Feline Leukemia – The Facts

What is FeLV (Feline Leukemia)?

Feline Leukemia Virus (FeLV) is a virus that infects only cats and is fairly common. FeLV depresses the immune system and may lead to persistent infection in a cat. FeLV is an predominantly a cause of anemia in cats. It additionally can cause cancers of several types. It is found worldwide. It is transmitted through the exchange of bodily fluids between cats when fighting, grooming, sharing eating stations, and litter boxes. There is no treatment to eliminate the FeLV virus from the body once infected, and thus the disease is ultimately fatal.hypodermic needle and medicine

How Does a Cat Contract Feline Leukemia?

The most common way a feline can contract the disease is through saliva and casual contact with an infected cat such as biting, mutual grooming, sharing bowls, and even touching noses. Since this disease is highly contagious between cats, it is important to completely isolate new cats of unknown viral status. It is also important for humans to wash their hands when handling multiple cats. Kittens are more susceptible to FeLV. Cats who go into the our0of-doors are at greater risk of exposure. The virus can also be transmitted from mother to kittens. Kittens can become infected during fetal development or during the first days of life as their mothers nurse and care for them.

How Does FeLV Cause Disease in its Victims?

The Feline Leukemia Virus can cause bone marrow suppression. As one of the functions of bone marrow is to produce the cells of the immune system that fight off infection, this disease can result in a suppressed immune system. The immune system normally protects the cat from common infectious agents such as bacteria and viruses, that do not generally cause disease in healthy cats. However, if a cat’s immune system is weakened, as with FeLV, these same organisms can cause disease. This is known as secondary or opportunistic infection. Although the disease only affects cats, it is recommended that immunocompromised people such as chemotherapy patients and AIDS patients, not reside with FeLV + cats because these cats are they can infect these patients that are immunocompromised. This viral disease is also associated with the development of certain types of cancer such as lymphoma and leukemia, in affected cats.

What are the Signs?

  • Oral Signs

A cat may develop pale gums and/or a yellow color in the mouth. Some cats also develop stomatitis, meaning their gums become very inflamed and ulcerated.

  • Respiratory Difficulties

It’s easy to spot the warning signs of feline leukemia when the virus is settling in the chest. The cat will cough and have other signs of respiratory problems with gagging on phlegm that is being produced. Wheezing and a runny nose or eyes is also common.

  • Stomach Problems

When the virus settles in the abdomen, a cat may experience bloating and other signs of abdominal problems. The cat will also experience vomiting and/or frequent diarrhea which is usually accompanied by a lack of appetite.

  • Weight Loss

Feline weight loss is common when infected with the virus and appetite changes in a cat are always a reason for concern. In the case of FeLV these changes in eating habits are often the first symptom of the virus.

  • Lethargy and Weakness

Multi-centric (entire body) leukemia can show itself in several ways. Typically, malignant tumors begin to grow in various parts of the body. This causes the immune system to stop working and the cat’s overall health begins to deteriorate. She may show signs of listlessness, sleepiness or personality changes.

Associated Medical Conditions

As a cat’s immune system weakens, other symptoms you will see can include enlarged lymph nodes and an unhealthy appearance to the cat’s skin and coat. Your cat will become susceptible to other conditions which can include:

  • Infections of the bladder, respiratory system and skin, among other systems
  • Infections that are chronic and resistant to treatment
  • Fever
  • Sterility

Recognize the Final Stages of Feline Leukemia

In the final stages of FeLV, the cat’s health will be severely compromised by the infection. This leaves it open to developing other diseases and disorders not related to FeLV. With any of the following symptoms, there is a good chance the feline may be in the final stages of FeLV:

  • Persistent infections, such as in the respiratory system, ears and in the mouth and gums
  • Inflammations in the eyes
  • Weight loss that does not improve and no interest in eating
  • Constant diarrhea
  • Difficulty in mobility
  • Extreme lethargy
  • Bodily tumors and cancer, particularly Lymphoma and Fibrosarcoma
  • Seizures
  • Overall changes in his behavior

Not every cat that becomes infected with FeLV develops clinical signs or long-term complications associated with the virus. The immune system of some cats can eliminate the infection before the cat becomes sick. In other cats, the virus can “hide” in the bone marrow, where it is difficult to detect until it begins to cause problems later in life. Other cats become carriers of the disease or experience various illnesses and immune suppression before eventually dying of FeLV-associated complications.

cat at veterinarianHow is a Cat Tested?

A simple in-house blood test, or “snap” test have been developed to detect the presence of the FeLV. In general, these tests are very reliable, with almost 100% accuracy.

In some situations, a second blood test is needed for confirmation at a veterinarian office. If a cat tests positive for the virus, it could mean that the cat has FeLV or a false positive showed in the results. A positive test should be confirmed by an IFA test, which can be done at a full-service vet clinic.

If the IFA test is negative, it could mean that the cat is:

A) not infected with FeLV at all.

B) recently infected (up to 30 days ago) but won’t test positive yet, in which case a repeat IFA test should be done again approximately four weeks later to confirm.

Protection and Possible Outcomes for a Patient

FeLV positive cats must be kept indoors away from unaffected cats so they don’t spread the disease to other cats.  They should be spayed/neutered, provided with good nutrition, avoid raw diets, and need regular visits to their veterinarian. With proper care many FeLV cats can live months to years in good health.

Cats infected with FeLV have 4 different possible outcomes.cat at veterinarian office

  1. A cat may succumb to the infection and develop FeLV associated diseases. The development of FeLV associated diseases such as bone marrow suppression or cancer poorly affects the cat’s prognosis.
  2. A cat may overcome the virus but the viral “DNA” is incorporated into the cat’s own DNA; these cats may or may not develop illness at some point in their lifetime. Those cats that are infected and have no clinical signs may remain asymptomatic for months to years or for life. These cats should still be considered contagious to other cats.
  3. A cat may completely eliminate the virus from their system
  4. A cat’s system could be confined / localized the virus to a small region of the body, such as a mammary gland. This is rare.

As it helps to keep cats  INDOORS, if they are also outdoors cats, make sure to have them tested and vaccinated.

Vaccinations are highly recommended for kittens and also for adult cats determined to be at risk (i.e. cats that go outdoors or encounter new cats that have not been viral tested).  Vaccinations will NOT interfere with testing for the disease.

Remember to isolate and test kittens or new pets, for FeLV, before allowing them to come into contact with your existing pets.


Feline Leukemia Virus (FELV) is a relatively common viral disease of cats. Some cats acquire this infection at a very young age by being born to an FELV-infected female cat, others contract this disease through direct contact with bodily fluids from another infected cat. Most cats with FELV lead full, normal lives, but these cats do have special environmental and health requirements and are susceptible to some health consequences once infected.

Leave a Reply

Your email address will not be published. Required fields are marked *