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The Essential Vaccines Your Cat Absolutely Needs

Vaccination is a cornerstone of veterinary medicine. It is the main component of preventive care.

Vaccination not only protects your cat from being infected, but also prevents the spread of infections to other animals and sometimes to humans.

This is a public health issue.

But, it is not recommended to vaccinate with all available vaccines.

Choices have to be made.

A group of veterinary experts, the VGG (Vaccination Guidelines Group) was assigned by the World Small Animal Veterinary Association to write guidelines on vaccination in dogs and cats.

The goal of the VGG was to bring forward recommendations for vaccination programs that would offer maximum protection against infections while trying to minimize the vaccines load.

What is the vaccines load? And why should we minimize it?

The vaccine load represents all the vaccines a cat has received throughout its life.

The 2 reasons why we should try to minimize the number of vaccines are financial and medical.

Financial: some cat owners may consider some vaccination programs too expensive and decide not to comply with the veterinary recommendation.

Medical: it must also be recognized that vaccines do present some risk, even though they are highly beneficial to cats and public health.

For instance, viruses in modified live vaccines may revert back to some degree of virulence and cause symptoms similar to the disease.

Some minor inflammatory or allergic manifestations may occur after vaccines administration such as a transient fever, reddening at the injection site, rash or pain.

There are also some more worrying events, fortunately very rare:

  • an anaphylactic shock, which is an exacerbated allergic reaction and requires urgent veterinary care
  • a cancerous tumor (sarcoma) at the injection site, which is specific to cats. It develops months or years after the administration of a vaccine

How to minimize vaccine load?

The VGG defines two types of vaccines:

Core vaccines: the vaccines that should be administered to ALL cats. These vaccines protect against potentially lethal infectious diseases that have a worldwide distribution.

Non-core vaccines are required for cats whose lifestyle and/or immediate environment put them at risk to get infections.

Core vaccines for cats are discussed in this chapter. They are:

  • Feline parvovirus (FPV), causing feline distemper or feline panleukopenia
  • Feline calicivirus (FCV)
  • Feline herpesvirus-1 (FHV-1)
  • Rabies

Non-core vaccines are discussed in Chapter 6


Cat vaccination schedule

Chart of cat vaccination schedule with core vaccines

In kittens

The core vaccination protocol includes 3 consecutive administrations of the three core vaccines: Feline Panleukopenia Virus (FPV), Feline Calicivirus (FCV), and Feline Herpesvirus (FHV).

The objective is to protect kittens against these viruses as early as possible while trying to avoid the interference of maternal antibodies that prevent a proper immunization.

The first administration is suitable for kittens whose maternal antibodies have waned early. It should take place at 6-8 weeks of age.

The next 2 administrations will follow at 2-4 weeks interval. The last one should not be done before the kitten is 16 weeks of age: there should be no maternal antibodies left. In some situations, where the first injection is done very early, your vet may have to vaccinate your kitten 4 times.

In adult cats

The first administration will be done at one year of age or 12 months after the primary series of vaccinations as a kitten.

A booster of panleukopenia vaccine should be administered every 3 years.

However, the immunity conferred by the herpesvirus and calicivirus vaccines is not as strong as for panleukopenia virus. It is therefore recommended to consider your cat's way of life:

Low risk cats, living solitary (i.e. not with other cats) and not wandering outside the house should be vaccinated every 3 years, with the panleukopenia vaccine

High risk cats are those cats who live in a household with several other cats, or who are allowed to wander outside the house, or are used to visiting from time to time communities of cats such as catteries. These cats need to be vaccinated every year.

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Vaccine injection site in cats

In cats (and dogs), vaccines may cause some adverse events. They are rare, most often mild and temporary. However, exacerbated allergic reactions, which need urgent medical care, may occur.

In cats, another type of adverse event causes a problem. It is a firm and large cancerous tumor that develops at the injection site in 3 to 12 months. It is quite easy to spot on the cat's fur. This is known as the Feline Injection Site Sarcoma (FISS).

Feline Injection Site Sarcomas are very rare. They represent around 2.3% of the adverse events which themselves occur in only 0.05 to 0.5% of the vaccinations.

