Feline Leukemia Vaccination in cats: The Essentials To Know

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Whether indoors or like to wander around on roofs and in gardens, cats have an intense life. It's very simple, they are curious about everything, even if it means putting themselves in danger. For guardians, it's a source of wonder but also a concern. So how does the Feline Leukemia vaccination work?

feline leukemia vaccination
Feline Leukemia Vaccination in cats: The Essentials To Know

Compulsory vaccination: Only the rabies vaccine is mandatory if the cat guardian intends to take it abroad or have it kept by an animal pension. If the other vaccines are not compulsory, you should not forget that they are offered to guardians to protect their animals from fatal diseases

How is leucosis transmitted?

It takes prolonged contact for the virus to be transmitted. In the first case, a kitten can be born carrying the virus because its mother contaminated it during gestation.

Next, that is the problem; because it sums up the lives of cats; sometimes, all it takes is a scratch, bite, or a coat cleaning session by a cat friend to be contaminated.

Even if you have had your cat for years and he lives in a house or apartment, maybe he is a carrier of this terrible disease.

feline leukemia vaccinationIs there a way to protect cats against leucosis?

The fact that carrying out your kitten's primary feline leukemia vaccination can be an opportunity to know whether or not he has feline leukosis.

For this, the veterinarian will take a blood sample. If this practitioner has the necessary equipment to examine the blood sample, it will be fixed after about ten minutes. Otherwise, you will have to wait for the result from an analysis laboratory.

If your cat tests negative, rejoice because you can protect him against this deadly disease by doing feline leukemia vaccination to him.

Is Feline Leukemia vaccination for cats compulsory?

Only the rabies vaccine is mandatory if the cat's guardian intends to take it abroad or have it kept by an animal pension.

In these two cases, you will be required to have carried out the first Feline Leukemia vaccination, but also all the reminders and to have microchipped your cat; as indicated by the passport that the veterinarian will issue to you for this purpose.

If the other vaccines are not compulsory, you should not forget that they are offered to guardians to protect their animals from fatal diseases.

feline leukemia vaccination

What are the other deadly cat diseases?

After rabies and leucosis, your cat can contract cat coryza, feline typhus, or cat infectious peritonitis.

All these diseases leave little chance, or none, to your cat if he catches them. They can be caught by direct contact (bite, scratch) or indirect (via your shoes, etc.).

Symptoms are most often painful for your cat. Some of these diseases lead to the appearance of bloody diarrhea. Your weakened cat will no longer have the strength to eat until it dies.

You can avoid all of this by vaccinating your pet.

At what age should my cat be vaccinated against leucosis?

After reading about how leucosis is caught and what it can cause your cat, you've decided to have it vaccinated.

You will have to wait two months to be able to do so. It is precise during this first meeting between your kitten and the veterinarian that you will be able to know if he is already a carrier or not.

A second injection must then be given about a month later. This delay can vary between 3 and 4 weeks, depending on the vaccine. Again, your veterinarian will explain the protocol to follow.

I have had a cat for several years, is it too late to have it vaccinated?

You probably know the adage: better late than never. It applies very well to the vaccination of your animal. For example, if you decide to vaccinate your cat, you will strengthen its immune system regardless of age.

Likewise, after spending several years vaccinating your cat, you wonder if it is still helpful to do so on an aging animal; the answer is yes. It is even desired.

As age comes, your cat becomes, and it is understandable, less resistant to disease in general. However, continuing to vaccinate him can allow him to end his life peacefully without contracting a virus or other pathology that his vaccines can avoid.

feline leukemia vaccination

My cat has caught leucosis: will he die?

Cats can react differently to leucosis, some being more severe if they have it all their lives. As mentioned before, they are more susceptible to certain infections, meaning some symptoms might not be as noticeable. We can talk about gingivitis, and toxoplasmosis, among others.

Others may experience symptoms for a few years before finally seeing the signs.

Finally, some cats will show the first symptoms after two years, such as tumors in their mouths or other physical issues. These cats become more fragile over time, so you do have to take care of them a bit more.

There is no cure for leucosis once the cat is a carrier. However, a veterinarian can apply a care protocol to mitigate the effects of different pathologies.

Antiviral treatment is little practiced because the side effects are almost as bad for the cat as the viral infection itself.

We can help strengthen our immune defenses thanks to treatments and treat related diseases.

The cat's diet will play a significant role in your cat's ability to live better with the disease. It will be necessary to avoid giving him raw meat. The latter can give him internal parasites (worms).

Having leukosis puts your cat at greater risk of having internal and external parasites. Therefore, it will be necessary to deworm it regularly. We understand the importance of vaccination.

Why is vaccination indicated?

The purpose of vaccinating your pet is to protect it against the main potentially fatal viral or infectious diseases to which it may be exposed during its lifetime.

Vaccination also makes it possible to reduce the prevalence of each disease within the feline population and to prevent the reappearance of serious diseases.

Similarly, for vaccination to remain effective, it must be practiced throughout the life of your companions. The protocol is adapted according to their place, lifestyle, and age.

