Feline Leukemia Virus (FeLV)

Feline leukemia virus (FeLV) is caused by a circular shaped RNA retrovirus (in a group called Oncornavirus). This virus is capable of lying dormant and cause disease slowly. FeLV causes immunosupression which means the body’s immunity system gets compromised and in time collapses. This leads to weakened immunity system and the ability to fight diseases and infections declines. FeLV is also known to cause anemia, leukemia and certain types of cancer.

The virus cannot survive in the environment for long and can be killed easily by common disinfectants.

The primary mode of transmission is by direct contact with infected saliva. Cat bites, grooming (involving saliva) between cats, blood transfusions, from a pregnant mother to her kittens.

Outdoor cats are at a high risk as compared to indoor cats as they have a greater risk of exposure. Once a cat has been infected with FeLV, it will remain infected with the virus for life (the infection is permanent). A cats body becomes incapable of developing a normal immunity response. Though infected, a cat will remain healthy for years. Gradually, as the effect of virus progresses, the immune system is completely destroyed. FIV infects the cells of the immune system (white blood cells [WBC]) mainly lymphocytes. The virus damages or kills the cells or may alter their normal function.

The virus damages or kills the cells or may alter their normal function. Because of its slow progression the symptoms may not show for years after the infection has occurred, the cats immunity system is weakened and gradually declines. Collapsing immunity makes the cats susceptible to other secondary infections which follow. During the first few weeks of the infection, the cats defenses build a response that will not eliminate the virus – the virus keeps multiplying at a very low level. The signs are so mild they usually go unnoticed, the first diagnosis usually happens between three to five years (after the cat was infected) when there is increased virus replication within the cats body. This leads to progressive damage to the immune system.

During the first few weeks of infection, the cats defenses do build up, but are unable to completely ward of the virus. FeLV keeps multiplying at a very slow level. Clinical signs as so mild that it may go unnoticed. The first diagnosis happens between 3 to 5 years post getting infected.

FeLV is a slow progressing disease and a cat will not show any symptoms of being infected. A declined and weakened immunity makes the cat susceptible to other secondary infections and diseases.


FeLV is caused by retrovirus. It can be spread only in a few circumstances such as cat bites from infected cat, wounds, pregnant queens to her kittens, mutual grooming and in rare cases infected blood transfusions.

Clinical Signs & Symptoms

FeLV causes disease through immunosuppression (weakened immunity system which is susceptible to secondary infections) and may not show the symptoms for years. The normal immune functions of the cat are altered, the cat is prone to other diseases and infections. There are no specific signs with this infection. Some of the signs to watch for are:
› Lethargy
› Pyrexia (Fever)
› Anorexia (Loss of Appetite)
› Alopecia (Hair Loss)
› Diarrhea (Loose stools)
› Pollakiuria (Frequent urination)
› Anemia
› lymphadenitis (swelling of lymph nodes)
› Weight loss
› Gingivitis (Inflammation of the gums)
› Stomatitis (Inflammation of the mouth)
› Skin diseases
› Recurrent ocular discharges
› Recurrent nasal discharges
› Gastrointestinal tract diseases
› Respiratory diseases
› Uveitis (inflammation of the inner pigmented structure of the eye)
› Conjunctivitis (Inflammation of the eye)
› Haemoplasma infections
› Lymphoma
› Central nervous system (CNS) signs
› Seizures
› Abscess
› Jaundice

(Note: minor infections will keep occurring over time and they will take a longer time to heal. Wounds will take longer than usual to heal)


FeLV can be difficult to diagnose as it can mimic symptoms of other known diseases like Feline Infectious Peritonitis (FIP), Feline Immunodeficiency Virus (FIV), Histoplasmosis, Feline Ehrlichiosis, Feline Infectious Anemia etc.

Veterinarians will require a complete history of your cat which includes medical history, vaccination records, existing health concerns, current and previous medications, onset of symptoms, diet and exercise routine and any information which can help in establishing a correct diagnosis. Diagnosis is done with a combination of tests. These include routine lab examinations and special tests which can detect the presence of the virus. They are:

› Physical examination (includes checking for paleness in the gums, lymph node size)
› Complete Blood Count (CBC)
› Biochemical profile
› ELISA test (Enzyme-Linked Immunosorbent Assay)
› PCR test (Polymerase Chain Reaction)
› IFA Test (Immunofluorescent assay)


There is no cure for FeLV. FeLV infected cats are known to survive for up-to three years. The treatments associated with FeLV are to prevent further spread of the disease to other cats and because a cats immune response is compromised, it is prone to secondary infections which may cause health issues. Your veterinarian may advise you of the supportive treatments your cat should get. They are:
› FeLV Vaccination
› Antibiotic Medications (for secondary infections)
› Fluid therapy (for dehydration)
› Treatment for Gingivitis and Stomatitis
› