Allergic Reactions Shock And Anaphylaxis In Your Dog Cat Or Ferret

Vaccine Reactions

Ron Hines DVM PhD

  Is One Size Vaccine Dose Really Right For All Dogs?  

Another Entrée With The Same Flavor  

 A Science-Based Pet Vaccination Program 

What Is Anaphylaxis?

Anaphylaxis is a sudden and violent allergic reaction to a normally harmless substance (an allergen ) that has been introduced into your pet’s body. It is a more severe form of the milder and slower phenomenon, common allergies . Common allergies in your dog are much more common. The usually take the form of itchy skin, itchy ears, and itchy congested eyes.  Cats suffer the same problem, but their respiratory tract as well as their skin, can be the primary target. When it is your pet’s digestive system that is the target, vomiting and diarrhea are the common symptoms. In between the two are hives  – more rapid and intense than allergies, less severe than anaphylaxis. All three share a common immunological pathway and the milder forms can be a prelude to the more severe ones. 

Most allergens are complex proteins. They are substances that the immune systems of a few pets and people mistakenly classify as “foreign and dangerous” but which cause no response in the majority of pets and people. A potential anaphylactic allergen can be a drug, an insect sting, a vaccine component, a food ingredient – any product containing large complex organic molecules that manages to enter the body.

Allergens cause the body to produce antibodies (immunoglobulins of the E class IgE ). These IgE antibodies reside on the surface receptors of cells in your pet’s blood called basophils and  tissue cells called mast cells. When these IgE coated receptors encounter the specific antigen they were designed to recognize, it causes these cells to release powerful inflammatory chemicals (degranulate). Depending on the amount of these inflammatory chemicals, where in the body they are primarily release and the speed with which they are released, these compounds will cause anything from a mild itch to negative changes in your pet’s heart function, blood pressure , blood vessel permeability as well as injury to surrounding tissue. These are the visible and invisible components of anaphylaxis. 

Allergic Reactions To Vaccinations Are Not Uncommon 

We tend to think of dog, cat and ferret vaccines and anaphylaxis together – although many things from bee stings to food can trigger anaphylactic events. (read here) A critically important factor in anaphylaxis is the genetic susceptibility of your pet. (read here) We tend to link vaccines and anaphylaxis together because the cause and effect are so obvious and dramatic and because a known chain of decisions led to the event. 

But there is more than just dramatics in linking veterinary vaccines and anaphylaxis. The mass production of the virus and bacteria that are required in the manufacture of vaccines requires a complicated “brewing” processes. In that process, many other potentially allergenic proteins are added: living cell from various species other than dogs and cats, bovine serum albumin,  embryonating chicken eggs or fibroblasts all to allow the tissue culture cells and the pathogenic organisms they contain to grow and multiply. Attempts are always made to remove as much of these extraneous ingredients from the final vaccine products as  possible. But those attempts are never 100% successful and a primed immune system in a dog, cat or ferret can recognize exquisitely small residual amounts. 

Most veterinarians believe that when  anaphylactic  reactions do occur subsequent to a vaccination, they are due to ingredients of four kinds. I mentioned some of them required to make vaccines in the previous paragraph.

The next, are called adjuvants . Adjuvants have traditionally been added to vaccines to increase their potency. Some commonly used adjuvants are aluminum hydroxide, aluminum phosphate, calcium phosphate, mineral and peanut oil. But many others have been used as well. Adjuvants intensify the reactions of  your pet’s immune system. One might say that they are an immune system wake up call.  

The next are preservatives and stabilizers. They are added to insure the products remain sterile and have as long a shelf life as possible. The most common preservative once used in vaccines intended for humans was thiomersal/ thimerosal . Thiomersal, a mercury-containing compound, is no longer added to single-dose human vaccines due to long term health concerns. But of this writing, thiomersal is still added to Boehringer Ingelheim’s SoloJec10® dog vaccines and Merck’s Nobivac® Rabies vaccine. You will have to do the research as to what the vaccines you contemplate giving your pet contain. Much of that information is proprietary – a trade secret. Many vaccines also contain gelatin as a stabilizer (read here)  In vaccines intended for humans, gelatin is the single largest identifiable source of severe allergic vaccine reactions. (read here) No similar studies that I know of have been performed in dogs, cats or ferrets. If your pet has allergies to specific animal meats, gelatin-containing products could also trigger an anaphylactic cascade. The immune system is known to recognizes the difference between beef origin and pork origin gelatin or just generic slaughterhouse gelatin. It is unlikely that any veterinary pharmaceutical company is going to reveal their gelatin source or even if it contains gelatin. A history of tick bites increases the chances of gelatin-related anaphylactic vaccine reactions in humans. That could conceivably occur in our dogs and cats as well. No veterinary research has been done. The tick/gelatin connection is called the  α-Gal syndrome  . ( read about it here & here

