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Keeping your pet healthy: vaccinations

4th May 2017

Most of us don’t think anything of booking our pets in for their ‘jabs’.  But have you ever wanted more information about what those jabs are for? Here, we give a comprehensive guide to the vaccinations available at Orchard Vets, and the diseases they prevent.

 

What is a vaccination?

It was known for many years before the development of vaccinations, that people (and animals) that had survived and recovered from certain infectious diseases, such as smallpox, were unable to catch the infection subsequently. This is due to the unique capabilities of the immune system to develop what is called an ‘adaptive response’.

When a pathogen (a bacterial, viral or fungal infectious agent) first enters the body, it is recognised by the immune system as a danger.  The immune system – particularly the white blood cells – responds to this infection with a variety of measures to attack the pathogen.  This helps fight off the disease, and the body eventually recovers.  However, this doesn’t take place quickly enough to prevent clinical signs of the disease, and damage to the body.

After the infection, a subset of white blood cells known as memory cells are left behind. These cells are primed to recognise the infection a second time.  If the pathogen enters the body again, the memory cells quickly swing into action, and the pathogen is attacked and neutralised before it causes damage.  However, not every person or animal that suffers an infectious disease – especially serious ones such as smallpox or polio in people, or parvovirus in dogs – will survive.  A means was needed to try to trigger the protective immune response without causing illness.

This is exactly how a vaccination works.  A small quantity of the antigen (a protein on the surface of a foreign cell) is administered –   but having removed the ability of the pathogen to attack the body and do harm.  This ‘teaches’ the immune system to recognise the natural pathogen well enough to respond quickly to an infection.  The pathogen may be rendered harmless in a number of ways:

  • By killing it (inactivated vaccine)
  • By modifying it, so it is weaker and not able to cause disease (modified live vaccination or attenuated vaccine)
  • By removing a small amount of the pathogen’s genetic material and placing it in a harmless substitute (subunit vaccine or vectored vaccine)
  • In some cases, it is not the pathogen itself, but a toxin it produces which is injected in a weakened or inactivated form (toxoid) – tetanus vaccination is an example of this.

Generally, modified live vaccinations and some of the vectored vaccines produce the best immunity against disease.  Unfortunately, not all pathogens are suitable for producing a modified live vaccination.  In addition, MLVs cannot be given to animals with a weakened immune system, or there is a risk that they will be able to cause illness, even in their attenuated state.  The cannot be given to pregnant animals, as they can cause problems in the unborn young.  In most of these cases, inactivated vaccines are safe, and may be a suitable alternative.

 

What vaccinations should my pet receive?

Just like in people, there are a large number of vaccinations available for pet animals, and also in livestock. Some vaccinations should be given to all animals of a particular species, worldwide.  These vaccinations are referred to as ‘core vaccinations’.  A ‘non-core’ vaccine is generally one against disease that is either less common, less serious, or possibly not present everywhere.  A vaccine that is considered ‘non-core’ in an area where a disease is not present may be considered a core vaccine in an area where the disease is common.

The exact vaccines we recommend for your pets may vary depending on their lifestyle, or any travel that is intended.

 

Dogs

 

Distemper, hepatitis and parvovirus

One of the components of our vaccination schedule for dogs is called ‘DHP’ which stands for ‘distemper, hepatitis and parvovirus’. This is considered a core vaccine by the WSAVA (World Small Animal Veterinary Association) – they recommend that every dog receives vaccinations against these diseases.

Distemper, which was sometimes known in the past as ‘hard-pad’ is a viral disease affecting dogs and a variety of related species, as well as seals and some primates.  It presents with fever, discharge from the eyes and nose, and laboured breathing, as well as hardening of the nose and footpads.  In dogs which survive the acute phase, serious neurological signs often develop.  In many cases, these continue to worsen, and the dog often has to be euthanased or face a lifetime of pain and suffering.   The mortality rate of distemper is around 50%.

Luckily, thanks to widespread vaccination, distemper is rarely seen in the UK, but it remains prevalent in some other countries. In Finland in 1995, the combination of an ineffective batch of vaccine and a previous drop in the proportion of the population that was vaccinated led to a significant outbreak of distemper.  This clearly shows that the disease remains a serious threat even in populations previously free of the disease.

Infectious canine hepatitis is the name given to disease caused by canine adenovirus type 1 (CAV-1), to which young puppies are most vulnerable.  The infection leads to liver disease or even liver failure, bleeding disorders as well as respiratory signs and corneal oedema (a cloudy or blue appearance to the normally clear surface of the eye).  This disease can be fatal, though it generally carries a lower mortality rate than other infections.  Similar to distemper, we are lucky that cases of ICH are rarely seen nowadays thanks to a good uptake of vaccination in the dog population.

