Home » other animals » Leukemia in cats FeLV: symptoms and treatment [Wet medicine Krystyna Skiersinis

Leukemia in cats FeLV: symptoms and treatment [Wet medicine Krystyna Skiersinis

Feline viral leukemia FeLV is an infectious and still incurable disease, widespread in the cat community.

Leukemia in a felv cat. How to protect a kitten from her

You know that statistically 25% of cats show clinical signs leukemia FeLV he will die within one year and the remaining 75% will be fighting for another 2-3 years.

What is this insidious, contagious disease entity? What are the symptoms of viral leukemia and how you can prevent your cat from catching it?

You will find the answers to these questions in my article.

It's 1964. William Jarrett, a Scottish veterinary pathologist and his team make a groundbreaking discovery.

Researchers observe that tiny viral particles are budding on the surface of the membrane of cancerous lymphoblasts isolated from a cat with lymphoma.

Experimental virus injection causes the development of a malignant neoplastic process in completely healthy cats!

It turns out that long-term diagnosed domestic feline lymphomas are caused by an infectious agent in the form of the feline leukemia virus.

This revelation revolutionized the current approach of scientists to epidemiology and initiated the rapid development of this field in both veterinary and human medicine.

  • What is FeLV feline leukemia?
  • A bit of history, or where the FeLV came from?
  • How can my cat get viral leukemia?
  • The mechanism of the formation of leukemia in a cat
    • Factors favoring the development of feline leukemia
  • What the feline body does to protect itself from the virus?
    • Fighting the virus
    • The virus spreads through the blood
    • Bone marrow infection
    • Dormant FeLV activation
  • Signs of leukemia in cats
    • The risk of developing neoplasms
    • Hematological disorders not related to neoplasia
    • Weakening of the immune system
    • Skin diseases
    • Immunological diseases
    • Other syndromes
  • Diagnosis of feline leukemia
    • When is the best time to have a blood test for leukemia?
  • My cat is FeLV positive. What's next?
  • Treatment of cat leukemia
    • Leukemia in a cat, antiviral treatment
    • Leukemia in the cat, immunomodulating treatment
    • Fighting diseases accompanying FeLV infection
  • To prevent infection with feline leukemia
    • Vaccination of leukemia in cats
  • Is there anything to worry about?

What is FeLV feline leukemia?

Feline Leukemia Virus - the retrovirus responsible for the disease, belongs to oncornaviruses (i.e. viruses with the ability to cause cancer).

In the course of infection, the immune system is impaired, anemia and / or lymphoma develops (you can learn more about it in the article "Lymphoma in a cat. Symptoms and prognosis ").

What is feline leukemia

FelV occurs worldwide, in some countries it is still believed to be the cause of the most fatal disease in domestic cats.

The incidence in Europe is low (

Currently, thanks to widespread diagnostic tests, infection control and routine vaccination, this dangerous phenomenon has significantly decreased in scale.

A bit of history, or where the FeLV came from?

Approximate time of "birth" of the virus is 10 million years ago (Late Pleistocene).

This infectious particle was supposed to evolve from a virus found in the ancestor of rats, and cats were most likely infected by ingestion or through bite wounds inflicted by rats.

Due to the dry and desert climate in North Africa, the spread of the virus within the cat population was very limited.

How can my cat get viral leukemia?

How can a cat become infected with felv

At present, things are a bit different. Infections with the feline leukemia virus are recorded worldwide, and the disease is spreading in the animal population as a result of close contacts between infected and susceptible individuals.

The virus is transmitted through saliva as well as blood. Social behavior typical of cats, such as grooming each other, sharing bowls for food and water, or fighting, greatly contributes to the spread of disease.

The iatrogenic route of viral transmission is also possible, e.g. through infected needles or during blood transfusions.

Fleas may also be potential vectors of the virus, but it is not known whether this method of spreading is relevant in vivo.

The virus can be found in all body fluids, secretions and excreta, but is not transmitted in urine and faeces.

Due to the way the virus spreads, the incidence of the disease is higher in cats leaving the house, especially in non-castrated cats (wandering, fighting).

Cats of all ages are sick, but kittens are the most susceptible to infection.

The mechanism of cat leukemia formation

Factors favoring the development of feline leukemia

Factors favoring the development of felv

Whether or not you develop clinical leukemia after exposure to the virus depends on several factors.