They do not call the medical benefits of vaccination into question. But this is a reason for NOT over-vaccinating cats and for taking some precautions (WSAVA recommendations):

  • Whenever possible try to avoid vaccines with adjuvant
  • Avoid vaccination in the interscapular region (between the shoulder blades)
  • Prefer subcutaneous to intramuscular injection sites
  • Alternate injection sites

These measures should help limit the chance that your cat gets this tumor.

Note that this kind of tumor can be treated and cured.

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Feline Panleukopenia (FPV)

The feline panleukopenia virus is genetically closely related to the canine parvovirus type 2 (CPV-2).

The feline panleukopenia virus causes the feline infectious enteritis. You can find other names for the same disease: feline parvovirus, feline parvoviral enteritis or feline distemper.

The main consequence of this infection is a decrease in the population of all white blood cells, hence its name, panleukopenia (pan=all leukopenia=low white blood cells count).

Feline Panleukopenia Identity Card


The feline panleukopenia virus is highly contagious.

Infected cats can shed large quantities of the virus, via all types of secretions: feces, urine, oral or nasal discharges. They accumulate rapidly in infected cats' living areas. But virus shedding stops shortly after recovery.

Panleukopenia viruses are very resistant in the outside world. They can survive for months to a year. They can also be disseminated by passive vectors such as shoes, clothes or paws.

In theory, panleukopenia viruses can be destroyed by many kinds of disinfectants (bleach, peroxygen...). In practice, the feedback from catteries or shelters shows it is very difficult to get rid of the infection. This is a reason why it is recommended that all new entrants should be vaccinated.

The new host is contaminated via oral or nasal route.

In a contaminated queen, the virus can cross the placental barrier and infect her fetus where it provokes birth death or abortion.

Mechanism of progression

chart of the cat oronasal cavities

After an incubation period of 2 to 7 days in the oropharynx, where it replicates, the parvovirus can reach any organ:

  • in the small intestine, it shortens the epitheliums villi and causes inflammation (enteritis)
  • in the lymph, it destroys white cells and impairs the immune response
  • in the bone marrow, it hinders the production of blood cells (granulocytes, monocytes, red cells and platelets)
  • in kittens, it can also attack the nervous system


Fortunately, in most cases, there is no symptom at all. All cats that have been infected previously and survived are immunized for the rest of their life.

Kittens or cats of less than 1 year old are more susceptible to the virus. Some of them die suddenly, with no warning.

Others develop fever, depression, anorexia, vomiting after the virus incubation period. Diarrhea and dehydration follow shortly.

The disease will not last longer than a week for those cats that eventually survive.


The diagnosis relies on blood test. Unvaccinated cats with a low blood count cell will be highly suspected to harbor infection.

Confirmation will come from agglutination or immunochromatographic tests.

Treatment and prevention

In case of acute disease, chances of recovery improve if rapid and intense supportive care is provided.

It consists of fluid therapy for rehydration and restoration of electrolyte balance. Because the intestine does not offer a proper barrier to bacterial infections anymore, your vet may also prescribe a wide spectrum antibiotic.

Both attenuated live vaccine and inactivated vaccine are available. Attenuated live vaccine should not be administered to very young kittens of less than 4 weeks, as well as to sick cats or pregnant queens.

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Feline Calicivirus (FCV)

The feline calicivirus is a RNA virus. As such, it can evolve rapidly and attack many different body sites. Its genetic profile varies considerably. It makes the design of a vaccine more difficult: vaccines developers have to find the antigens that are both specific to the virus and common to all its different variants.

Depending on the type of strain infecting the cat patient, the symptoms may vary greatly:

  • A respiratory syndrome which is very similar to the symptoms caused by the feline herpes virus type-1
  • A limping syndrome
  • A virulent systemic infection leading to death
Feline Calicivirus Identity Card


The feline calicivirus is highly contagious.

It can hardly be found in other species than cats, such as dogs for instance. There is no other virus reservoir mammal species except cats themselves. It means that FCV can only be transmitted to a cat by another cat. Humans are not susceptible to this infection.

The virus is shed in the environment with oral and nasal secretions during the infection and usually for one month after recovery. The virus can survive up to one month in the outside environment.