Canine parvovirus, often just called ‘parvo’, is the third component of the DHP vaccine, and the one most commonly still seen in the UK.  This is due to its extremely infectious nature, and the fact that the virus can remain viable in the environment for a significant length of time – over 10 years in the soil.

‘Parvo’ causes a severe enteritis – infection of the lining of the gut. Affected animals present with lethargy and vomiting in the early stages, progressing to a profuse bloody diarrhoea.  The damage caused by parvovirus is very deep and severe compared to other pathogens that affect the gut;  blood and proteins are lost through the damaged gut as well as fluid, which severely debilitates the dog.  In addition, the virus also lowers the dog’s white blood cell count, leaving them less able to fight off the virus, and any other bacteria entering through the damaged gut.  Without treatment, the mortality rate from parvovirus is over 90%, and even with intensive supportive hospital treatment, up to half of affected dogs will not survive.  Given that many of the cases are young puppies, this is particularly heart-breaking.

 

Leptospirosis

Leptospirosis, or ‘lepto’ is the name given to disease caused by bacteria of the species Leptospira. This is a large group of bacteria, only some of which are associated with disease.  Some species of animals – including rodents, pigs and cattle – can carry leptospirosis with little or no signs of disease themselves, but pass the disease on to humans or other animals.  In some places, leptospirosis is not a significant risk to dogs, so the vaccine is described as ‘non-core’ by the WSAVA (that is, not every dog worldwide would benefit from vaccination).  The bacteria survives well in wet environments that are not too hot and not too cold.  As you can imagine the climate in the UK, especially in Somerset, is perfect for the potential transmission of leptospirosis.  For this reason, in the UK the vaccine is generally considered to be a core part of a protective vaccination strategy.

In the body, leptospira bacteria attack the liver and kidneys, causing jaundice and potentially fatal failure of either organ system. In dogs that recover from the infection, they shed bacteria in their urine for a prolonged period of time.  Leptospirosis is what is known as a zoonotic infection – one that can be passed from animals to humans – so these dogs can represent a significant risk to human health.

The vaccine against leptospirosis that we use at Orchard Vets is a four-strain vaccine, helping to protect dogs against L. Canicola, L. Grippotyphosa, L. Icterohaemorrhagiae and L. Pomona.  We made this switch in 2015 after outbreaks of leptospirosis close to here, caused by strains that were not included in the vaccine we were using before then.

 

Kennel cough

‘Kennel cough’ is the colloquial term given to a condition known more correctly as canine infectious tracheobronchitis.  This is the most common infectious disease among dogs in the UK.  The two main causes are a bacteria known as Bordetella bronchiseptica (distantly related to the bacteria that causes whooping cough in humans) and parainfluenza virus.  Contrary to what the name suggests, kennels are not the only risk.  Anywhere that dogs have close contact – such as training classes, ‘doggy day-care’, or even popular walking or exercising spots can present a risk as the infectious agents can survive in the environment.

The classical clinical sign of kennel cough is a harsh, hacking cough, often ending with the dog gagging or retching.  This is often triggered by pressure on the trachea – such as pulling on the lead.  The dogs may have a fever, in which case they may be depressed, but often are well in themselves.  In some dogs, such as very young dogs, or older dogs that may have a weaker immune system or underlying heart or lung problems, there is a chance a kennel cough can progress to pneumonia and make them very ill.  Coughing can last for several weeks, and an infected dog remains a risk to others for this time.

Kennel cough vaccination is considered a ‘non-core’ vaccine.  Not every dog needs it, but it may be required or recommended depending on their lifestyle.  Most reputable boarding kennels or day-cares will require your dog to be vaccinated, to reduce the risk of an outbreak.  Dogs that mix a lot with other dogs – at classes or shows, or even just those that play with a lot of other dogs on a walk – would also benefit from being protected.

The kennel cough vaccine is unusual in that it is delivered intranasally, rather than by injection.  This gives a faster and stronger immunity against respiratory infections, by triggering the local immune response – exactly the area you want ready to fight an infection.  Similar to a flu vaccine, a kennel cough vaccine cannot guarantee protection against infection, due to the variety of pathogens that may be involved.  However, a vaccinated dog is much less likely to be infected, will be less severely affected if so, and will be less infectious to other dogs.

