaccine, which can be helpful
in producing a plan for control.
I take any special hygiene precautions?
up of infection can occur in the household, especially where
cats are kept in an area that cannot be adequately disinfected.
Feline herpesvirus is a relatively fragile virus and does
not remain infectious for very long in the environment (about
48 hours) but FCV can remain infectious for up to 10 days
in good conditions. Use of a suitable disinfectant is essential,
as is sensible stock management.
I change my management procedures?
of the factors involved in flu is keeping a lot of cats together.
The more cats you have, the more likely one will be a carrier
and will infect the others. Therefore, it is usually best
to try to keep cats in smaller groups. This is usually only
possible where cats have separate accommodation in outdoor
pens or an indoor cattery. Isolation of two or three cats
in back bedrooms or other areas of the house is frequently
not successful, as isolation is hard to maintain. Strict hygiene
is important to prevent cross infection from other groups.
Management of an outbreak will usually involve isolation,
treatment, vaccination and a period of testing, during which
no kittens should be bred, in an attempt to control the disease.
It may be necessary to consider neutering and rehoming. Individual
catteries vary so much it is essential to consult your vet
to produce management procedures that you can work with. In
some cases this is not possible, and a certain level of disease
has to be expected.
Updated November 2008