The prevalence of the virus depends on the number of cats in the household, or cattery. Cats kept in small groups have little chance (around 10%) to get infected whereas the proportion can reach 40% or more for cats living in large colonies or shelters.

Permanent calicivirus carrier cats: a minority of cats sheds caliciviruses for their entire life. Those cats contribute to the persistence of the contamination of their living areas, especially in communities of cats.

Disease development and symptoms

The calicivirus enters cats' body through the mouth, nose or eye conjunctiva. It replicates in the oropharynx during 3 to 4 days. From there it may reach other places in the organism such as the lungs and the joints.

The high variability of the virus genome leads to very different diseases.

Oral cavity and upper respiratory tract disease

This is the most common form of the disease. The virus stays within the oral cavity or develops in the respiratory tract. The disease usually resolves in 2 to 3 weeks.

Often, the disease is subclinical: there is no symptom.

In many other cases, vesicles develop on the margins of the tongue. They progress into ulcers. It is a characteristic sign of the infection. It is combined with oral and nasal discharge.

The disease may become more severe in kittens with fever, lack of appetite, and increased salivation. In the youngest animals, pulmonary lesions may occur and cause pneumonia.


It is also called limping syndrome. It follows the oral and respiratory tract disease. Infected cats may limp for a short period of time.

The virus causes a thickening of the synovial membrane and an increase in the synovial fluid quantity that cause the lameness.

FCV virulent systemic disease

You may find other names that describe the same disorder: hemorrhagic-like fever or highly virulent feline calicivirus disease.

In this case, the calicivirus gets to other areas of the body: the pancreas, the spleen, the liver and some parts of the skin (nostrils, ear auricles, footpads).

This form of the disease usually starts with severe respiratory tract symptoms and progresses towards a variety of manifestations:

  • ulcers on the footpads, nose, lips, ears and around the eyes
  • edemas on the head and limbs
  • jaundice
  • circulatory disorders and micro-hemorrhages
  • respiratory distress

This is a very severe disease that often leads to death.

It often occurs as a very rapid outbreak, following the introduction of an infected cat in a colony (shelter, cattery).

Survivors recover rapidly.


A positive serologic test is not enough to make sure that the symptoms are caused by the feline calicivirus. This is because there are a lot of cats that are FCV-positive but hardly get any symptom. Some of them shed a lot of viruses without any manifestation of the disease: they are the carriers discussed earlier in this chapter.

On the opposite, a negative serology doesn't prove that FCV is not responsible for the signs that your cat may display: there are so many different forms of the virus that tests may not recognize some antibodies.

Usually the veterinarian performs two successive tests. If the titers (the quantity) of FCV antibodies increase dramatically from the first test to the next and that the symptoms are consistent with a calicivirus infection, your vet will reasonably come to the conclusion that FCV is the cause of the disease.

Treatment and prevention

There are no veterinary antivirals that have proven effective against FCV.

Supportive care is the only option. Depending on the severity of the illness, it may include rehydration by intravenous fluid, a proper palatable diet, large spectrum antibiotics (against pulmonary bacterial superinfection) and anti-inflammatories (against pain and fever).

Vaccination is the mainstay of prevention against calicivirus. Designing a vaccine against FCV is not easy, though. Due to the high variability of this virus' antigens, it is a real challenge to find the antigens that both are specific and can be found in all the variants of the virus.

In the real world, no such vaccine has been designed yet. No available vaccine protects against all the variants of the calicivirus. This has practical implications:

  • even well vaccinated cats may develop calicivirus infections
  • cats surviving from a calicivirus infection are not immunized against a new infection by another strain of calicivirus
  • as available calicivirus vaccines offer a good level of protection for the strains they are designed for, it is better, whenever possible, to alternate the type of vaccine from one booster to the next

For kittens, the first vaccination should be administered at 6-8 weeks of age and then boosters every 2 to 4 week. Hence, 2 to 3 boosters are possible, depending on the age of the primary vaccination.

Individual indoor cats are considered as low-risk cats. They should be vaccinated every 3 years only. High-risk cats are those which live in communities. They should be vaccinated annually. Alternate the types of FCV vaccines if possible.

It is recommended to vaccinate your cat before it visits a cattery.

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Feline Herpesvirus (FHV)

Feline herpesvirus (FHV) is the agent of feline viral rhinotracheitis (FVR).