  1. First of all, immune status - cats with weakened immunity, weak or treated with glucocorticosteroids are more likely to develop all kinds of infections, including leukemia.
  2. The age of the animal is most susceptible to young kittens up to 16 weeks of age. With age, immunity increases.
  3. The virulence of the virus.
  4. Infectious dose.
  5. The severity of the infection.

After infection, which occurs most often through the oral or nasal cavity, the virus aims to increase the size of its "population " as quickly as possible.

This is called viral replication and takes place in the lymphoid tissue of the mouth and throat.

The very penetration of the virus into the body, its multiplication and spreading is a highly thought-out "war tactic ", and each stage of expansion is characterized by an incredible ability to bypass the body's defenses. It is amazing how this clever retrovirus uses the components and mechanisms of individual tissues and organs for its own purposes.

What the feline body does to protect itself from the virus?

How the cat's body can defend itself against the leukemia virus

The following scenarios are possible:

Fighting the virus

In cats with a properly functioning immune system, viral replication is inhibited by cellular mechanisms.

Such cats will fight the virus within a few months, and the immunity obtained in this way will protect against further infection, even for a period of several years.

So we have a win-win situation - such a cat remains healthy.

The virus spreads through the blood

The virus spreads through the blood

If the immune system's response is for some reason too weak to fight off the virus, it spreads throughout the body.

The retrovirus brazenly uses blood cells for expansion - lymphocytes and monocytes, and through them travels to various tissues (e.g. to the thymus, spleen, lymph nodes, salivary glands).

This phase of the virus spreading through the body and its presence in the bloodstream is called viremia.

In most cats, this condition lasts approx 3-6 weeks (maximum 16 weeks).

What is happening to our pet at this time? Initially, the following may occur:

  • noticeable weakness,
  • fever,
  • enlargement of the lymph nodes.

In addition, the unaware furry sows the virus into the environment and is itself a source of infection.

Unfortunately, this is not the end of the spread of the germ in the body.

The virus greedily seeks to annex the bone marrow - a kind of "command center ". From here, he will be able to send infected youthful blood cells to the front without any problems.

However, a wise body does not want to give up. A peculiar "arms race" begins, during which the immune forces of our kitten activate a lot of mechanisms aimed at eliminating the enemy.

Indeed, most animals fight viral load shortly after the virus has entered the marrow. Then we also have a winning case!

The body not only got rid of the virus from the blood, but also completely eliminated it.

As a reward, there is a development of a very strong immunity to protect against infection, which means that such individuals are in the VIP group = very low risk of disease. Again, the cat ends up healthy.

Bone marrow infection

However, it may be that after a 'siege' lasting about 3 weeks, the virus decides to get the fortress at all costs.

His plan is a real strategic artistry: the offensive is to invade the bone marrow and penetrate the precursors of individual blood cells.

It defensively integrates its genetic material into the genome of the host cells.

The cat's body has 2 options: either it will kill its own cells and their contents, which in light of the severity of expansion may be a shot in the knee (there will be huge losses), or it will leave the cells alone, which is a win-win situation for the virus - now it can roam freely around the body and shamelessly produce new generations of germs.

And so the virus massively infects the newly produced granulocytes and platelets.

A large-scale, strong viremia begins, accompanied by the involvement of the lymphoid tissue (hence the other name of the disease - lymphocytic leukemia) and salivary glands.

Malicious germs ruthlessly plan the future for their "offspring" - after all, they must somehow infect subsequent hosts and this is where saliva will be great. 1 ml of cat saliva is present over a million virus particles!

Some lucky cats may be suppressed even now after the marrow is occupied.

You have to hurry because the longer it lasts, the less likely it is.

However, it will not do without losses

The organism of a pet that has already had a bone marrow infection is not able to eliminate the virus, because it insidiously integrates its genetic material into the stem cells (these are bone marrow stem cells).

At this point, the so-called latent infection.

These cats do not produce active virus particles; the germ is somewhat "dormant" - waiting for favorable conditions (such as. weakened immunity, stress, pregnancy), when it is activated and attacks again.

This cat is clinically healthy - it has no symptoms, but diagnostic tests for FeLV are negative.

However, it is a kind of "delay bomb" that can explode at any moment. However, it does not always explode.

It happens - though extremely rare - that for some reason the disease is eliminated and the virus is completely eliminated.

Sometimes the virus remains dormant throughout the cat's life, and leukemia never develops, and other cats are never infected.

