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Cats and vaccines

Cats and vaccines; what are we preventing?


Cats, our beloved feline friends, are susceptible to many viruses which cause severe disease and even death. Thankfully, we are able to vaccinate against many of these diseases, and do so regularly. Vaccines work by modifying a virus which usually causes disease, so that it can no longer cause illness, but will still stimulate the immune system to mount a response to protect the body. This means that when Felix is enjoying his nightly stroll, if he comes into contact with a deadly virus, such as feline parvovirus, his immune system will have a memory of encountering the virus (from the vaccine), and mount an attack on it to prevent infection.

Vaccines can be described as core and non-core. Let us have a look at the core and non-core vaccines, and go into detail about the viruses to see the importance of prevention.


  1. Which vaccines should my cat be receiving?

Core vaccines: Cats are commonly vaccinated against feline parvovirus (the cause of feline infectious enteritis), herpes virus and calicivirus. Protection against these three viruses are known as “core vaccines”; the World Small Animal Veterinary Association advises that cats should receive their first vaccines at around 9 weeks, followed by a second at 12 weeks, and then annually. Some cats, such as those who live in a single-cat household, do not go into catteries and live exclusively indoors, may require vaccination less frequently.

Non-core vaccines: rabies vaccines and feline leukaemia vaccines are considered non-core vaccines; not every cat will need vaccinated every year, but they do need protection appropriate to their lifestyle. Also included in non-core vaccines are the bacterial agents involved in cat flu – Bordetella bronchiseptica and Chlamydophila felis.


  1. The viruses; why you should vaccinate to protect your cat


  1. Feline Infectious Enteritis/ Feline Panleucopenia Virus

The basics: this virus is often fatal, and spreads rapidly between cats. It is known as feline infectious enteritis (FIE), or feline panleukopenia virus.

What is it, and how is it spread? FIE is caused by a parvovirus. It is spread by faeco-oral transmission and survives well in the environment. Infected cats can shed the virus for 6 weeks after infection – this means it can spread extensively in multi-cat households, catteries or communities with many outdoor cats who are in contact, if they are not vaccinated.

What are the risks?

  • Gastroenteritis; cats have an inflammation of their stomach and intestines, and can have vomit and diarrhoea with blood in it. This can cause severe electrolyte disturbances and dehydration, and can kill cats. Kittens are at a particular risk of death.
  • Panleucopenia; this term describes a drop in white blood cells, the immune defence cells of the body. The virus can replicate in bone marrow and lymph nodes, which disrupts the production of these essential defences of the body, the white blood cells. Cats are therefore unwell and susceptible to other infections.
  • Cerebellar hypoplasia; this is a condition where a part of the brain, the cerebellum, which coordinates movement, is underdeveloped. This only happens when a pregnant cat is infected during her pregnancy; her kittens can be born with this condition.

Special Note: The FIE vaccine is the only one that doesn’t need to be repeated annually for reliable protection! It last a minimum of 3 years, so most cats won’t need it every year.


  1. Feline Herpes Virus (FHV)

The basics: this virus is spread between cats by saliva and discharge from the nose. The virus infects cats for life.

What is it, and how does it spread? Herpes virus is a DNA virus; it is spread in ocular, nasal and oral secretions, causing infection of the upper respiratory tract and conjunctiva. Signs will appear around 1 week after infection, and damage to the tissues of the upper respiratory tract can then allow for secondary bacterial infections. It is rare for it to spread by environmental contact, however, this can occur in multi-cat households.

What are the risks? Infection can cause disease and carrier states.

  • Carrier states; the virus can hide out in nerves, and the cat has no signs of disease. However, stress (such as moving house), pregnancy and the administration of steroids can cause the disease to recrudesce (flare up again); this means they can shed the virus and infect other cats, and the cat itself may have a recrudescence of clinical signs and be sick.
  • Disease; around 1 week after infection, the cat will suffer from severe upper respiratory tract disease, which can be fatal to kittens and elderly cats. Common signs of infection are:‚Äč Sneezing, Ocular signs; conjunctivitis and discharge from the eyes, which often results in crusting around the eyelids, eye ulcers and eye pain (squinting, or “blepharospasm”), Excessive drooling and A fever (pyrexia)


  1. Feline calicivirus

The basics: This virus spreads by direct contact or through air-borne virus particles and shared contact with the environment.

What is it, and how does it spread? Calicivirus is an RNA virus; it has better environmental persistence than FHV, meaning that cats who share the same environment are at higher risk of becoming infected. Transmission can be by direct contact with infected cats who may or may not be showing signs, or by environmental spread, although it is more likely to infect cats who have direct contact with infected fellow felines.

What are the risks? Like FHV, cats can become carriers, although unlike herpes it isn’t usually for life. They tend to also show signs around 1 week after infection.

  • Carrier states; like FHV, the disease can remain in the cat’s body and not show any signs or be spread until a period of stress.
  • Disease; severity of disease is highly variable as there are many variations of the virus (think of it as members of the same family who all have different personalities!) Clinical signs include: Oral ulcerationA feverDepression and dullnessLimping; this is a less commonly seen effect of FCV, but it can cause a “polyarthritis”, and these painful joints can cause transient limping syndrome and Respiratory signs and conjunctivitis; like FHV, FCV can infect the upper respiratory tract, but usually causes less severe ocular discharge and difficulties breathing.


What is cat flu?

Cat flu is actually caused by a group of viruses and bacteria working together; it is generally characterised by FCV and FHV causing damage to the upper respiratory tract, which allows for bacteria, which usually do not cause disease by themselves, to infect poor Felix’s damaged tissues. It makes cats very dull, have difficulties breathing and go off their food, which makes them feel even worse! It is therefore important to vaccinate your cat annually if he is in a high-risk group (a cat who regularly goes outdoors, a member of a multi-cat household or has immunosuppression), or every 3 years if a very low-risk cat (indoor only with no other cats and does not spend time in catteries).


Please speak with your vet about formulating a plan to protect your cat from these viruses; they cause severe welfare implications, and are often fatal. Vaccines are tested for efficacy and safety; vets only have your cat’s welfare and your peace of mind at heart, and are happy to discuss the importance of vaccination at any time.

“In ancient times cats were worshipped as gods; they have not forgotten this.” - Terry Pratchett