Vaccination in Cats

Recent advances in medical science have resulted in an increase in the number and type of vaccines that are available for use in cats.  Cats can be vaccinated against many different diseases. Some common vaccinations are for:

• Feline panleukopenia (= feline infectious enteritis; feline parvovirus)
• Feline herpes virus type 1 (= FHV-1; feline rhinotracheitis virus)
• Feline calicivirus (= FCV)
• Feline chlamydial infection
• Feline leukaemia virus (= FeLV)
• Feline immunodeficiency virus infection (FIV)
• Bordetella infection
• Rabies

Attempts are being made to produce vaccines against other infectious diseases in cats, some are already available in other countries e.g. an intranasal vaccine against feline infectious peritonitis (FIP).

How do vaccines work?

Vaccines work by exposing the body's immune system to a particular infectious agent.  This causes the white blood cells to react to fight the infection by producing proteins (antibodies) which are able to bind to and neutralise the infectious agent (antigen).  Antibodies work together with other white blood cells (lymphocytes) which are able to identify and kill cells within the body which have become infected by the agent (cell mediated response).  After vaccinal exposure the body 'remembers' the particular antigens so that when they are encountered again it can mount a very rapid and strong immune response preventing the cat from showing clinical signs of disease.  It is important to realise that most vaccines work by preventing your cat from becoming ill and may not prevent it from becoming infected.  This means that if a vaccinated cat becomes infected it may still shed the disease producing organism which can infect unvaccinated animals which will then become ill.  This is not a major consideration in the pet cat but may be important in the breeding colony.

What is the difference between the various types of vaccine?

Three major types of vaccine are produced for use in cats.

1.  Modified live vaccines- these vaccines contain live organisms that are weakened (attenuated) so that they do not produce disease but will multiply in the cat's body.  Live vaccines are generally considered to cause a stronger, longer lasting immunity than inactivated vaccines.  It is not advisable to use modified live vaccines in pregnant queens or cats whose immune system is not working properly e.g. cats infected by feline immunodeficiency virus (FIV).

2.  Killed (inactivated) vaccines - these vaccines are prepared using fully virulent organisms that have been killed by chemicals, UV light or radiation.  Because, on their own, they do not give such a high level of protection a chemical (adjuvant) is added to the vaccine to stimulate a better immune response.

3.  Subunit vaccines  - these are dead vaccines in which the infectious organism has been broken apart and only certain parts are included in the vaccine.  In some cases this is achieved by using genetic engineering techniques.

When should my kitten be vaccinated?

Generally kittens are vaccinated for the first time at between 8 and 10 weeks and a second dose given at 12 weeks.  A kitten will not be fully protected until 7-10 days after the second vaccination.  Under specific circumstances your veterinarian may advise an alternative regimen.

How often should booster vaccinations be given?

Booster vaccination is generally carried out yearly.  All cats should be boosted regularly, adult cats are also susceptible to these infections particularly as they grow old and their immune system becomes less efficient.

Will vaccination always protect my cat?

Vaccination will protect the vast majority of cats but under some circumstances vaccine breakdowns will occur.  There are many reasons for this including:-

1.  Variations between different strains of viruses - this is particularly true of FCV infection which has a large number of different strains not all of which are covered by the vaccines available.

2.  Maternally derived antibodies - when a kitten is born it is protected in its early life by antibodies passed from the queen in the first milk (colostrum).  These antibodies will also prevent vaccination from working properly. The amount of colostral antibodies that each kitten receives is variable hence the age at which a kitten can be vaccinated will also vary.  This is part of the reason that two injections are given in the primary course.

3.  The cat was not healthy at the time of vaccination - 'stress' can prevent a good response to vaccination.  For this reason it is better to let a kitten settle in its new home for 5-7 days before a vaccination is given.

If you feel your cat has contracted an infection for which it is vaccinated then let your veterinary surgeon know so any tests to try and establish why vaccination has failed to be protective can be undertaken.

What are the risks of vaccination?

Your veterinary surgeon will be able to advise you.

Which are the most important vaccinations to have?

This is a difficult question and will depend on individual circumstances including the area you live in and the lifestyle of your cat.  Your veterinarian will be able to advise you of the most appropriate vaccinations to give your cat.

Feline panleukopenia infection

This is anuncommon disease that causes a severe and often fatal gastroenteritis.  Vaccination provides a high level of long lasting protection.

Feline respiratory virus infection

Disease is caused by FHV-1 or FCV and is commonly termed 'cat flu' whilst not usually very serious it is a common disease in unvaccinated cats and can cause long-term problems.  Vaccination is less effective as immunity is not long lived.  Cats at high risk may needed to be vaccinated twice yearly to provide better protection.

Feline Chlamydial infection

This tends to be a particular problem in colony cats.  Chlamydiosis is a bacterial infection causing a painful inflammation and swelling of the conjunctiva (the membrane around the eye) and has been associated with infertility in queens.  Infection in colonies of cats can last for long periods as protection against reinfection is relatively short lived.  Vaccination can help to prevent infection becoming established in a colony and can be used in conjunction with treatment where infection is already present.

Feline leukaemia virus infection

Whilst the majority of cats are able to combat this infection a significant proportion (about 30%) will become persistently infected by the virus.  The vast majority of persistently infected cats will die from tumours or due to the immunosuppression caused by the virus.  Current vaccines provide a good level of protection and do not interfere with routine testing for the virus in breeding colonies.  Because the virus tends to take many months before it causes disease infected cats can appear completely normal.  For this reason your veterinary surgeon may suggest that your cat has a blood test to make sure it is not infected before vaccination.  Despite vaccination a few cats will still become infected with the virus. 

Feline immunodeficiency virus infection (FIV)

FIV is a common infection of cats in Australia and comes from the same family of viruses as the Human Immunodeficiency Virus (HIV).  Whilst it can be a cause of immunodeficiency in cats (feline AIDS) many cats live for a long period of time, often years before the virus affects their health.  FIV is transmitted by saliva and therefore cat’s being bitten by an infected cat are at risk.  Cats that are kept indoors in a household where there are no infected cats do not need to be vaccinated against FIV.  For cats that go outdoors, FIV vaccination may help reduce the risk of infection.  It is important that you test your cat prior to vaccination as vaccinating an infected cat will not help it.  Once a cat is vaccinated it will become positive on conventional tests for FIV as these tests detect antibodies to the virus.  This is important because currently it is impossible to tell whether your vaccinated cat has FIV once vaccinated – i.e. whether the vaccine was not effective in preventing infection should your cat ever be exposed.  It is also important to have your FIV-vaccinated cat microchipped for identification should it ever go missing – this is because many cat shelters will test for FIV before rehoming unidentified strays.  If your cat is FIV positive they may elect to euthanase your cat thinking it is a stray cat with FIV rather than a vaccinated pet.

REGULAR VACCINATION IS AN IMPORTANT PART OF ROUTINE HEALTH CARE FOR YOUR CAT AND HELPS TO ENSURE YOUR CAT REMAINS FIT AND WELL.