In addition, vaccination involves a vaccination consultation, an opportunity to carry out a complete clinical examination of your animal, and to answer any questions concerning its diet, behavior, activities, identification, sterilization, or aging, depending on his age.

What are the effects of the vaccine on my cat?

Each vaccine will specifically stimulate the animal's immune system. This means of defense against the infectious agent through the synthesis of antibodies and the mobilization of cells (macrophages, lymphocytes) directed against this contagious agent makes it possible to prevent the development of the disease against which we vaccinate. The animal, therefore, will not present the disease or a milder form of it.

There are vaccines against viruses or even bacteria, some of which can be combined during the exact vaccination consultation.

Who to vaccinate and how?

All cats must be vaccinated throughout their lives!!!

Even if your cat does not go outside, indirect transmission of certain viruses via your contaminated clothes or shoes, your visitors, remains possible.

Young people and seniors are most at risk due to the respective fragility of their age-related immune systems. Also stopping vaccinating an old cat is a mistake.

The choice of vaccines will be made according to your animal's environment and lifestyle, and therefore the resulting risks.

For the vaccine to be effective and to protect it properly, it must stimulate the immune system in sufficient quality and for a long time. For this, reminders according to a very specific schedule must be respected under penalty of failure of the protocol.

Their frequency again varies depending on the type of vaccine, your cat's risk of exposure, and its age.

For the most common vaccines, the first vaccination is carried out from the age of 2 months (except for Rabies from 3 months) with a booster one month later followed by annual boosters.

A vaccine carried out very young (less than 2 months) is recommended on certain farms but cannot be considered a primary vaccination because of the risk of interaction with the antibodies transmitted by the mother. This is why your veterinarian may need to repeat the protocol from the start so that immunity sets in properly.

Even if the first 3 vaccine injections are not carried out scrupulously respecting the dates, the immunity will be insufficient, the injections carried out useless and the protocol will have to be repeated from the start.

Be careful to mark these dates on your diaries or mobile phones with an alert!!

During the primary vaccination, you will be issued with a health record that will follow your animal throughout its life and on which the vaccination stickers will be affixed. A European passport may also be issued during rabies vaccination.

From when is my cat considered protected?

It is only about 15 days after the second primary vaccination injection that the kitten acquires theoretically sufficient immunity to protect it until the following year, the date of its annual booster.

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What diseases are vaccinated?

Diseases that are deadly and easily transmitted within the feline population are affected by vaccination.

Cats are vaccinated against panleukopenia or " typhus ", coryza, chlamydia, and feline leucosis.

The rabies vaccine is intended for animals that travel and leave French territory, provided they are identified (electronic chip, tattoo).

On the vaccination sticker, each disease is identified by a letter, often the first letter of the name of the disease.

Thus a cat vaccinated with a CRP +/- Leu vaccine is vaccinated against Calicivirosis (C) and Infectious rhinotracheitis (R), both agents of the " coryza " complex, feline panleukopenia (P) and, if it has access to the exterior, Feline Leukosis (Leu) transmitted by Feline Leukemogenic Virus or " FeLV ". Unfortunately, we do not yet have a vaccine against the feline equivalent of HIV, FIV, or feline immunodeficiency virus.

Adding Rage(R) or Chlamidiosis (Ch) valences depends on where your pet lives and geographical movements.

The main characteristics of each of these conditions are listed below:


It is not a disease but a syndrome characterized by ocular, nasal, or even oral involvement following the action of one or more viral and bacterial agents belonging to this complex. Thus we can meet caliciviruses, herpesviruses, and sometimes chlamydiosis (bacteria).

This "coryza" results in red and runny eyes, nasal discharge with stuffy nose and sneezing, and even gingivitis, sometimes associated with mouth ulcers responsible for bad breath, salivation, and difficulty eating. 

The severity of "coryza" varies greatly depending on the viruses present and the receptivity of the cat, ranging from benign transient and self-resolving forms to forms that persist chronically. These are highly contagious diseases because they are transmitted by inhalation of contaminated air or contact with contaminated surfaces and clothing. Therefore, its diagnosis requires the realization of conjunctival or intraoral samples or even a blood test and the direct search (PCR method) or/and indirect (assay of antibodies) of viruses and bacteria.

The treatment of this disease is symptomatic (anti-inflammatory, antibiotics) or even specific (anti-virals, antibiotics against chlamydiosis).

Therefore, vaccination allows for avoiding contamination and chronic carriage, even if its effectiveness remains limited and does not prevent 100% from being infected. However, the resulting disease will be much less severe in the latter case. Please note that Chlamydiosis is transmissible to humans and is characterized by mild conjunctivitis.

Feline Panleukopenia or Typhus

It is not a fatal disease that has become rare thanks to the generalization of vaccination but which can occasionally reappear in the event of relaxation.

This disease is highly contagious and caused by a reasonably resistant parvovirus. It results in severe, hemorrhagic gastroenteritis associated with a fall in white blood cells and fever leading in 90% of cases to the death of kittens and young adults. Transmission occurs through direct (inhalation, ingestion) or indirect (via soiled surfaces and clothing) contact with contaminated secretions or stools.

