Vaccination of Companion Animals
Animals, just like humans, suffer from a range of infectious diseases.
As veterinary medicine has advanced, prevention of disease has become a priority. One of
the best means of prevention is by creating immunity in the animal. This is usually
achieved by vaccination.
By the turn of the millennium, the principle of vaccination had been
established for over 200 years. Since those early days, enormous strides have been made in the
development of vaccines which have helped to prevent and in some cases eliminate disease
in humans, farm animals and the family pet.
Vaccination also reduces the amount of pharmaceutical treatments (such
as antibiotics) used to control established diseases and, in many instances, has prevented
long term suffering and death. Examples of diseases which can be prevented by vaccination
are shown in the table below.
||DISEASES CONTROLLED BY VACCINES
||Distemper, infectious canine hepatitis, leptospirosis, parvovirus, kennel cough (Bordetella
bronchiseptica and canine parainfluenza virus). Also rabies for
dogs going abroad as part of the PETS
||Feline infectious enteritis (or panleucopenia), feline leukaemia, chlamydia, cat 'flu'
(feline herpes virus and feline calicivirus). Also rabies for cats
going abroad as part of the
||Equine herpes virus 1, influenza, tetanus, viral arteritis. Also rabies (not routinely
used in the UK)
||Myxomatosis, viral haemorrhagic disease
||Paramyxovirus, pigeon pox
Many of these diseases, except rabies, are endemic in the UK. Many of them
are killers, even with veterinary treatment. All of them cause suffering to animals - not
just when the animal contracts the disease initially: damage can often be permanent. Their
manifestation is being suppressed by responsible pet owners who have their animals
vaccinated regularly against disease. This has the effect of reducing the
overall level of disease within the United Kingdom. Incidence of disease varies around the country and
unvaccinated animals introduced to a new area are particularly vulnerable to infection.
It is possible for immunity to develop in an unvaccinated
animal but, for this to happen, the animal must first encounter the disease
and then survive the encounter. With potentially life-threatening diseases,
this is not a serious option as it could result in the death of the animal.
Young animals receive some immunity from their mothers before and
shortly after birth, both via the placenta and, principally, in the first milk (known as
colostrum). It is important the new-borns suck early because Maternally Derived Antibodies
(MDA) are highest in the colostrum at the time of birth. This "natural" maternal
immunity provides disease resistance for some weeks, but is unreliable as there are
variations of MDA levels even within a litter. Because this immunity is not actively produced by the young animal, it
declines over time. Research has been carried out by blood testing dogs and cats to help
establish the timing of MDA decay for various diseases. This provides a guide to the
typical age at which puppies and kittens are no longer protected by the
mother's immunity and indicates the best time to start vaccination.
The first vaccination ("Primary Course")
Vaccines stimulate the body to produce its own defence against
infection, taking over the mother's role in providing protection. In general, puppies and
kittens do not leave their mother until they are eight to nine weeks old, so this is
usually when they receive their first vaccination.
The first vaccination course (for dogs and cats) always consists of two
or more vaccinations. This is because timing for effective vaccination varies between
individuals because of variable Maternally Derived Antibody (MDA) levels and because some vaccines, such as
Leptospirosis, need to be administered twice to achieve a satisfactory level of immunity.
The need for regular boosters
Just as Maternally Derived Antibody (MDA)
declines, so too does the protection provided by vaccination. The animal's
active immunity may be "topped up" as follows.
The Council of the British Small Animal Veterinary Association
considers that it is good practice and good preventative medicine to remind 'bona fide'
clients when booster vaccinations are required.
A long safety record
Whether for disease prevention or treatment, the veterinarian,
the animal owner and the public all have a right to expect that the preparation of animal
medicines is reliably based on the triple standards of quality, safety and efficacy. The
extremely stringent requirements for product registration reflect this. If these
requirements are not met, a vaccine will not be allowed on the market. There are
established procedures for reporting any suspected adverse reactions. Careful monitoring
and review of products and disease patterns ensure that once on the market, vaccines
remain safe and effective.
The benefits of vaccination have been supported by the
working group set up by the independent Veterinary Products Committee to look
at canine and feline vaccination. In their 2001
report (1) they concluded that "vaccination plays a very valuable role in
the prevention and control of the major infectious diseases in cats and
dogs". Although adverse reactions to vaccination, including lack of
efficacy, occasionally occur, the working group concluded that "the
overall risk/benefit analysis strongly supports their continued use".
Moreover, an independent and scientifically peer reviewed study carried out
by the Animal Health Trust at Newmarket has produced the clearest evidence
yet that routine vaccination of dogs in the UK does not increase frequency
of illness (2).
Today's vaccines are very effective and have a remarkably high safety
record. Millions of doses are used annually in the UK alone. The use of vaccines has
brought about levels of disease control against, for example, the killer disease Canine
Parvovirus, that would have been almost undreamed of little more than a decade ago.
Because the incidence of these diseases has fallen as a direct result
of the widespread use of effective vaccines, the chances of an adult pet encountering them
have also reduced. This puts the unvaccinated or un-boosted pet in danger - if it has not
met all the diseases on a regular basis, it may be unprotected.
Sooner or later an
encounter with a massive disease challenge could prove fatal.
(1) Veterinary Products Committee (VPC) Woking Group
on Canine and Feline Vaccination; final report to the VPC published by
DEFRA, May 2001
(2) Vaccination and ill-health in
dogs: a lack of temporal association and evidence of equivalence; D S
Edwards, W E Henley, E R Ely and J L N Wood, Vaccine Journal, Volume
22/25-26 September 2004