Many cat owners have heard of “leukosis” but do not know what the term is. No wonder: When we talk about “leukosis”, what is usually meant is a leukemia virus infection in the cat. Although this infection is quite widespread, it can develop very differently depending on the animal. In the following, you will learn more about “cat leukosis” and how you can protect your cat from it.

“Leukosis” and the feline leukemia virus

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Doctors use “leukosis” to describe a tumor in the white blood cells. In German-speaking countries, many pet owners and veterinarians use the term for malignant disease in cats that is triggered by the feline leukemia virus (FeLV). White blood cell tumors are just one of many possible symptoms that can occur after infection.

How contagious is FeLV?

Cats can transmit the virus through saliva, tears, or nasal secretions. This can happen with every closer contact between two cats – from the welcoming sniff to cleaning. The viruses can only survive for a few minutes outside the cat’s body. Nevertheless, drinking bowls or toys used at the same time carry a risk of infection. FeLV is not transferable to humans (no so-called zoonosis).

The course of a FeLV infection

The good news right at the beginning: If the feline leukemia virus is found in the blood count of a cat, this is not a death sentence! In fact, many outdoorsmen come into contact with it without falling ill. Infection with FeLV can take various forms:

The immune system wins

Healthy, adult cats often survive a leukosis infection unscathed and are subsequently immune to the FeLV virus.

A latent infection develops

In some cats, the immune system is less powerful. The virus can therefore penetrate as far as the stem cells, but can no longer be detected in a blood test. The affected cat thus continues to carry hidden (latent) FeLV within itself, but cannot infect any conspecifics. But another basically harmless illness or stress can strengthen the virus again, so that the disease breaks out. Latent virus carriers that do not develop leukemia have a good prognosis.

The immune system is subject to progressive infection

We speak of a permanent infection if the viruses are constantly detectable in the body and multiply. In these cats, “leukosis” or the diseases associated with FeLV usually breaks out months to years later.

Symptoms of “cat leukosis”

Cats that have been shown to be carrying FeLV have a weakened immune system. As a result, even under normal circumstances, harmless diseases such as a slight infection of the velvet paw can become dangerous. The cats are generally ailing. The immune system can also turn against its own body and cause inflammation of the eyes, joints, or kidneys. If FeLV has broken out, anemia often occurs, so that the cat becomes noticeably weaker and eats less. Some cats develop eponymous tumors in the blood – as in leukemia – or solitary tumors in the liver, stomach, or kidneys.

“Leukosis Test” and Diagnosis

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Before a cat moves in with you, you should have it tested for the feline leukemia virus. This is usually a double test that also tests for the second important retrovirus, feline immunodeficiency (FIV). Such a test should also be carried out before a leukosis vaccination. False-positive results are possible – or the cat can successfully fight the infection. That is why another test is carried out a few weeks after a positive result. If this is also positive, the vet usually tests again around ten weeks later: If the virus can be detected in the blood again, it is a progressive infection.

What does a positive test result mean?

If the FeLV virus is permanently detectable in the blood of a cat, it sheds the virus. It should not have close contact with healthy conspecifics. If it doesn’t show any more symptoms, there are several things you can do to keep the disease at bay. Indoor cats who are less stressed and exposed to infection pressure from other cats have a better chance of long cat life. Regular vaccinations against cat disease and cat flu are also important. Feed them good quality and rich in protein to strengthen the immune system. Additional vitamins are not necessary.

How common is “leukosis”?

The feline leukemia virus is relatively widespread. There are strong regional differences: In wild cats, depending on the region, between one and eight percent can be infected. However, it is believed that over 20 percent of all cats weakened by disease within a cat population also carry the FeL virus. Female cats are just as likely to be affected as males. Thanks to vaccination and education, the number of affected cats has been falling for years.

Preventing feline leukosis

Protect your cat from the feline leukemia virus by preventing contact with infected animals. The owners of affected animals are responsible: A cat with FeLV should no longer be given unlimited freedom of movement. A vaccination protects healthy outdoor animals.

Endangered: young cats and outdoor cats

Young cats up to the age of 16 weeks in particular quickly become infected with the feline leukemia virus. The older the cat gets, the less likely it is to become infected. However, this should not be taken lightly. An attacked immune system or many FeLV-positive cats in the immediate vicinity encourage infection.

Vaccination against FeLV

Especially young cats that are given free rein should receive a leukosis vaccination. This is not necessary for purely indoor cats without contact with infected cats. But be careful: a vaccination does not provide reliable protection in the event of constant contact with cats that excrete FeLV. For example, if two cats live in the same household, clean each other, or fight with each other. If you are older, you should discuss the benefits of vaccination with your veterinarian.

Therapy & costs

The symptoms or secondary diseases triggered by FeLV are very different. It is therefore not possible to make a general statement about the costs of leukosis therapy.

Modern FeLV therapy: interferon

Interferon is an immunotherapy drug that has a wide range of uses in human medicine. An interferon drug especially developed for dogs and cats can be used for FeLV: It can inhibit the virus from multiplying in the cat’s body and slow down the disease. In the final stage, however, it can no longer be used. Your vet will advise you individually.

Homeopathy for sick cats

Once the “leukosis” has broken out, homeopathic remedies can no longer influence the course. If you would like to support your cat palliative, clarify the administration of homeopathic remedies with your veterinarian beforehand.

Life expectancy in leukosis

If the first symptoms occur as a result of a FeLV infection, life expectancy can vary depending on the general condition. Some cats survive a few weeks, others can be by your side for years with a good quality of life.

Conclusion: Feline leukemia viruses are not a death sentence

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The disease does not actually break out in every cat infected with FeLV. Oftentimes, there are many symptom-free years before the cat shows symptoms. But then FeLV is usually fatal.