Rabbit Vaccine Immunity

How the BunnyVac Works, and its Limitations

Vaccine Immunity: How the Pasteurella multocida vaccine, Bunnyvac, functions to protect a healthy rabbit from pasteurellosis, advantages and potential drawbacks.

Rabbit with facial abscess and wet nose. Bunnyvac might clear up the nose but likely not any skin infections caused by P. multocida strains, suggests Mr. Glass.

The following is the substance of interviews and written communications by Mr. Robert Glass, inventor of the Pasteurella multocida vaccine, BunnyVac, which help explain how the BunnyVac rabbit vaccine immunity works. 

{My impressions and conclusions, drawn from registered nursing experience, are below in parenthetical italics. Emphases are mine}.

Quoting Mr. Robert Glass: 
“Pasteurella has two pathology modes: skin infections (abscesses) and respiratory infections (lungs, airways, sinuses). The site of infection appears to be at least partially determined by the strain of Pasteurella - certain strains have an affinity for infecting the skin, others have an affinity for the mucous membranes of the respiratory system (lungs/nasal passage/sinuses). The skin strains appear to be more closely related to each other than they are to the respiratory strains and the same is true of the respiratory strains.

“We have focused on the respiratory strains with this vaccine. Since they are fairly closely related, it is possible to induce antibodies that will recognize and fight many in the respiratory group. Thus we can produce a vaccine that offers some level of benefit for many if not all of the respiratory strains.”

{The pasteurella strains that cause skin and other abscesses therefore are not the ones targeted by the BunnyVac, and the vaccine should successfully target at least “most” of the respiratory strains.}

“The immunity induced by infection or by vaccination is present in the blood stream in the form of antibodies (humoral immunity) and immune active cells (cellular immunity). In many cases the cellular immunity is more effective than the humoral."

{In other words, reinforcing cellular immunity through breeding toward a genetically strong immune system is an excellent strategy over the long term.}

“Antibodies can directly kill bacteria but they also serve to 'tag' bacteria so the immune cells can 'see' them. The cells are very effective because they not only kill the bacteria but also engulf the bacteria, digest it and send pieces out in 'packets' which are taken in by not-yet-activated immune cells which become imprinted with the bacteria's pieces and so join the fight.

BunnyVac Logo

“The problem with Pasteurella infection is that the bacteria can be attacked only in those areas where there is good blood supply. Unfortunately, Pasteurella also colonizes the sinus cavities where there is very limited blood supply. In this area the immune cells and antibodies are not able to get to all the bacteria, thus the carrier state.

“This is also why many rabbits initially have really snotty noses and congestion; this is due to infection in the nasal passages and lungs. The immune response can kill the bacteria in these areas and the symptoms clear. But the bacteria remain in the sinuses. Then the immune response goes into a 'surveillance' mode with a lower number of activated cells and decreased antibody levels. It does maintain a memory of the infecting agent and can be activated by re-exposure. So, the carrier rabbit is asymptomatic until something allows the bacteria to multiply once again. In rabbits this is 'stress' in any of many forms...."

{So, vaccination of symptomatic (sick) rabbits results in elimination of symptoms because the germs in the lungs and nose are eradicated. But at the same time, P. multocida continues to colonize the sinuses. This is called a carrier state.

This description of immune system function describes cellular (natural) immunity. Humeral (vaccine) immunity exhibits a 'memory' that wanes over time. Vaccination induces the immune response, but the white blood cells eventually 'forget' their assignments. This is why yearly doses are required.

Lastly, even vaccinated rabbits under stress can begin showing symptoms due to an increase in bacterial load.}

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“The purpose of the vaccine is to induce a level of immunity in non-infected rabbits so that an initial exposure to live Pasteurella finds them with enough antibodies to block the infection. We do not know what percentage of (vaccinated) animals will emerge from an initial exposure without becoming carriers; that will be the subject of a further study.

"What we do know is that the severity of an initial exposure (in vaccinated healthy rabbits) will not result in death and the degree of disease will be significantly reduced. This implies less infectious snot in the air from sneezing which in turn means less chance that additional rabbits will become infected, especially because they also will have an existing immunity.”

(End of Mr. Glass quotations.)

