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Vaccines

Vaccines for Dogs

What is a vaccine
The word vaccine comes from the Latin word "vacca", which means cow. An English country doctor, Dr. Edward Jenner, discovered that people given a preparation or vaccine of material from the common cattle disease, cowpox or vaccinia, developed only a mild skin infection, but when those vaccinated individuals were exposed to the deadly smallpox virus (a virus closely related to cowpox), they remained healthy, or were immune. More than one hundred years after Jenner's findings, the great French scientist Louis Pasteur and his colleagues found that they could protect animals and people against a variety of diseases, including rabies, by administering injections of the infectious microorganism in an altered form. The two main alterations of these microorganisms were "inactivated vaccines" using killed virus or "attenuated vaccines" using virus that was still living but was changed into a harmless form.

What is "immunity"
Immunity is a complex series of defense mechanisms by which an animal is able to resist a disease or infection or, at least resist the harmful consequences of the infection. The main components of these defenses are the white blood cells, especially lymphocytes and their chemical products, including antibodies and cytokines such as interferon. All infectious disease organisms (viruses, bacteria, protozoa, fungi, etc.) have specific components called antigens. These antigens will cause lymphocytes to respond in a specific way such that each antigen stimulates the production of a mirror-image antibody, as well as non-antibody responses called cellular immunity. Immunity has memory, so that a subsequent exposure to the same antigen results in a much more rapid response. This rapid response usually stops the new infection before it can cause serious illness in the individual. Such immune memory can fade with time, sometimes quite rapidly, depending on the specific antigen-antibody relationship.

"Immunity has memory."

Immunity is not absolute. Immunity can sometimes be overwhelmed when there is exposure to a high dose of a virulent or particularly harmful strain of the microorganism, or when the animal is unduly stressed or is immunosuppressed because of another disease or certain drugs.

Why are vaccines administered by injection
Some vaccines are given locally, for example into the nose, but most require injection so that the maximum take-up of vaccine by the white cells and stimulation of the immune system is achieved. Some vaccines are injected subcutaneously or just under the skin, others are injected into the muscles or intramuscularly. Injections may look easy, but your veterinarian considers many variables before they are administered.

Why is more than one dose of vaccine given to pups
There are two reasons. First, without complicated testing it is impossible to know when a pup has lost the passive protection it gets from its mother. An early decline in a puppy's maternal antibody can leave it susceptible to infection at a very young age: a strong maternal immunity can actually interfere with early vaccination (see our handout Vaccination Failure). Second, particularly with killed vaccines, the first dose is a "priming" dose, and the second dose boosts the response to a higher, longer-lasting level of immunity.

Why does my dog need to be revaccinated

"Immunity does decline with time and this decline rate varies with individuals."

In most properly vaccinated dogs, the immunity should last more than a year, and often several years. However, immunity does decline with time and this decline rate varies with individuals. To maintain the best immunity in a reasonable way, revaccinations have proven very successful. Because the vaccines we use are continuously improving, some do not need to be given as often, depending on individual circumstances. Most dogs with low-risk lifestyles can be vaccinated every three years with the "core" vaccines and as needed for any "non-core" vaccines (most non-core vaccines require annual boosters). Your veterinarian will discuss the need and frequency of booster vaccinations for your dog based on your pet's needs and lifestyle.

How long does it take a vaccine to produce immunity

"It usually requires ten to fourteen days before a reasonable level of protection is established."

Within a few hours of vaccination, the earliest phases of the immune response are being stimulated. It usually requires ten to fourteen days before a reasonable level of protection is established. Killed vaccines may not provide adequate protection until after the second dose. In young puppies, maternal antibody may hinder protection until later in the vaccine series. Therefore, it is advisable to keep even a vaccinated pup away from dogs or pups of unknown vaccination history until it has finished its vaccination course.

What happens if my dog is sick when vaccinated
The veterinary check-up prior to vaccination and sometimes pre-vaccination blood tests help prevent this situation. In most cases, minor illness would not have disastrous consequences, but it is important that an animal is healthy when vaccinated, to ensure proper development of immunity.

Will vaccination make my dog sick
Some dogs develop mild lethargy or soreness in the day or so after vaccination. In the case of killed vaccines containing an adjuvant, some thickening or lump formation may occur at the vaccination site. If this is painful or persists for more than a week or so with no decrease in size, consult your veterinarian. A few dogs will develop more severe reactions that are forms of hypersensitivity (allergy). These will usually occur within minutes, but may be delayed for a few hours. The dog may salivate, vomit, develop diarrhea or have difficulty breathing. Should this occur, consult your veterinarian immediately.