 

Rabies

Rabies vaccination is only required for pets that are travelling outside the United Kingdom – for example to Europe under the pet passport scheme.  This is because we are lucky enough to be free of rabies in the UK, and we very much want it to stay that way!

Rabies is a viral infection that attacks the central nervous system.  Initial symptoms can include extreme agitation or aggression, hypersalivation, progressing to paralysis and death.  Once contracted, rabies is always fatal, in animals or humans.  An dog infected with rabies represents a serious risk to humans, as anyone they come into contact with is at risk of infection.

Though rabies vaccination is not required for resident dogs in the UK, to obtain a pet passport it is a mandatory requirement.  In many other countries, where there is a risk of dogs contracting rabies from wildlife, and potentially passing it on to humans, rabies vaccination may be a legal requirement for dog ownership.

 

Cats

 

‘Cat flu’

Cat flu is the name given to the complex of clinical signs shown by cats infected with a group of pathogens causing upper respiratory and ocular (eye) signs. These are feline herpes virus (FHV), feline calicivirus (FCV) and the bacteria Chlamydophila felis.

Feline calicivirus causes fever, sneezing and nasal discharge, conjunctivitis and ulcers in the mouth.  In some cases the joints may also be affected, causing lameness.

Infection with feline herpes virus causes very similar clinical signs – sneezing and nasal discharge, conjunctivitis, and often ulceration of the surface of the eye.  Not all of these clinical signs will be present in cats infected with these viruses.

Both of these viral infections can demonstrate a behaviour known as ‘latent infection’.  This is when the infection remains present in the cat’s body after they have recovered.  Periodically they may shed virus again, potentially infecting other animals, and sometimes showing clinical signs again.  This is particularly a feature of FHV.  This can make control difficult.  Vaccines are effective, but if a latently infected mother gives birth to a litter of kittens, the stress of pregnancy and nursing can cause her to start to shed virus again.  Kittens may then become infected before they reach the age at which they can be vaccinated.  However, even these cases benefit from the protection given by the vaccine against the other pathogens to which they have not been exposed.

The cat vaccine we use here for our core vaccination in cats is Nobivac Tricat.  This vaccinates against FHV and FCV.  We do not routinely vaccinate cats against Chlamydophila; the vaccines do not prevent cats becoming infected or shedding the infectious agent, so are not very effective at disease prevention.

 

Feline panleukopaenia virus

The third component of the core cat vaccination is against panleukopaenia virus.  This is closely related to parvovirus in dogs, and causes similar clinical signs of a very severe enteritis.  The virus also causes a very marked reduction in white blood cells that would normally fight infection (the name of the virus essentially means ‘low numbers of all white cells’).  This contributes to the very high mortality in affected cats.  Infection is most likely and most serious in young kittens; it is important that all breeding cats are kept up to date with their vaccinations so they can pass protection on to their litter.

 

Feline leukaemia virus

Feline leukaemia virus (FeLV) does exactly what the name suggests.  Infection can lead to types of leukaemia or cancer of the bone marrow later in life. As you might imagine, if these develop, they are highly fatal.  The clinical signs associated can be very variable, depending on exactly what form the disease takes.  In many cases, the cat may just be lethargic or weak, and blood testing is required to diagnose exactly what is going on.  Infection with FeLV does not usually lead to clinical disease for some time, often several years.  Infection and disease is generally rare in the UK, though it can be locally common – especially in some communities of feral cats, which may the present a risk to pet cats.

Not every cat requires immunisation against FeLV.  The virus is passed on by contact with other cats, particularly prolonged close contact.  Mutual grooming, sharing food and water bowls or sharing litter trays all represent an infection risk. The disease can also be passed on by fighting.  A cat that lives indoors by itself, for example, would have a low risk lifestyle and may not require vaccination.  However, cats that spend time outdoors and may come into contact with other cats, or even indoor-only cats that live in a multicat household (unless every cat has been tested negative for FeLV) might be at risk and vaccination should be considered.

 

Rabies

Just like dogs, cats can be infected with rabies, most commonly through contact with infected wildlife such as bats. Cats resident in the UK do not require rabies vaccination, as we are lucky enough to be free of rabies.  However, cats travelling to mainland Europe under the pet passport scheme require rabies vaccination.

 

Rabbits

Compared to cats and dogs, the pet rabbits we see are less likely to be vaccinated. However, rabbits are at higher risk of contracting a serious infectious disease than dogs or cats.  Also, both diseases that we vaccinate rabbits against are incurable and fatal.  So of all our furry pets, the bunnies are really the ones that need protection the most!