Such cats are referred to as healthy vectors.

Dormant FeLV activation

What happens when the virus is activated, however?

Then the aggressive and enraged germ reappears in the blood (this time it stays here forever) - this is the so-called. persistent viremia.

Such animals are already becoming a kind of machinery for reproducing and spreading the pathogen.

If that was not enough, there is a whole range of clinical symptoms and such kittens are officially considered to have leukemia.

The clinical picture of the disease may not appear until several years, however, the survival rate of cats from the diagnosis of the disease is usually up to 3 years.

Signs of leukemia in cats

Signs of leukemia in cats

What does the landscape look like after the battle in our purring friend?

Unfortunately, it is a real fire site with a great variety of forms and a variety of symptoms of the disease.

This is due to the nature of the virus (oncogenicity), its action (effects on the immune system), as well as the habitat (bone marrow and its cells).

Thus, we can deal with other clinical symptoms and accompanying disease entities.

The risk of developing neoplasms

Feline leukemia virus causes oncogenic effects.

Infection FeLV most often it is accompanied by the development of lymphomas (more about lymphoma can be found in the article "Lymphoma in a cat. Symptoms and prognosis ")

But this is not the entire repertoire of our infamous hero. It contributes to the development of leukemia and other tumors of the haematopoietic system. Growth is also noted in sick cats osteochondritis, olfactory neuromas or keratinized skin tumors.

Tumors of the haematopoietic system (myeloproliferative diseases)

  • Leukemia. Clinical symptoms are due to the deficiency of normal blood cells. Therefore, most often acute myeloid leukemias are accompanied by anemia, sepsis, hepatomegaly with accompanying jaundice and spleen enlargement. Diagnosis should be based on total blood counts and bone marrow examination. Unfortunately, a kitten with myeloid leukemia has a poor prognosis.
  • Myelofibrosis - permanent stimulation of the bone marrow by the virus leads to bone marrow fibrosis and increased production of cancer cells. In the diagnosis, the most important value is the examination of the material collected with the use of a biopsy.
  • Fibrosarcomas (fibrosarcoma). Their rapid growth is characteristic of them. Scattered nodules appear in the skin and subcutaneous tissue, metastasizing to the lungs and other organs. But be careful! These tumors should not be confused with feline fibrosarcomas (FeLV has no effect on their development).

Other tumors

  • Fibro-chondomas - in the form of cartilaginous growths on the bone surface. Usually mild, but due to their location (sometimes they are located near the spine), they can cause severe disease symptoms
  • Spontaneous olfactory neuromas embryonic - malignant and aggressive tumors of the epithelium of the nose and throat with a tendency to metastasize
  • Cutaneous horn - benign growth of keratinocytes. The virus's contribution to its development is still unclear
  • Melanoma of the iris - the still controversial role of FeLV in its pathogenesis

Hematological disorders not related to neoplasia

Due to the suppressive effect of the virus on the bone marrow, haematological disorders are often noted.

Anemia and related to it:

  • somnolence,
  • lack of appetite,
  • apathy,
  • pallor of the mucous membranes,
  • jaundice,
  • dehydration,
  • enlargement of the spleen.

Often the disease is complicated by a secondary infection Mycoplasma haemofelis, which further aggravates the symptoms of anemia.

Platelets abnormalities - may contribute to the occurrence of excessive bleeding in cats.

Neutropenia responding to treatment with glucocorticoids. It usually appears cyclically and consists in the fact that there are too few neutrophils in the blood.

Due to the weakening of the "first line of defense" in cats with neutropenia, the following is observed:

  • recurring fever,
  • chronic bacterial infections,
  • chronic gingivitis with symptoms of hyperemia and purulent exudate.

Syndrome panleukopenia-like. It resembles panleukopenia, characteristic of cats, but is accompanied by anemia in cats with FeLV.

The clinical picture is typical of enteritis.

Weakening of the immune system

The retrovirus that causes feline leukemia significantly weakens the feline immune system.

As in people infected with HIV, secondary bacterial, viral or fungal infections are very common.

Such a kitten becomes defenseless even against common pathogens, with which the body of a healthy cat would be great to deal with.

Skin diseases

They are often related to immunosuppression.

Traumatic wounds, common allergy or even external parasites predispose to the development of secondary infections, the appearance of abscesses, inflammations of the external auditory canal or miliary dermatitis.