Do vaccines provide 100% protection
Vaccines have been highly successful in protecting the majority of dogs against disease. As a direct result of vaccination, diseases such as distemper that were once common are now rare. But there are situations in which the immunity conferred by a vaccine may be overcome and a vaccinated dog may still develop disease. In such cases the disease is generally milder than it would have been had the dog not been vaccinated.

Some causes for apparent "vaccine failure" are:

Maternally derived antibodies - As mentioned above, when a puppy is born and after it suckles its mother, it acquires a proportion of any antibodies that the mother has. A well-vaccinated female will confer antibodies to her puppies for the diseases she has been vaccinated against, as well as any others she has acquired naturally. Such antibodies protect the pup against those diseases for the first two or three months of its life, the most critical time. However, during this same period the maternally derived antibodies can block the pup's ability to respond to vaccination. This blocking effect decreases as the maternal antibody gradually disappears over those two to three months. A point in time is reached when vaccination can be successfully given. Unfortunately, this point varies between pups, mainly because the amount of maternal antibodies that each pup receives is variable. This is part of the reason that most "puppy programs" involve a series of vaccinations, given two to four weeks apart. Maternal antibody interference has been a particular problem with canine parvovirus vaccination.

"Maternal antibody interference has been a particular problem with canine parvovirus vaccination."

Incomplete immune response - There is variation between dogs in their immune system. Some respond less well to vaccination, so immunity may be incomplete or shorter-lived than normal. Certain breeds and genetic lines have a tendency for such problems.

Declining immunity - Without booster vaccinations or the natural boosting of immunity by sporadic exposure to the infectious agent in nature, immunity to the specific organism declines over time. This is particularly true in older dogs. If there is a particularly heavy dose of a specific organism in the environment, the pet's declining immunity may be insufficient and become overwhelmed, resulting in disease.

Immune suppression - Certain infections and some drugs, such as anti-cancer drugs, may cause a suppression of the immune system so that an otherwise well-vaccinated dog becomes susceptible to infection and disease if exposed.

New strains of organism - Some infectious agents exist in different strains or evolve into new strains that are not directly covered by the vaccines given. In these cases, the vaccine may give some 'cross-protection', but protection may not be complete.

The above are not the only reasons for vaccination "failure", but they are the most likely explanations.

If you feel your dog has contracted an infection for which it has been vaccinated, let your veterinarian know. Tests can be undertaken to try to establish why vaccination has failed to be protective.

This client information sheet is based on material written by: Ernest Ward, DVM
© Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.

Vaccines for Cats

Recent advances in veterinary medical science have resulted in an increase in the number and type of vaccines that are available for use in cats, and improvements are continuously being made in their safety and efficacy. Veterinarians routinely recommend certain vaccines for all cats (called 'core' vaccines) whereas others are used more selectively according to circumstances.

"In all cases the selection of the correct vaccination program for each individual cat, including the frequency of repeat, or booster, vaccinations, requires professional advice."

However, in all cases the selection of the correct vaccination program for each individual cat, including the frequency of repeat, or booster, vaccinations, requires professional advice.

At this time, "core" Vaccines, as recommended by the American Association of Feline Practitioners (AAFP) for all kittens and cats, include:

1. Feline panleukopenia, FPV or FPL (also called feline infectious enteritis or feline distemper) caused by FPL virus or feline parvovirus (FPLV)

2. Feline viral rhinotracheitis, FVR caused by FVR virus, also known as herpes virus type 1, FHV-1

3. Feline caliciviral disease caused by various strains of Feline caliciviruses, FCV

4. Rabies caused by Rabies virus

"Non-core" or discretionary vaccines, as recommended by the AAFP for kittens and cats with a realistic risk of exposure to specific diseases:

1. Feline chlamydiosis caused by Chlamydophila felis infection

2. Feline leukemia disease complex caused by Feline leukemia virus (FeLV)

3. Feline Infectious Peritonitis (FIP) caused by FIP virus or Feline Coronavirus

4. Bordetellosis caused by the bacterium Bordetella bronchiseptica

5. Feline Immunodeficiency Virus (FIV)

Vaccines that are not recommended by the AAFP, but that may be appropriate under certain conditions include:

1. Giardiasis caused by the protozoan parasite Giardia lamblia

2. Ringworm

How do vaccines work
Vaccines work by stimulating the body's immune system to produce antibodies to a particular microorganism such as a virus, bacteria, or other infectious organism. The animal's immune system is then primed, or prepared to react to a future infection with that microorganism. "This reaction will either prevent infection or lessen the severity of infection and promote rapid recovery." This reaction will either prevent infection or lessen the severity of infection and promote rapid recovery. In other words, vaccination mimics or simulates the protection (immunity) that a pet has once it has recovered from natural infection with a particular infectious agent. The immune system is complex, involving interaction of various cells and tissues in an animal. The main cells involved in an immune reaction are the white blood cells and the main tissues are the lymphoid tissues such as the lymph nodes. One of the most important functions of the immune system is the production of specific protein molecules called antibodies. A specific microorganism, such as Feline Panleukopenia Virus, has components called antigens. When a foreign antigen is introduced into the body, the immune system will produce an antibody that specifically binds and neutralizes that specific antigen and no other. The body produces several different types of antibodies. Other white blood cells such as lymphocytes are able to identify and kill cells that have become infected by the microorganism. This activity of lymphocytes and other immune system cells is called cell-mediated immunity. After vaccination, just as after recovery from natural infection, the body 'remembers' the specific antigens so that when they are encountered again it can mount a rapid and strong immune response, preventing the cat from developing the disease. The duration of this response varies with the disease, the type of vaccine and other variables. The likely duration will determine the recommended revaccination date. "...most vaccines work by preventing your cat from becoming ill during a subsequent exposure to specific disease-causing organisms..." It is important to realize that most vaccines work by preventing your cat from becoming ill during a subsequent exposure to specific disease-causing organisms, but vaccination may not prevent the cat from becoming infected. In such cases the cat, while itself protected against disease, may shed the organism for a short time after exposure and be capable of infecting other susceptible animals. This is not a major consideration in the pet cat but may be important in the breeding colony.

When should my kitten be vaccinated
Generally, kittens are vaccinated for the first time at between six and eight weeks of age and booster doses are given at ten to twelve weeks and sometimes again at fourteen to sixteen weeks. A kitten will not be fully protected until seven to ten days after the second vaccination. Under specific circumstances, your veterinarian may advise an alternative regime.

How often should booster vaccinations be given
In the past, veterinarians recommended booster vaccinations for cats on a yearly basis. However, as research into vaccines progresses, recommendations for frequency of boosters continue to evolve. The appropriate interval for boosters will vary with individual circumstances. "If your cat is at higher risk for realistic exposure to a disease, the more frequent vaccination may be recommended." Most adult cats that received the full booster series of vaccines as kittens should be re-vaccinated every one to three years based on lifestyle risk assessment. That is, if your cat is at higher risk for realistic exposure to a disease, the more frequent vaccination may be recommended. It is important to thoroughly discuss your cat's lifestyle with your veterinarian and determine the appropriate vaccinations and vaccination schedule for your cat. The AAFP vaccination guidelines recommend that low-risk adult cats be vaccinated every three years for the "core" vaccines and then as determined by your veterinarian for any "non-core" vaccinations. Some vaccine manufacturers have developed approved three-year vaccines for many of the core antigens. It is important to note that feline leukemia virus (FeLV) vaccine is recommended by some AAFP members to be a "core" vaccine while other experts classify it as a "non-core" vaccine. Your veterinarian is the ultimate authority on how your cat should be vaccinated

Will vaccination always protect my cat
Vaccination will protect the vast majority of cats but under some circumstances, vaccine breakdowns will occur. Reasons for such breakdowns or apparent 'vaccine failure' include:

Variations between different strains of viruses - This is particularly a problem for example with feline calicivirus infections, where, like the "common cold" in people, there are a large number of different strains. Available vaccines may only partially cross-protect against some of these strains.

Maternally derived antibodies - Kittens acquire a proportion of "maternal antibodies" from the mother (through the uterus before birth and from the milk during nursing). A well-vaccinated queen passes antibodies to the diseases she has been vaccinated against, and any others she has acquired naturally. Such antibodies protect the kitten against those diseases for the first two or three months of life, arguably the most critical period. However, during this same period, the maternally derived antibodies can block the effects of vaccination of the kitten. This blocking effect decreases as the maternal antibodies gradually disappear over those two to three months. A point in time is reached when vaccination can be successfully given. Unfortunately, this point varies between kittens, mainly because the amount of maternal antibodies that each kitten receives is variable. For this reason, vaccinations are usually given two to four weeks apart in the kitten vaccination program.