Feline herpesvirus and feline calicivirus are often associated because they are the two main agents for viral respiratory diseases in cats, and also because many vaccines protect against both pathogens.

These two viruses are very different, however.

In contrast to the feline calicivirus, the herpesvirus is a DNA virus. It is very stable. There are very little genetic variations from one strain to another.

The herpesvirus' remarkable feature is its capacity to enter a latent state, from which it can reactivate in some special conditions.

Feline Herpesvirus Identity Card


The only hosts for the feline herpesvirus are cats. It means that an infected cat necessarily got the virus from another infected cat, let alone some other rare type of felines such as lions, pumas or cheetahs!

Cats shed viruses through their oral or nasal secretions, either during their primary infection or when the virus reactivates.

The virus enters its new host via the mucous membranes of the eye conjunctiva, the nose and/or the mouth. It may also be transmitted by the queen to its kitten in utero, but does not induce abortion.

After the initial acute infection, the virus enters latency. In some circumstances, the dormant virus may reactivate and resume its active, infective phase that causes the symptoms and the shedding of new viruses in the environment.

This happens when the cat is stressed (a change of housing or in its diet, a journey...), when a queen is lactating or pregnant or when a cat receives a treatment with glucocorticoids.

Thus, infected cats are never really cured. At any time, they may return to an acute infective phase.

Disease development and symptoms

The feline herpesvirus replicates in the mucosae of the oral and nasal cavities, of the upper part of the pharynx and of the eye conjunctiva.

It may then colonize the bronchi and the bronchioles in the lungs.

It causes lesions in the tissues by destroying the cells of the mucous membranes.

The acute phase lasts from 10 to 14 days while the cat remains contagious for an extra week.

Then, the virus enters latency in the trigeminal ganglia, nervous ganglia situated behind the eyes and that receive most of the nerves that innervate the face. There, the virus is almost undetectable.

It can reactivate in some special conditions (stress, lactation, medical treatment, immune suppression by the feline leukemia virus (FeLV) or the feline immunodeficiency virus (FIV) - read Chapter 6 on con-core vaccines in cats). The cat may or may not display the clinical signs, but, anyway, will shed viruses in its environment.

The respiratory symptoms correspond to a classical rhinitis with sneezing and serous nasal discharge. Fever and lack of appetite are the most severe manifestations.

The cat may also suffer from eye disorders. They are characteristic of the feline herpesvirus.

Ulcerative keratitis is the most frequent symptom. It consists of an inflammation of the outer layer of the cornea, the transparent layer that covers the eyes. In most case, it is accompanied by an inflammation of the conjunctiva (conjunctivitis) where the virus actively replicates.

There are many other complications:

While the respiratory manifestation of the disease occurs mainly at the primary infection, the ocular disorders affect mainly older cats when the virus reactivates. Very young kittens whose eyes are not yet open provide breeding ground for eyes infection.

Generally, very young animals are more susceptible to viral infections. This is also the case for the herpes virus. Kittens are more susceptible to the disease and the symptoms are more severe. They can even lead to death.


Respiratory symptoms are not different from those caused by other pathogens: the feline calicivirus or respiratory bacteria.

Associated eye disorders suggest the implication of the herpesvirus. It should be confirmed by laboratory exams. The method of choice is PCR (Polymerase Chain Reaction) that detects the presence of the virus' DNA from a swab of the cat's mouth mucosa.

Unfortunately, a positive result doesn't necessarily mean that the symptoms are caused by the herpesvirus: many cats are healthy carriers and shed herpesviruses intermittently. The presence of the virus may be incidental and not correlated with the symptoms.

The test does not make a difference between antibodies resulting from an infection by a wild virus and those produced by a FHV vaccine.


Some antiviral drugs (cidofovir, famciclovir, human interferon) have shown some level efficacy against the ocular form of the infection. They may be given in combination with boluses of l-lysine.

Supportive treatments are function of the severity of the symptoms. They include:

  • cleaning ocular discharge with eye drops and/or a physiologic solution
  • anti-congestive drugs
  • antibiotics against bacterial superinfection
  • a palatable diet; it is important that infected cats eat well
  • a fluid therapy for the most severe cases


All cats should be vaccinated against the feline herpesvirus, because the virus is highly contagious, and may cause a severe disease especially in kittens and older cats. In addition, it is ineradicable once it has entered latency.

