Canine Distemper in Depth and the Vaccines

Dogs infected with canine distemper virus (CDV) can suffer lifelong complications or even die from the disease. First, we will discuss the disease and the available vaccines against this debilitating and often fatal disease.

Distemper Virus Infection Route

CDV is found worldwide and circulates amongst wild animals such as foxes, wolves, coyotes, raccoons, skunks, minks, and ferrets. The most common route of infection for companion dogs is airborne through either the sneezing or coughing from an infected animal including another dog. Shared water or food bowls can also be a source of transmitting the disease.

Initial Symptoms of Distemper

At first, CDV-infected dogs typically will develop a watery to pus-like discharge from their eyes. Secondly, they develop fever, nasal discharge, coughing, lethargy, reduced appetite, and vomiting. Then, it progressively affects the central nervous system (CNS).

Distemper Virus Infection Is Systemic

CDV attacks the respiratory, gastrointestinal and CNS.

Central Nervous System

Once the disease progresses to the CNS, dogs will develop muscle twitches, head tilts, convulsions, seizures and paralysis. If on the rare occasion a dog recovers from the disease, he will more than likely have lifelong episodes of seizures and muscle twitches.

Hard Pad Disease

The nickname for distemper virus infection is “hard pad disease” because the virus may cause paw pads to thicken and harden.

Contagious Infection

Infected dogs are contagious before they even develop signs of the disease. Dogs with confirmed diagnoses will need to be isolated from other animals for at least two weeks. If a dog has neurological symptoms, they can still pass along the virus for months.

Prevention

Vaccinating dogs against CDV is the best course of action.

Distemper Virus Vaccination Protocol

Below is Dr. W. Jean Dodds’ vaccination protocol against CDV.

9 – 10 weeks of age
Distemper + Parvovirus, MLV

14 – 15 weeks of age
Distemper + Parvovirus, MLV

18 weeks of age
Parvovirus only, MLV

1 year old
Distemper + Parvovirus, MLV
This is an optional booster or titer. If the client intends not to booster after this optional booster or intends to retest titers in another three years, this optional booster given at puberty is wise.

Distemper Vaccines

Distemper is commonly combined with vaccines against parvovirus, parainfluenza, and adenovirus-2 which provides cross-protection against infectious canine hepatitis (adenovirus-1). Typically, these are written as DHPP or DAPP.

At this time, the only combined distemper and parvovirus vaccine (DPV) that fits Dr. Dodds’ protocol is manufactured by Merck (Nobivac DPV).

Alternate Vaccination Protocol

Let’s pretend you are unable to obtain the Nobivac DPV vaccine. Does this affect Dr. Dodds’ protocol? Yes; it can.

Almost all vaccine vials or sprays contain additional ingredients to make sure the vaccine “takes” in the body. When you add too many vials and/or sprays together all at once, the likelihood of an adverse vaccine reaction increases.

NeoTech is the only manufacturer that has a standalone CDV vaccine called NeoVac-D. Zoetis also makes a CDV vaccine which comes together with the measles virus for puppies (Vanguard DM).

Boehringer Ingelheim, NeoTech, Elanco, Merck, and Zoetis each have a monovalent parvovirus (CPV) vaccine.

6 – 7 weeks of age
Parvovirus vaccine

9 weeks of age
Distemper vaccine
10 – 14 days after the parvovirus vaccine

11 weeks of age
Parvovirus vaccine
10 – 14 days after the distemper vaccine

12 weeks of age
Distemper vaccine

14-16 weeks of age
Parvovirus vaccine

Because of the current highly virulent CPV strains, some veterinarians, breeders, and pet caregivers choose to give another monovalent CPV booster at 18-20 weeks.

Distemper Virus Vaccine Safety

The risk of an adverse event to the current CDV vaccine is low. However, CDV vaccines should never be given before 6 weeks of age as they can cause severe post-vaccinal encephalitis (PVE).

Depending on the strain used to vaccinate against CDV, the rate of a reaction to the Rockborn and Snyder Hill strain is ~ 1:100,000. To put that in perspective, let’s pretend that the estimated 90,000,000 million companion dogs in the United States were vaccinated for the first time on the same day with one of these strains. It is estimated that 900 will have a serious adverse event like PVE which can cause blindness and death.

Let’s now pretend that the Onderstepoort strain was used. The rate of reaction is ~ 1:500,000. In perspective, that is 180 companion dogs out of the 90,000,000. However, this strain is less potent against CDV.

When the distemper vaccine is combined with the adenovirus-2 vaccine, the risk of immune suppression and PVE increases – particularly in puppies. This is one reason why Dr. Dodds’ does not advocate for the combination of the two at that age.

While these vaccines are relatively safe with low incidence rates of serious adverse events, they could be safer. The recombinant canine distemper vaccine (rCDV) cannot cause PVE.

Unfortunately, the manufacturer, Boehringer Ingelheim, no longer makes rCDV or a combined recombinant distemper and parvovirus. Their Recombitek C3 (CDV, Adenovirus -2, and CPV) has the fewest vaccine antigens.

Vaccine Non-Responders

A vaccine non-responder has a genetic trait that prevents him from mounting immunity to the disease from the vaccine. In companion dogs – particularly Greyhounds – the rate is ~1:5,000 for the CDV vaccine. For CPV, Dobermann Pinchers, Rottweilers and Black Labrador Retrievers are more likely to be non-responders with an estimated prevalence of ~1:1,000.

These dogs will always be susceptible to either CDV or CPV, respectively and should not be used for breeding. However, they can still live a fulfilling life and be fairly well protected because the population ‘herd’ around them have been vaccinated and immunized.

Sterilizing Immunity

The CDV and CPV vaccines produce what is termed ‘sterilizing immunity’. Sterilizing immunity typically lasts between 5-7 years. Companion dogs that are responders to these vaccines and were actually immunized have sterilizing immunity that not only prevents clinical disease but also prevents them from being infected with either virus.

The American Animal Hospital Association’s canine vaccination guidelines committee recommends vaccinating against distemper every 3 years after the initial puppy shots. They appear to want more research to confirm the duration of immunity against distemper.

Dr. Dodds understands their position. However, since the duration of sterilizing immunity is clearly longer than 3 years, she prefers serum antibody titer testing due to potential vaccinal adverse events performed every three years or more often until geriatric age, to determine if a vaccine is necessary.

Serum Antibody Titer Testing

Antibody titer testing alleviates the question whether a companion adult dog is protected from disease plus reduces the possibility of adverse events in an already immunized dog.

Adverse Events in an Immunized Dog

Vaccinating an immunized companion dog animal would cause only a temporary increase in antibody titer, and hypersensitivity reactions to vaccine components (e.g. fetal calf serum) may develop. Furthermore, the animal doesn’t need to be revaccinated and should not be revaccinated since the vaccine could cause an adverse reaction.

References

Dodds, W. Jean. “Vaccinating Against Infectious Canine Hepatitis.” Hemopet, 14 Mar. 2021, https://hemopet.org/vaccinating-against-infectious-canine-hepatitis/

Dodds, W Jean. “Early Life Vaccination of Companion Animal Pets.” Vaccines vol. 9,2 92. 27 Jan. 2021, doi:10.3390/vaccines9020092, https://www.mdpi.com/2076-393X/9/2/92.

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