The cat was stressed or not completely healthy at the time of vaccination - Stress can prevent a good response to vaccination. For this reason, it is better to let a kitten settle into its new home for five to seven days before a vaccination is given. Before administering a vaccination, your veterinarian will perform a complete physical examination to help ensure that there are no signs of clinical disease.

The cat has been exposed to an excessive challenge dose of virus or bacteria in its environment and this has been sufficient to overwhelm the immunity.

The immune system of the cat is under-performing or incompetent because of some other disease, or complications associated with advanced age.

These are not the only reasons for vaccination failure but they are the most common.

If you feel your cat has contracted an infection for which it has been vaccinated then let your veterinarian know so tests can be undertaken to try to establish why vaccination has failed to be protective.

What are the risks of vaccination
There are very few risks to vaccination. Your veterinarian will be able to advise you on specific details concerning your pet. You may notice your cat has a temporary loss of appetite or is less lively a day or two after a vaccination, but this should resolve within twenty-four to forty-eight hours. A very few cats may be allergic to one or more components of the vaccine and have more serious side effects such as difficulty in breathing, vomiting or diarrhea. If these signs occur, let your veterinarian know immediately. A rare form of soft tissue sarcoma known as "vaccine-associated" or "injection-site" fibrosarcoma has been associated with a reaction to vaccine components or medication in a very small number of genetically susceptible cats. This association is controversial, and studies are in progress to investigate whether the association is real. The benefits of vaccination greatly outweigh these small risks in most situations (for further information, see the handout Post-vaccination Sarcoma).

Which are the most important vaccinations to have
The answer to this difficult question depends on individual circumstances, including the area you live in and the lifestyle of your cat.

"Certain vaccines are more routinely given and are regarded as "core" vaccines."

As mentioned before, certain vaccines are more routinely given and are regarded as "core" vaccines. Others may or may not be advised, depending on the particular situation of your cat. Your veterinarian will be able to advise you of the most appropriate vaccination schedule for your cat.

Feline panleukopenia infection - FPV or FPVThis is anuncommon disease today because of widespread vaccination, but the risk remains widespread. When disease occurs, it is a severe and often fatal gastroenteritis (stomach and intestinal infection), with profound depression, dehydration and collapse. It is very contagious to other cats. Vaccination provides a high level of long lasting protection.

Feline respiratory virus infection
Disease is caused by FVR virus (FHV-1) or the caliciviruses (FCV) - sometimes simultaneously. The syndrome is commonly termed Upper Respiratory Infection (URI) or sometimes, erroneously, "Cat Flu". While not usually very serious, except in young kittens, it is a very common infection in unvaccinated cats and can cause long-term problems. Vaccination is only moderately effective as solid immunity to these viruses is not long term, and may be overcome by a high dose of virus in the immediate environment. Vaccination significantly reduces the severity and duration of URI.

Feline chlamydiosis
This tends to be a particular problem in colony cats or in certain geographical locations. Chlamydiosis is a bacterial infection due to the organism Chlamydophila felis, which causes a painful inflammation and swelling of the conjunctiva or the membrane around the eye as well as upper respiratory infections. It has also been associated with infertility in queens. Infection in colonies of cats can last for long periods because protection against re-infection (immunity) is relatively short lived. Vaccination can help to prevent infection becoming established in a colony and can be used in conjunction with treatment where infection is already present.

Feline leukemia virus (FeLV) infection
This virus is widespread and infection of outdoor cats or cats in infected catteries is common. The vast majority of persistently infected cats will die either from tumors or because of the immunosuppression caused by the viral infection. Current vaccines provide a good level of protection and do not interfere with routine testing for the virus in breeding colonies. Because the virus tends to take many months before it causes disease, infected cats can appear completely normal and healthy. For this reason, your veterinarian may suggest your cat have a blood test to make sure it is not infected before vaccination. Despite vaccination, a few cats will still become infected with the virus.

Feline Infectious Peritonitis (FIP)
FIP is caused by a coronavirus. Infection with the causative or related viruses is common, but the disease is uncommon, although cases occur from time to time almost everywhere. We do not understand why some infections lead to fatal disease whereas the majority of infections cause only minor illness. Vaccines may be advised in some high-risk situations.

Rabies
This is such an important disease because of the almost 100% fatality rate of cases once symptoms occur, and because of its potential transmission to people by bites from infected animals. Rabies vaccination is an essential part of the vaccination program for all cats.

This client information sheet is based on material written by: Ernest Ward, DVM
© Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.

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