FHV vaccines are often combined with calicivirus vaccines. They are made of attenuated or inactivated virus and are, most of the case, injectable. Some intranasal vaccines are available.

The immunity conferred by the vaccine is not very strong. Therefore, cats with high risk of infection should receive a booster every year. Individual cats living alone in the household may be revaccinated every 3 years only.

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Feline Rabies

For many reasons, rabies holds a special place among pets' infectious diseases.

The rabies virus is always fatal for any mammal species, including humans.

The rabies virus can be transmitted directly from a cat (or a dog) to a human.

Rabies vaccine is a milestone in vaccination history: rabies vaccine was the first vaccine that could be used in animals (Pasteur 1885).

In addition, rabies vaccine is the only pet vaccine that is mandatory in many US states or in many other countries around the world.

Feline Rabies Virus Identity Card


The rabies virus is present in the saliva of infected animals. It is transmitted to a new animal through the open wound caused by a bite.

Theoretically, rabies can affect any warm-blooded animal such as mammals or birds. In real life, infecting animals are most often carnivorous mammals. They have teeth that can easily penetrate through the skin (birds have no teeth).

The virus can't penetrate an intact skin.

As the virus affects the central nervous system, it changes infected animals behavior. They are more aggressive and are no more afraid of attacking bigger animals.

The vast majority of cats and dogs living in developed countries are vaccinated against rabies. This should help completely eradicate the disease. It is the case in some countries of Western Europe such as the UK or France. Unfortunately, in some other countries such as the US, an abundant wild life living close to humans (bats, coyotes, foxes, ferrets, groundhogs) serves as a reservoir for the virus.

Progression of rabies infection

The first step of the infection takes place in the muscular tissues close to the wound site. Here the virus replicates and grows in numbers for a period of 1 to 3 months.

The second step consists of the migration of the virus toward the brain. The virus doesn't move with the blood flow. Instead it uses the nerves route: along the peripheral nerves, the dorsal root ganglia, and the spinal cord to finally reach the brain. By doing so, it doesn't have to face the many sentinels of its host's immune system.

If the bite causing the infection is close to the central nervous system (brain, spinal cord), the rabies virus needs less time to get to the brain.

In the brain, the rabies virus provokes an inflammation (encephalitis). It replicates and disseminates throughout the body.

Very rapidly rabies viruses reach the salivary glands. They concentrate in large numbers in the saliva, ready for infecting a new animal.

Be aware that a cat becomes infective a few days before it displays the signs of the disease.


The symptoms appear long after the cat has been bitten. Depending on the form of the disease, they progress in two or three phases:

First phase: mild, unspecific symptoms. They include anorexia, fever, vomiting and diarrhea. The owner may also notice already some behavioral changes. The cat may become more friendly or, on the contrary, more irritable or excited.

This step doesn't last long. Two days at most.

The furious form is characteristic of the second phase of the disease. Aggressiveness is exacerbated. The cat threatens and attacks on any occasion other animals, humans and even unanimated objects. This behavior is not present in the dumb form or paralytic form of rabies. In this latter case, the cat develops directly the paralytic form.

The third phase is the paralytic and final phase. Paralysis progresses from the throat and the masseter muscles throughout the body to the legs and causes the death of the cat. During this phase, the cat is still contagious even though it is not aggressive. It may still bite or leave some infected saliva on an open wound.

Treatment and prevention

There is no treatment recommended for rabid cats.

The only protection for cats is preventive vaccination. Rabies vaccines are very effective.

Primary vaccination consists of a single shot from 12 weeks of age. Revaccination program should comply with local regulations. It is usually every 1 or 3 years.

If a non-vaccinated cat has been bitten by a rabid or an unknown animal, it is suspected to be rabid. Therefore, it should be euthanized or placed under strict isolation for a period of 6 months and then vaccinated against the rabies virus.

When a human is bitten by an animal, it should be assumed that the animal is rabid. And the person should be vaccinated and treated with rabies antibodies (immunoglobulins), according to the World Health Organization recommendations.

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