{By "existing immunity," this is intended to mean, "are also vaccinated." What about those rabbits in your barn that aren't vaccinated?? Wouldn’t you like them to have excellent intrinsic immunity? Excellent intrinsic immunity is a result of selective breeding (not vaccination), and eliminates the need for vaccine immunity.}

{I have no plans to vaccinate any of my rabbits, at least until all the data is in. Instead, I'll continue doing what I've done for years - support my herd's native health through selective breeding of healthy rabbits only.}

Vaccine immunity only works when the immune system is functioning adequately, usually achieved in bunnies by 7 weeks of age.

This little pet bunny is only 5 weeks old.

Some rabbits are born with weak immunity. If the immune system is inadequate whether in animals young or adult, vaccine immunity will not be conferred due to the inability of the immune system to recognize a threat and produce antibodies.

Using the BunnyVac Vaccine Off-Label: Producing Carrier Rabbits

The term "off-label" refers to vaccinating symptomatic (sick) rabbits with the hope that the symptoms will go away. And sometimes this works and the sneezing stops.

It is very tempting to vaccinate a sick rabbit in order to cure it. Hello, breeders: Vaccination is never a cure. Recent anecdotal reports support the idea that such off-label use, rather than curing rabbits, will only create silent P. multocida carriers.

Unfortunately, the following scenario has played out in multiple rabbitries, according to multiple rabbit breeder sources:

• Breeder A vaccinates his sick rabbits, which eliminates symptoms in some of them. (He mistakenly believes they are cured.)
• Breeder B purchases 2 of these previously sick but now asymptomatic, vaccinated rabbits. She wisely quarantines the rabbits for a month. Since the rabbits remain asymptomatic, she moves them into the main rabbitry.
• About two weeks later, multiple rabbits in the herd begin sneezing and exhibiting a purulent nasal discharge, including the herd buck, a pregnant doe, and several other high-quality rabbits.

Clearly, the two vaccinated rabbits purchased by Breeder B were shedding P. multocida everywhere they went despite being asymptomatic. 

How Vaccine Immunity Eliminates Symptoms Without Curing the Infection

The Bunnyvac floods the rabbit with tagged pieces of dead bacteria, which stimulates the rabbit’s immune system to create antibodies to this pathogen. This helps the body to identify and eradicate an active infection in all those areas of the body where the immune system can find the bacteria. At the same time, it is well understood that in areas of low blood flow, for example, the sinuses, the infection continues to safely hide from an immune system onslaught.

As a result, the infection is reduced to a sub-clinical state (appears to be "cured"), and the rabbit’s immune system, if strong enough, rebounds, controlling most or all symptoms. If this rabbit had Pasteurellosis, or was a carrier before vaccination, the vaccination could act as a therapeutic agent which reduces the bacterial load without eliminating bacteria in areas of low blood flow, such as the sinuses.

For as long as the antibody titer remains high, any leakage of germs from their hiding places results in swift eradication. Should the vaccine "wear off" or the rabbit undergo stress such as a fright or a pregnancy, the vaccinated, once-sick rabbit may become symptomatic again.

For these reasons, it is unwise to use BunnyVac in a show rabbit herd.

Until the studies have been done that demonstrate the ability of BunnyVac or any vaccine to eradicate P. multocida, the breeder should not trust BunnyVac to CURE anything.

Please remember: the vaccine needs to be renewed yearly.

In a breeding herd, use selective breeding rather than vaccination in order to strengthen the innate immune function in your rabbits.

BunnyVac Vaccination Label. Click the pic to view at full size.

Induce Vaccine Immunity (Off Label) in
Pet Rabbits

Since the BunnyVac (for vaccine immunity) is licensed for use only in healthy rabbits to prevent Pasteurellosis, vaccinating a sick rabbit to “cure” Pasteurellosis is considered “off-label,” or, not its intended purpose. Nevertheless, off-label use of the BunnyVac to stimulate vaccine immunity in sick rabbits has been practiced, resulting in the elimination of symptoms. The vaccinated rabbit will seem to be healthy.

I can think of a good use for off-label vaccination: To improve quality of life in pet rabbits!

Imagine vaccinating your sick pet rabbit and all its symptoms go away! With the BunnyVac, according to Mr. Bob Glass, this is a possibility, as long as your rabbit's immune system is at least adequate to start with, and as long as you can repeat the vaccination once a year to keep your rabbit's antibody titers sufficiently elevated. The Bunnyvac may be able to prolong the rabbit's quality of life and the pet owner's enjoyment of his pet rabbit for perhaps several more years. 

See BunnyVac for details, warnings, indications and contraindications for using BunnyVac off-label in pet rabbits.

Raising rabbits? Consider a membership to the American Rabbit Breeders Association