Titre Testing in Dogs
A titre test is a blood test used to detect antibodies against particular infectious diseases.
In dogs, testing is most useful for the three core viral diseases: canine distemper virus, canine adenovirus and canine parvovirus.
Titre testing can help confirm that a puppy responded to vaccination and can help owners and veterinary surgeons avoid unnecessary core revaccination in adult dogs.
Which Diseases Are Tested?
Core canine titre testing commonly checks antibodies to:
- Canine distemper virus (CDV)
- Canine adenovirus (CAV), associated with infectious canine hepatitis
- Canine parvovirus (CPV)
Tests such as VacciCheck provide a separate result for each of these diseases. Laboratory-based tests are also available.
Humoral and Cellular Immunity
The immune system has different but connected components. Circulating antibodies form part of the humoral immune response, while memory B cells and T cells contribute to longer-term immune memory.
A titre test measures antibodies circulating in the blood at the time the sample is taken. It does not directly measure every part of immune memory or cell-mediated immunity.
This is important because the absence of detectable circulating antibodies does not automatically prove that all previous immunity has disappeared.
What Does a Positive Result Mean?
For canine distemper, adenovirus and parvovirus, a positive antibody result is accepted as evidence that the dog is protected.
A positive result generally means that another core vaccination is not required at that time.
The precise numerical score is normally less important than whether the test confirms the presence of antibodies at or above its recognised threshold.
What Does a Negative Result Mean?
A negative titre does not automatically mean that immunity has been lost. It means that the test has not detected sufficient circulating antibodies at that particular time.
Antibody levels may decline when the immune system has not recently been challenged by the relevant virus. The dog may still retain memory B cells, T cells and other immune memory capable of responding following exposure.
A standard titre test cannot directly measure that cellular memory. It therefore provides only part of the overall picture.
Equally, a negative result cannot prove that the dog remains protected. The dog may have immune memory, may have failed to respond adequately to a previous vaccination, or may genuinely be susceptible.
The result should therefore be interpreted alongside the dog’s age, health, vaccination history, previous titre results and individual risk of exposure.
Immune Memory
The purpose of immune memory is to recognise a previously encountered infectious agent and respond more rapidly if it is seen again.
The body does not necessarily need to maintain the highest possible level of every antibody indefinitely. Antibody levels can reduce over time while elements of immune memory remain.
This is why a falling or negative titre should not automatically be described as proof that all immunity has disappeared. However, because the test cannot demonstrate the remaining memory response, protection cannot be guaranteed from a negative result alone.
The Fire-Engine Analogy
The humoral immune response can be compared with a fire engine. The fire engine waits at the station until it is needed rather than constantly driving around looking for a fire.
In a similar way, the immune system does not necessarily keep every antibody circulating at a high level indefinitely. Memory cells may remain ready to respond if the relevant threat is encountered again.
This analogy helps explain why a low or negative titre is not automatically proof that all immunity has been lost. However, it cannot prove that sufficient protective immune memory remains in every individual dog.
With thanks to Paul Seamons of Messano Golden Retrievers for allowing the original article to be reproduced.
Titre Testing Puppies
One of the most useful applications of titre testing is to confirm that a puppy has responded to its initial core vaccinations.
Current WSAVA guidance supports serological testing from approximately 20 weeks of age. Testing at this stage helps avoid confusing vaccine-produced antibodies with temporary maternal antibodies.
A positive result for distemper, adenovirus and parvovirus confirms active immune protection.
If a puppy tests negative, possible explanations include interference from maternal antibodies, failure of the vaccine to produce an adequate response, a testing limitation or the puppy being a low or non-responder.
The result and available options should be discussed with the veterinary surgeon responsible for the puppy.
Maternal Antibodies
Puppies receive temporary antibodies through their mother’s first milk, known as colostrum. These maternal antibodies help protect the puppy during early life but may also interfere with vaccination.
The level and duration of maternal antibodies vary considerably between puppies. This is why an injection given at six or eight weeks cannot be assumed to have immunised every puppy.
Current guidance recommends a series of core vaccinations with the final puppy dose given at 16 weeks of age or older. Titre testing afterwards can be used to determine whether detectable antibodies have been produced.
Limitations of Titre Testing
- It measures circulating antibodies rather than every part of the immune response.
- It does not directly measure memory B cells or cell-mediated immunity.
- A positive result is much clearer to interpret than a negative result.
- It does not predict protection reliably for every infectious disease.
- It does not replace legally required rabies vaccination for travel.
- It cannot be used in the same way to establish long-term protection against leptospirosis.
Leptospirosis
VacciCheck tests for distemper, adenovirus and parvovirus. It does not test for leptospirosis.
Antibody testing for leptospirosis is not considered a reliable alternative to vaccination because antibody levels do not correspond with protection in the same way as they do for the three core viral diseases.
Whether a dog requires leptospirosis vaccination should be based upon individual exposure risk, local disease information and discussion with the veterinary surgeon.
Veterinary Practices Offering VacciCheck
The map below shows veterinary practices reported to offer VacciCheck. Contact the practice before travelling, as services and availability may change.
Further Information
WSAVA 2024 Vaccination Guidelines
This information is not intended to replace veterinary care. Titre-test results should be considered alongside the dog’s age, health, vaccination history and individual circumstances.