The last ingredient, antibiotics, are also added to minimize the possibility that bacteria will be carried into your pet’s body with the hypodermic needle. The most common antibiotic added to veterinary vaccines is gentamycin. In many cases, I am told that the addition of antibiotics and antiseptic ingredients were mandated by the Federal Government (USDA/FDA/EMA). 

When a vaccine contains killed bacteria, the proteins in those bacteria have the potential to cause anaphylactic reactions in themselves. I believe that such is the case when veterinary vaccines contain the killed leptospirosis organism or protein-containing fragments of it. That type of vaccine is called a bacterin. It contains every protein that was present in the living disease organism. (read here) In one study, scientists identified  3,654 distinct leptospirosis proteins. (read here) That is probably why canine vaccines that contain leptospirosis pack such a wallop (a heavy blow) to your dog’s immune system. There is plenty of room for improvement but no motivation for the pharmaceutical companies to do so. (read here)

Well, I Read That Anaphylactic Reactions Never Occur During A Pet’s First Exposure To A Vaccine And This Was My Pet’s First time Getting That Shot!

Pets and people are not believed to produce anaphylactic reactions until the second or more time that their immune system encounters a particular foreign protein.  Until recently, veterinarians just called these mysterious first-encounter vaccine reactions “anaphylactoid” (anaphylactic-like) reactions. We now know that they are probably both based on IgE antibody-induced mast cell degranulation. There are several way a “first time” experience vaccine reaction can occur. It might be that your pet had already become allergic to an ingredient in the vaccine – one of the many vaccine ingredients I already mentioned.  It might have been that the vaccine contained a protein very similar to some other protein you pet was already allergic too. I mentioned the tick/beef allergy connection and that no one has explored that in dogs. Some IgE antibodies a pet might possess are promiscuous. That is, the antibody alerts the immune system to more than one distinct antigen protein. (read here) IgE antibodies, the basis of all anaphylactic reactions. are know to occasionally be promiscuous. Some veterinarians in Brazil learned that when they found that the cattle they had recently vaccinated against leptospirosis began to give false positive antibody tests for brucellosis. The cows antibodies were cross reacting.  (read here)     

What Are My Pet’s Options?

1) Minimize the number of unnecessary vaccines your pet receives. Three year-approve rabies vaccines exist. Unfortunately you will need to ask your local officials it they still require yearly rabies vaccination. There is no common policy within the United States. States, counties and cities set their own policies. After your pet’s first year, yearly vaccination against the common viral diseases of dogs and cats is completely unnecessary – despite reminders you may receive from your veterinarian. Does you physician send you yearly reminders to receive yearly polio, hepatitis and tetanus boosters? (read here & here) You are urged to receive your yearly flu shot only because virus mutation causes a new strain of flu virus requiring a different vaccine to appears every autumn.  New strains of dog, cat and ferret virus that override your pet’s initial vaccine series have not been recorded since Louis Pasteur experimented with the first rabies vaccine in 1884. Pet vaccine failures are human failures: vaccines improperly handled, given at the wrong age (too young), given improperly, improperly stored, given after the pet was already incubating the disease, given to a pet with a defective immune system, and perhaps even a compounding error in a production batch at the factory. ( read here ) Your pets 3-shot “pediatric” series should prevent any of those problems. A single booster vaccination in its elder years might be wise as well. (read here)

2) When a vaccine is given to your pet, be sure that equipment and medications to manage an anaphylactic crisis are readily available to the veterinarian. They are often not available at vaccination clinics that move from place to place. (see here) Ask before frequenting these sites – better yet, just avoid them.

