Serological Responses to Canine Vaccination

Why Test?

Serological Screening to Verify Success of Initial Immunization Series

Puppies In A Basket Photo By Judi Neumeyer On Unsplash — Photo by Judi Neumeyer on Unsplash

The American Animal Hospital Association (AAHA) and World Small Animal Veterinary Association (WSAVA) recommend that puppies receive core vaccines, first at six to eight weeks of age, then every two to four weeks until 16 weeks of age or older. This is traditionally followed by a booster, either at 12 months of age or 12 months after completion of the puppy series.

The rationale for the booster is that it will result in a proper adaptive immune response in puppies whose humoral adaptive immune response is still absent or incomplete. Potential reasons listed in the current WSAVA guidelines are residual maternal antibody, inadequate antigenicity of vaccine components or the failure of the animal’s immune system to respond to one or more core vaccines.

A vulnerability of this approach is that it can leave a puppy inadequately protected for an extended period of time if there were an inadequate response to one or more of the components of the puppy shots. The Michigan State University Veterinary Diagnostic Laboratory (MSU VDL) recently tested antibody responses to canine parvovirus-2 (CPV-2), canine adenovirus-2 (CAV-2), and canine distemper virus (CDV) in sera from 50 immunized dogs that were up to 12 months of age. The virus neutralization (VN) test was used to quantitate serum antibody levels to CAV-2 and CDV. The hemagglutination inhibition (HI) test was used for quantitative determination of serum antibody titers to CPV-2. The cut off levels indicative of clinical protection are 32 or higher for CDV, 80 or higher for CPV-2, and 16 or higher for CAV-2.

The data presented in Table 1 indicate that 24% of dogs (12 of 50) had one or more titer(s) below the cut off. The percentages of inadequate titers in these dogs were 4% for CAV-2 and 16% for both CPV-2 and CDV. See Table 1 for specific titers and ages of dogs with inadequate titers and Table 2 for those dogs with adequate post-vaccination titers as comparison.

In Denmark, seroconversion was determined in a population of 135 pups aged between 8 weeks and 12 months. Most of these dogs had finished the early life protocol, were unlikely to have received a dose at 14-16 weeks, and had not yet received a 12 month booster. The percentages of non-responders in this population were 25.3% for CPV-2, 20.7% for CAV-2, and 12.6% for CDV.

Based upon this, it would be reassuring to both owners and veterinarians to verify that a puppy properly responded to the series of three to four core vaccine shots by testing the serum antibody levels four weeks after completion of the “puppy shot” series. This would typically be around 20 weeks of age.

An overview of this approach and the decision making associated with it is presented in the WSAVA’s “Guidelines for the Vaccination of Dogs and Cats.”

Table 1: 12 of 50 Dogs with One or More Titers Considered Inadequate

CAV-2

CPV-2

CDV

Age in Months
128

<10

16

4
64

<10

<8

4
<8

≥640

≥512

7
<8

<10

<8

7
≥512

<10

8

8
≥512

40

<8

9
256

10

128

11
≥512

≥640

16

11
256

≥640

16

11
≥512

<10

≥512

11
≥512

20

128

11
≥512

≥640

<8

11

Table 2: 38 of 50 Dogs with Adequate Titers

CAV-2

CPV-2

CDV

Age in Months
≥512

≥640

≥512

2
≥512

≥640

≥512

3
64

320

≥512

3
256

160

64

4
≥512

≥640

≥512

4
128

≥640

≥512

4
≥512

160

≥512

5
≥512

≥640

≥512

5
≥512

≥640

≥512

5
≥512

≥640

128

5
128

160

32

5
256

≥640

≥512

6
128

320

≥512

7
≥512

320

256

8
256

≥640

≥512

9
≥512

≥640

128

11
≥512

≥640

≥512

11
128

80

32

11
≥512

≥640

≥512

11
256

≥640

≥512

11
≥512

≥640

64

11
≥512

≥640

128

11
≥512

≥540

≥512

11
≥512

320

≥512

11
32

160

256

11
256

≥640

≥512

11
≥512

320

256

11
256

≥640

≥512

11
≥512

≥640

256

11
≥512

320

≥512

11
256

≥640

64

11
256

≥640

128

11
≥512

320

256

11
128

≥640

≥512

11
128

320

≥512

11
≥512

≥640

256

11
256

≥640

≥512

11
64

320

≥512

12

Determination of Maintenance of Post-Vaccinal Serum Antibody Levels

Current practice often combines clinical judgment and client wishes to determine the need for additional serological viral screening between vaccinations. The MSU VDL offers screening of titers against viral vaccine components to assist with these re-vaccination decisions.

Minimizing the Risk of Adverse Vaccination Reactions in Dogs Previously Showing Them

Although the incidence of adverse vaccination reactions is low, some are life-threatening. Serological testing for antibodies to the components of the core vaccines are a logical alternative to standard re-vaccination of these dogs.

Managing Outbreaks in Shelters

Timely differentiation between seropositive and seronegative animals is an important tool in decision making at shelters experiencing acute infectious disease outbreaks. Animals residing in the shelter that are seronegative or have very low antibody levels can then be separated from those that are seropositive. The seronegative animals cannot be adopted out until they are shown to be seropositive upon retest. Animals coming into a shelter can be admitted if they are seropositive, whereas those testing negative should be vaccinated and admitted only once there is evidence that they seroconverted.

Immunohistochemical Labeling Red For Cdv In The Brain Of A Dog — Immunohistochemical labeling (red) for CDV in the brain of a dog

Segmental Necrohemorrhagic Enteritis In A Dog With Cpv 2 — Segmental necrohemorrhagic enteritis in a dog with CPV-2

Screening Options

The MSU VDL offers vaccine serology screens for both dogs and cats and also offers unique services in the interpretation of leptospirosis vaccine titers. Serum (2 mL) is requested for these tests and this testing can be done in combination with other tests sent to the laboratory, e.g. thyroid function tests.

Canine Vaccine Antibody Panel (80101) includes:

Canine Distemper Virus (CDV) VN (80050)
Canine Adenovirus-2 (CAV-2) VN (80047)
Canine Parvovirus-2 (CPV-2) HI (80054)

Canine Vaccine Panel + Lepto (95996) includes the above plus Leptospirosis (95055).

Revaccination is recommended for dogs with a CDV titer below 32, a CPV-2 titer below 80, and a CAV-2 titer below 16. An interpretation of the leptospirosis titers is provided based on challenge data in vaccinated dogs.

Feline Vaccine Screen (80102) includes:

Feline Herpesvirus-1 (FHV-1) VN (80031)
Feline Calicivirus (FCV) VN (80066)
Feline Panleukopenia Virus (FPV) HI (80035)

We recommend revaccination for cats with an FHV-1 titer below 16, an FCV titer below 32, and an FPV titer below 40.

Collecting and Submitting Samples

Details regarding turnaround time, collection protocol, and requirements for specimens and shipping are available for each test in the MSU VDL catalog. For samples that need to be kept cold during shipment, we recommend using an MSU VDL insulated mailer with pre-paid overnight UPS delivery.

Please contact the MSU VDL Virology Laboratory at 517.353.1683 with questions about test formats, sample handling, etc.

For More Information

American Animal Hospital Association, Vaccination Recommendations for General Practice, https://www.aaha. org/guidelines/canine_vaccination_guidelines/practice_vaccination.aspx

World Small Animal Veterinary Association, Vaccination Guidelines, Vaccination Guidelines for Cats and Dogs 2015, https://www.wsava.org/guidelines/vaccination-guidelines

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