Its diagnosis combines convergence of clinical signs with biological results and direct (PCR) or indirect (Rapid ELISA test) detection of the virus from the stool.

The treatment of this disease is most often symptomatic (hospitalization for rehydration, antibiotics, antiemetic and diarrheal). You can also use omega interferon, but it is an expensive molecule that does not systematically lead to a cure.

Prevention involves maintaining early and systematic vaccination, respecting hygiene rules (isolation, specific single-use care equipment), and disinfection (bleach) when a cat is infected.

Vaccination is considered adequate and should be carried out systematically.


Feline Leukosis

This disease results from an infestation by a retrovirus : FeLV, or feline leukemogenic virus. It is responsible for a deficit of immunity (which promotes the appearance of all kinds of diseases), anemia, and/or blood tumors.

All bodily fluids can transmit the virus: saliva (bites, licking, standard bowls), urine and stool (typical litter), blood (bites, from mother to fetus, blood transfusion), semen, and secretions vaginal (reproduction), mother's milk (breastfeeding kittens). On the other hand, the virus being fragile, contamination requires direct contact from cat to cat.

If he is positive but without symptoms, he will have to be tested again four months later to know if he remains a chronic carrier of the virus or not. A direct search (5PCR method) for the virus is also possible from specific lesions or liquids if necessary.

The background treatment uses feline omega interferon, but the results are inconsistent. Most often, treatment is symptomatic and aims to combat opportunistic infections.

The vaccine against feline leukosis provides good protection, even if it is not 100%. Kittens can be vaccinated from the age of 2 months.

Prevention involves carrying out a rapid test for any new kitten adopted, especially before introduction into a family of several individuals or a breeding farm.

Sterilization, which reduces runaways and fights between cats, is also essential. Cats infected with FeLV should stay indoors to be further protected against opportunistic infections and avoid contaminating other purchases. They must also be vaccinated against other diseases (Not FeLV, it is useless) and dewormed more often.

The FeLV virus is not transmissible to humans.

FIV feline immunodeficiency virus

This widespread retrovirus is transmitted by biting or mating.

It is responsible for a " Cat AIDS " disease but is not transmissible to humans. Currently, no vaccine effective against FIV is available in France despite its use in some countries (the USA, among others).

After contamination, the virus can remain dormant for years, never express itself, or cause a late loss of immunity (opportunistic infections) or tumor complications.

The main symptoms of FIV infection are progressive weight loss, anemia, persistent or recurrent fever, repeated infections, autoimmune diseases, blood tumors, and behavioral disorders.

Diagnosis can be made in the clinic using the same rapid tests as those for FeLV or by direct (PCR method) or indirect (serology) detection of the virus in the blood.

A kitten less than six months old and cheerful during screening but healthy will have to be retested a few months later because of a risk of false positives by interference with the anti-FIV antibodies transmitted by its mother. Similarly, a cat suspected of being infected and harmful to the test must be tested again at least three months later.

Treatment is symptomatic (treatment of secondary infections or anti-cancer) combined if necessary with high-dose feline omega interferon or even low-dose human interferon, provided that these products are implemented early on in cats with mild symptoms.

Prevention: Isolated from contact with other cats. Sterilize it to avoid escape and transmission by mating. Monitor him and regularly have blood samples taken for hematological control. Deworm and vaccinate. 


Rabies is a severe contagious disease, transmissible to humans, which results in nervous disorders leading inevitably to death in dogs, cats, and humans.

It is subject to strict health surveillance, which requires vaccination for all cats living in an area declared infected, and mandatory health monitoring over 15 days of any biting animal.

Vaccination is compulsory for any border crossing or trip abroad, for cats participating in an exhibition, and can be requested during campsites or boarding house stays.

Some countries also require a blood test for rabies antibody testing one month after the last vaccine injection and before importing the animal to check that the rabies vaccine has "worked".

The rabies vaccine requires only one annual injection, performed at three months.

Are there any negative side effects associated with vaccination?

Some cats, fortunately, few, may show hypersensitivity of their subcutaneous tissue to any type of injection, including vaccines. This will result in the appearance of an inflammatory nodule at the injection site, a nodule that will generally regress within a month. Nevertheless, this individual sensitivity may be a predisposing factor for the future development of a malignant tumor: feline fibrosarcoma.

The benefit/risk of vaccination on cats presenting this type of reaction is, therefore, to be defined, the precautionary principle, especially if it is an indoor cat, being to stop vaccinating these animals.

Severe side reactions (allergic shock, itching, facial edema, hematological disorders) are described but remain exceptional and occur quickly after the injection. It is, therefore, advisable to plan to monitor your animal in the hours following the injection and not hesitate to bring it back to us if this type of manifestation occurs.

Therefore, vaccination retains its interest in preventing the most severe diseases. It must be adapted on a case-by-case basis according to your animal's habits and living environment.

Don't forget to deworm your cat the week before the annual vaccination appointment, and bring your vaccination card or passport on D-Day. 

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