3) If your pet had a prior confirmed vaccine reaction or if it acted as if it might have had a reaction on a previous vaccination, discuss having your pet pre-medicated with an injectable or oral antihistamine. This is no guarantee that a serious reaction will not occur, but it might lessen the severity. Remember, the severity of reactions to vaccinations and other foreign protein exposures tend to get worse with repeated exposures. Consider that first mild reaction, a warning ticket from your friendly traffic policeman. The next time he stops you he will probably not be as friendly. 

4) Be particularly vigilant if you know that siblings or parents of your pet have had vaccine reactions. 

5) Inquire if your State or City Health Department exempts reaction-prone pets from rabies vaccinations.

6) Whenever available,  intranasal vaccines which require no injection at all might be a better choice.

7) When in doubt or conflicted, as your veterinarian to run antibody titre tests on your pet to verify that booster vaccinations are unnecessary. The problem with those tests is that they fail to measure immunological memory. Antibody titres naturally drop as time goes by, but protective immunological memory persists.  

The Symptoms of Anaphylaxis In Your Pet:

The symptoms of traditional anaphylaxis occur in your pet within one hour of exposure to the allergen whatever the source. The most common form I see in my practice is anaphylaxis brought on by a booster vaccination. These reactions occur very rapidly – usually within thirty seconds. When they do not meet the time factor or symptomatology of true anaphylaxis. I suspect that many of these reactions are at least partially psychological in nature because they usually occur in fearful or high-strung pets. This doesn’t mean they are not real. Fear causes the release of many physiological mediator chemicals that make drug reactions more likely and sometimes worse. In mild cases, the only signs are low fevers, sluggishness and loss of appetite. Pets that develop a mild first case often go on to develop more severe cases during subsequent exposure to the allergen. In addition to these signs, moderate cases often develop urticaria, which is also called “goose bumps” hives or wheals. These raised patches develop over the head and trunk. Urticaria is a more common sign in dogs than in cats or ferrets. In anaphylaxis, the lips of dogs and cats may also become reddened and puffy. With time, areas of urticaria usually become intensely itchy and later peel like a sunburn.

If your pet is experiencing a severe cases of anaphylaxis, the first sign will often be a rapid drop in blood pressure. This causes its gums to become pale and it’s breathing to become rapid and difficult.  The pet often urinates, defecates and vomits in response to the histamine release. The pet’s heartbeat is often rapid, weak, or irregular and they often appear uncoordinated, restless and frightened. Bloody diarrhea or dark stools may follow. When swelling of the larynx occurs these pets can die due to their inability to breathe. In the most severe cases, shock, collapse, convulsions and coma, can occur. Sometimes the pet’s temperature falls to subnormal while others they run fevers.

Vaccination Reactions In Ferrets:

Throughout the early period beginning in the 1950s, ferrets gradually became common household pets in the United States. The vaccine that veterinarians gave them to protect against canine distemper (read here) was developed for the fur farm fox industry.  Although the company selling the vaccine strongly denied it for 20+ years, the vaccine caused an unacceptably high number of anaphylactic episodes in ferrets. Signs of anaphylactic reaction in ferrets are hyperemia (bright red gums), salivation, swelling of the face and feet, dyspnea (difficulty breathing), and vomiting. Fortunately, an acceptable vaccine with low incidence of anaphylactic reactions became available, PUREVAX® Ferret Distemper vaccine. It is a living canarypox-vectored vaccine. The harmless (other than to birds) virus has been bioengineered to contain two specific glycoproteins  found on the surface of the canine distemper virus.  At the time it was produced by Merial Pharmaceuticals (in 2017 Merial was acquired by Boehringer Ingelheim). It is not a large profit-earner of Boehringer. So there have been long periods over the years when it was unavailable. That vaccine causes much fewer anaphylactic reactions. Another vaccine, Nobivac PuppyDPv® manufactured by Merck is a non-certified alternative. No matter which is used, it is not in your ferrets interest to receive booster vaccinations after its series of juvenile vaccination.  Doing so is just tempting Fate. For rabies protection, I administer Emrab3®. Again, you will have to discuss with your governmental authorities how frequently your location requires rabies vaccination in domestic ferrets.   

What You Can I Do when An Anaphylaxis Event Occurs?

Get your pet to your veterinarian as quickly as possible. Get someone else to drive you. On the way, stroke and reassure your pet and try to keep it calm. Place it on a blanket on its side with its rear legs slightly elevated. Loosen its collar. If it feels chilled, cover it. Do not give it anything by mouth – including water. If it stops breathing, begin CPR. Always remember that agitated and frightened pets will sometimes bite the ones they love. Take precautions.

