Vaccination against canine parvovirus (CPV) is universally recommended by Veterinary Surgeons. CPV is considered one of the “core” (essential) vaccinations for dogs. As such, the WSAVA (World Small Animal Veterinary Association), who publish extensive vaccination guidelines, advise that all dogs, regardless of circumstances or geographical location, should receive a parvovirus vaccination. Other core vaccinations include distemper virus (CDV) and adenovirus (CAV). But why?
Table of contents
- What is parvovirus?
- Which dogs are at greatest risk?
- When are dogs vaccinated?
- Does vaccination need to continue in later life?
- And what about titre testing?
What is parvovirus?
Canine parvovirus is a life-threatening disease with a global distribution, caused by the canine parvovirus type 2 (CPV-2) virus.
The virus is highly infectious and easily carried by “fomites” (objects or materials that are likely to transmit infection). Highly resistant in the environment, the virus withstands extremes of heat, cold and drought and furthermore, is resistant to many cleaning products. As a result, it can survive for many months in the environment in our climate.
CPV disease remains prevalent within the dog population. Even in developed countries, focal outbreaks of disease occur. When a sporadic surge of disease arises, the virus has a tropism (attraction) to rapidly dividing cells within the dog’s body. As such, the gastrointestinal tract and bone marrow / immune system are targeted.
Severe vomiting and diarrhoea, often with immunosuppression and potentially sepsis, are features of the disease. Mortality rates are high with only approximately 50% of puppies surviving, even with supportive, intensive veterinary treatment. The virus can also damage the hearts of very young puppies and cause lifelong cardiac problems.
Which dogs are at greatest risk?
Whilst puppies are at greatest risk, all dogs may catch the disease. Infection occurs through exposure to infected dogs, their faeces, or from objects/areas contaminated with their faeces. Research shows that certain breeds, such as Rottweilers and German Shepherd Dogs may be at increased risk. We suspect that this relates to their genetics.
Puppies when young, will typically passively receive antibodies from their mother, for example in milk. These “maternally derived antibodies” (MDA) will wane within a matter of weeks however and pups must be vaccinated to continue protection against the disease. Levels of MDA will vary significantly between litters and pups and so multiples of vaccines are usually given; with a follow-up booster 6-12 months later.
Vaccination not only serves to protect the individual dog but provides optimum “herd immunity” within the dog population. This then minimizes the likelihood of an infectious disease outbreak.
When are dogs vaccinated?
Puppies can start their parvovirus vaccinations from 6 weeks of age. However, whilst this might be done in a high-risk area / situation, typically a vaccination course would start at 8weeks of age. A further one or two vaccines are given over the next 4-6 weeks. A booster vaccine is administered at 1year of age, thereafter, on a triennial basis (every 3 years).
Does vaccination need to continue in later life?
For parvovirus, yes, vaccination should continue throughout the dog’s life. For most UK vaccine products, once the initial puppy course and a year 1 booster are complete, vaccination for parvovirus is advised once every 3 years. Vaccines should not be given needlessly however, so given that the duration of immunity (DOI) following a parvovirus vaccination may last many years, clients may rightly question why we repeat it every three.
As a rule of thumb, we Vets wish more individual animals to receive vaccinations (thus improving herd immunity); but simultaneously, to vaccinate each individual animal less frequently and only as necessary. Whilst the 3 year period of immunity is considered a minimum following parvovirus vaccination, we adhere to it for many reasons.
Firstly, we all remember individual parvovirus cases that we have lost, despite our best efforts. Vaccination aims to prevent highly infectious disease with high mortality, and hence our recommendations for them. This applies to both puppies and adult dogs alike.
Secondly, very occasionally, a dog will be a “non-responder” and not adequately produce a protective level of antibodies following a vaccination. Repeated vaccination, “scoops up” these previous non responders and ensures they are latterly safeguarded.
Thirdly, when a parvo outbreak happens within a finite area, transmission happens fast and with no warning or clue. Your dog needs to be protected before this occurs to ensure that they remain safe. Administering a vaccination at the time of a local parvo outbreak still risks your dog falling ill, since it will take at least a week for protective antibodies levels to peak.
And what about titre testing?
You may have heard about antibody (titre) testing for dogs. These blood samples look at levels of antibodies within an individual dog and help determine the DOI after vaccination (core vaccines). They act as a guide to indicate whether a dog has adequate protection against a disease. If titres are high, protection is considered appropriate and vaccination can be postponed. If titres have declined however (and the animal is considered vulnerable to infection), re-vaccination is advised. Whilst this theory is fine “on paper” it must be remembered that there may be some limitations with the practical application of these tests.
In immunology, there are 2 broad types of immunity.
The humoral (in which antibodies are induced) and the cell mediated. Titre tests will only document the antibody type of protection and as such, this may lack correlation with total protection. Titre testing may therefore, not be fully representative of the entire body wide immunity.
Secondly, it can be very hard to predict when titre levels will start to fall.
By only testing this once a year, there exists a small risk that your dog is left open to infectious disease in the interim 364 days. Titre tests need to be regularly repeated to ensure adequate protection.
Thirdly, and as more of an aside, titre testing is expensive.
Typically, laboratory tests often exceed the cost of the vaccination itself. It is only available for the core vaccinations since there exists a clear lack of correlation with it and protection for diseases such as Leptospirosis and canine parainfluenza.
We should remember though, that titre testing can be useful however in certain individuals. Those dogs who are on immunosuppressive medication, have immunosuppressive diseases or who rarely, are considered to have had a possible previous reaction or adverse event following vaccination. As ever, a patient-specific consultation and tailored advice should be given, adjusted and directed to the particular needs of your dog. The need for continued adequate parvovirus protection comes about not only through the aggressive nature of the disease itself, but also as a direct result of potential fomite and environmental transmission of the virus.
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