Immunological diseases

  1. Immune haemolytic anemia.
  2. Glomerulonephritis.
  3. Uveitis with the deposition of immune complexes in the iris and ciliary body.
  4. Polyarthritis.

Other syndromes

  1. FeLV-associated enteritis - symptoms most commonly include bloody diarrhea, vomiting, mouth ulcers, gingivitis, loss of appetite, and weight loss. Sometimes there are nonspecific symptoms in the form of rhinitis, shortness of breath and apathy.
  2. Feline acquired immunodeficiency syndrome associated with FeLV - and this may include difficult-to-treat diarrhea (as a result of inflammation of the small intestine and colon), as well as non-specific opportunistic infections.
  3. Reproductive disorders - in pregnant cats, fetal resorption, miscarriage and death of embryos are possible. At the end of pregnancy, abortions often occur with the excretion of properly developed fetuses. It is often accompanied by inflammation of the uterus due to bacterial infections
  4. Poor kitten syndrome. Some kittens are resistant to infection, but most develop viremia and then die early - most often in the first 2 weeks of life. It is accompanied by anorexia, dehydration, hypothermia and thymus atrophy.
  5. Neurological disorders - pupil dilation and asymmetry, blindness, Horner's syndrome, vocalization, hyperesthesia, paresis, urinary incontinence - these are just some of the symptoms that can appear as a result of the virus.
  6. Liver diseases - jaundice, hepatitis or its degeneration.

You can see what advanced symptoms of cat leukemia may look like in the video below

feline leukemia virus
Watch this video on YouTube

Diagnosis of feline leukemia

Feline viral leukemia diagnosis

The most effective form of fighting leukemia is its early monitoring.

Its purpose is not only to detect cats infected with the virus, but also to inhibit the spread of the virus in the cat population.

The main diagnostic methods used in clinical settings are:

  • direct immunofluorescence (FA) test,
  • ELISA test,
  • immunochromatographic techniques (ICGA).

The main material for testing is blood. It is also possible to detect virus antigens in tears and saliva, but there is a higher risk of false negative results.

When is the best time to have a blood test for leukemia?

  1. At least once in my life in all cats. Regardless of where the kitten comes from, what is his background and whether he was vaccinated against leukemia. I know from experience that many cats are vaccinated against this disease and have never been vaccinated leukemia test. Unfortunately, this disease can occur regardless of previously performed tests and vaccinations.
  2. If you observe any symptoms in your cat suggestive of the disease, and when abnormalities related to FeLV infections (hematological disorders, cancer, immunosuppression, frequent and recurrent infections) have been found.
  3. If you already have a kitten at home and you want to adopt another one. Whenever a new cat is brought home (regardless of its age), a FeLV test should be performed. Remember that leukemia is an infectious disease!
  4. After contact with other cats, especially if they have not been vaccinated - such a test is best done after approx. 28 days after possible exposure to the pathogen or perform them twice.

My cat is FeLV positive. What's next?

Felv positive in the cat

A positive cat leukemia test is not yet a sentence.

Confirmatory tests only detect infection with the virus (that is, its presence in the blood), not disease!

In the absence of clinical signs of leukemia, cats with FeLV can live for many years.

Even if the infection is accompanied by any symptoms, other factors may cause the infection.

Additionally, keep in mind that none of the tests are 100% reliable. Therefore, their results should be interpreted in relation to the animal's current health status and possible exposure to the pathogen. Sometimes it is also worth repeating the test.

In order to proceed accordingly when detecting FeLV in a cat, let us consider several hypothetical situations.

  1. The test was performed on one of the many domestic cats. We already know how the leukemia virus spreads in the cat population, we also know that some individuals can acquire immunity after a single contact with it. What to do to protect the rest of our kinsmen?
  • The first and fundamental thing - we test all cats for FeLV. The best method of preventing the spread of the virus is to completely isolate infected individuals without contact with healthy ones. And even acquired immunity in the rest of the world doesn't last forever. The ability to neutralize the virus is not sustained throughout life - over time, viremia can also develop in cats deemed immune to the infection. Remember that such a kitten under no circumstances should contact other cats, even those not from our cattery.
  • Healthy cats should be vaccinate against leukemia. However, also here it should be remembered that in such a situation vaccination does not guarantee full protection against infection.
  • After several months or years, when infected cats are naturally removed from the cattery, the remaining cats are considered resistant to infection.
  1. A positive FeLV test was performed at our only client.
  • Infected animal should only be at home. Cats with diagnosed FeLV should not be allowed to leave the house not only because it poses a risk to other cats. Remember that in the course of FelV immunosuppression occurs, and this puts our cat in the face of a huge probability of various infections or diseases.
  • Nutrition - it is safest to give food that is specially balanced and highly nutritious. You can trust the producers of commercial pet food in this matter. Avoid using raw meat, eggs or pasteurized milk (risk of transmitting bacteria or parasites with food).
  • Control tests in a veterinary clinic - at least once every six months, sometimes more often.
  • Prevention against internal, external and cardiac parasites, as well as prophylactic vaccinations against infectious diseases.
  • Sterilization or castration to avoid heat stress.