What Your Veterinarian Will Do:

A severe anaphylactic reaction is a veterinary emergency. Do not take a seat in the waiting room – ask that the veterinarian’s receptionist to see your pet immediately. Call ahead to alert them if you can. If your pet is having difficulty breathing through its swollen larynx, the veterinarian will insert a tube down its windpipe. A drop in blood pressure and circulatory collapse starve the body of oxygen. This can be usually be corrected when the pet is placed in an oxygen-rich environment. Liver and intestines are particularly affected in anaphylaxis. Capillary blood vesicles throughout the body become more permeable and leak blood serum into the tissues. To counteract this, intravenous fluids are usually given rapidly and in rather large quantities. These pets need to be closely monitored so as not to over-flood their lungs with fluid ( pulmonary edema ). Balanced salt solutions and fluids such as Ringer’s solution are often given to counteract circulatory collapse. Urination is a good sign that fluids are working. Colloidal fluids such as polysaccharide, dextran or hetastarch, are preferable to saline solutions because they do not leave the circulation (leak out) as rapidly as Ringer’s solutions. Many advanced centers use them when they think they are more appropriate. Many of these pets receive injections of epinephrine . This compound, normally produced by the adrenal gland, increases heart rate and blood pressure and slows mast cell disintegration. Besides oxygen  intravenous administration of rapid-acting steroids such as prednisolone sodium succinate ( SoluDeltaCortef® ) or dexamethasone sodium phosphate (Decadron®) are often given. At the same time your pet  probably will receive an injection of antihistamine ( perhaps chlorpheniramine maleate/Chlor-Trimeton® or diphenhydramine/Benadryl®). Pets that have abnormally low body temperature (hypothermic) need warmth. Pets with a body temperature above 105 F (40.5 C) need to be rubbed down with iced water or chilled soaked towels. Pets are often given an injection of a penicillin-like antibiotics to prevent secondary infections related to increased intestinal and pulmonary leakage.

Complications Of Anaphylaxis:

Sometimes nothing a veterinarian can do will stop the cascade of events that make up an anaphylactic episode. If this cascade can not be stopped, the pet will die or be left irreparably damaged. The liver suffers greatly during anaphylactic shock. It is the primary“shock-affected organ” in the body. This is because liver cells are very sensitive to oxygen deprivation (see the tests). When the pet’s stomach and intestines do not receive enough oxygen during an anaphylactic crisis, their cells may die leading to fatal ulcers. These pets may vomit bloody mucous and/or pass blood in their stools. In some cases bacteria gain access to the abdominal cavity (peritonitis) through these ulcerated areas. In some cases entire segments of the intestine die. Another result of anaphylaxis can be a condition called disseminated intravascular coagulation (DIC). In this condition, pooled blood coagulates within the vessels of the circulatory system leading to a deficiency in platelets. Without sufficient platelets, hemorrhages occur throughout the body. This can also be fatal.

Are There Ways To Prevent An Anaphylactic Reaction?

Be sure to let your veterinarian know if your pet experienced any abnormalities subsequent to any injection in the past. Do not be afraid to request that your pet be premedicated with antihistamines. 

Unfortunately, most cases of anaphylaxis are not expected. Pets can receive identical vaccinations for a number of years with no problems only to subsequently develop symptoms. Once a dog, cat or ferret has developed an anaphylactic reaction to vaccinations, I no longer suggest periodic booster shots. The only vaccine I will administer to these pets is a periodic rabies booster as the law required. The offending brand of vaccine that caused anaphylactic or other undesirable effects in your pet should never again be used again. 

When I  have a vague premonition that a vaccination reaction might occur, I pre-medicate the pet with an injection of antihistamines 30 minutes prior to vaccination. Then I administer the smallest possible amount of the vaccine with a low dose syringe and observe the pet for an hour. If no reaction has occurred I give the remainder of the vaccine. When a pet has developed an anaphylactic reaction to an insect sting or bite, I phone a prescription in to the owner’s pharmacy for an EpiPen®. This pen-shaped device is an auto-injector that administers epinephrine when tapped against the skin. I prescribe the junior size for cats and small dogs and the adult size for larger animals.

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