Rabbits are at high risk because we have a large population of wild rabbits.  The two diseases pet rabbits can catch from their wild cousins are myxomatosis and viral haemorrhagic disease.  Both agents have been exploited by humans to control the wild rabbit population, putting pet rabbits at risk.

 

Myxomatosis

Myxomatosis is a viral disease that first reached the UK in the 1950s.  It spread rapidly, due to people (illegally) deliberately introducing sick rabbits into burrows.  The aim of this was to spread the infection to control the wild rabbit population.

Affected rabbits have swollen, watery eyes and nostrils, and also swelling around their genitals.  They are blind, and often more likely to be taken by predators.  The infection also spreads to their lungs.  Affected rabbits die 2 days to 2 weeks after the onset of clinical signs.  There is currently no effective treatment, and affected rabbits are euthanased to prevent further suffering.

The virus can be spread by biting insects such as rabbit fleas or mosquitoes; direct contact with infected wild rabbits is not required for a pet rabbit to acquire the infection.

 

Viral haemorrhagic disease

Viral haemorrhagic disease, or rabbit haemorrhagic disease first emerged in the early 1980s, originally in China, and spread rapidly worldwide.   The virus is spread by direct contact with infected animals, mainly by respiratory secretions.  However, it can be carried short distances on the wind; very close contact with a wild rabbit is not needed for infection to occur.

As the name suggests, the disease interferes with normal blood clotting mechanisms in the body.  Clots form in the large blood vessels, especially of the heart and lungs, leading to rapid death.  Affected animals are unfortunately usually found dead in their hutch, sometimes with a bloody discharge from the nose but often with no other signs.  As with myxomatosis, there is no effective treatment, so protection by vaccination is vital.

There are now two strains of VHD virus in the UK.  The newest only appeared a year or two ago.  Vaccination against both types is recommended, and is offered here at Orchard Vets, alongside myxomatosis vaccination.

 

How many injections does my pet need?

In most cases, young puppies and kittens receive a series of 2-3 vaccinations at intervals of 2-4 weeks, depending on the vaccine.  This is because at a young age, the immunity received from the dam can interfere with the vaccination and prevent a proper immune memory developing.  We don’t know when this will occur in each animal.  We could wait until we know it will have waned in every animal, but that might leave some at risk of infection for a prolonged period of time (especially if their mother’s immunity was weak).  Instead, we start to vaccinate from when immunity might be starting to wane, and continue until we can be sure the animal will mount an immune response.  This leaves the pet vulnerable for the shortest possible time (hopefully hardly any time at all!).

The recommendations for revaccination vary depending on the type of vaccine.  Modified live vaccinations, such as the DHP vaccine or rabies vaccine, induce long-lasting immunity in the pet.  It is not really possible to say how long this will last in each individual animal, so vaccine intervals are usually based on the shortest duration of immunity that was demonstrated, ensuring that protection is unlikely to lapse in any pet.  For this reason, these vaccines are given every three years to maintain protection.

Other vaccines may not provide immunity for as long.  An example of this is the leptospirosis vaccination, which is an inactivated vaccine.  Inactivated vaccines do not trigger immunity as well as a modified live vaccine, but for some pathogens or some patients may be the only vaccines that are available or suitable.  These vaccines need to be administered more frequently (annually, in the case of leptospirosis vaccination) in order to maintain effective immunity.

 

Can I test my pet to find out if they are protected?

The body’s response to certain vaccines can be measured by testing the antibody level in the blood – a process known as titre testing.  For example, under the old pet passport rules, a pet had to have their rabies antibody titre measured to prove that they had mounted an effective response to the vaccination before they could return to the UK.  A positive antibody titre test demonstrates that the pet has a protective immune response against disease.  However, it does not give us any information about when that immunity might start to wane.  This might be any time from just after the test to several years in the future.  It is therefore very difficult to give accurate information about exactly how often titre testing should be carried out.  It would be sensible to consider an annual test to keep checking immunity.

Conversely, does a negative response mean that the pet is not protected? Not necessarily, as having circulating antibodies is not the only aspect of mounting an immune response against disease.  However, only way to know for sure if a pet was protected would be to expose it to the disease and see if it develops signs – not a very practical or ethical way of checking!  As vaccines are very safe and well tolerated, if a pet has a low antibody tire we would generally recommend revaccinating to ensure they are protected.

Unfortunately, for some vaccines, such as the leptospirosis vaccination or kennel cough vaccination, titre tests are not useful.  In these cases periodic revaccination is recommended (usually annually).