Treatment of cat leukemia

Leukemia in a cat, antiviral treatment

Treatment of cat leukemia

Scientists have been puzzling over the development of an effective method of treating leukemia in cats for years.

Unfortunately - so far there is no such method of therapy that would eliminate the virus from the body.

Of course, antiviral preparations were introduced into treatment, but for various reasons, they did not fulfill their role.

An effective antiviral drug is one that inhibits replication of the virus and stimulates the immune system to fight the pathogen. In addition, it should be as toxic as possible, relatively cheap and in an oral form (it must be administered for the rest of the patient's life). Unfortunately, such a drug has not been developed.

Some hopes were pinned on zidovudine (AZT), which is quite effective in inhibiting the replication of the virus, but due to its side effects (strong bone marrow suppression), its use is limited only to coexisting acute gingivitis or neurological disorders, and then the patient's condition should be carefully monitored and blood counts checked.

Other drugs like didanosine, zalcitabine, ribavirin, foscarnet if suramin either they show a relatively high toxicity, or their use causes a strong suppression of the bone marrow, therefore clinicians very rarely use them.

Despite the use of these drugs in human medicine (e.g. treatment of HIV infections in humans), their efficacy against FeLV in natural infections of cats has not been proven.

Leukemia in the cat, immunomodulating treatment

Leukemia immunomodulating therapy is by administration interferon, which has immunomodulatory and antiviral effects.

Several types of interferons are available, the most common of which is human interferon α and recombinant feline interferon ω (preparation Virbagen).

Cats undergoing interferon therapy are characterized longer survival and lower severity of disease symptoms.

Fighting diseases accompanying FeLV infection

Treatment of leukemia mainly involves combating the secondary infections that accompany it.

Treatment of infected cats does not differ from that of uninfected cats, however, in the former it usually takes longer.

Although it usually takes approx. 3 years, but in reality - with proper recommendations - infected individuals may live longer and die at an older age for reasons completely unrelated to FeLV.

To prevent infection with feline leukemia

The first and fundamental issue in preventing the spread of the feline leukemia virus is monitoring, especially in the case of breeding or large clusters of cats.

Regular testing to identify infected individuals and their separation is a more effective form of disease control than vaccination alone.

Vaccination of leukemia in cats

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Kittens should be vaccinated for leukemia twice at 3-week intervals, starting from 8-9 weeks of age.

Further booster doses are given one year after the second vaccination, and every year thereafter.

This type of procedure is recommended for outgoing cats that have access to the virus in the environment.

Leukemia vaccination is inherently associated with the risk of developing dangerous and fatal consequences post-vaccination sarcomas.

The frequency of these menacing tumors is so high that it has been developed special injection scheme.

An injection into the left pelvic limb is recommended.


In the event of a tumor, the leg may be amputated as a last resort, thus saving the animal's life.

The decision to vaccinate should be taken carefully, having the actual exposure of the cat to infection.

Is there anything to worry about?

How to prevent disease?

Feline viral leukemia is a highly contagious disease that reaps results among our purring brethren.

The fight against the virus is often doomed to failure in advance, and the course of the disease itself can be exhausting not only for the patient, but also for the owners themselves.

Therefore, let's not forget about it during the kitten's "checkups" at the clinic.

Let's suggest the doctor to take a test, let's talk about the risks and possibilities of prevention FeLV leukemia.

Let's do everything so that our furry friend will never be a training ground for action feline leukemia virus.

You have viral related questions leukemia in a cat? Or maybe your cat is at risk and you want to learn more about prevention? Now add a comment under the article, I will write back as soon as possible.

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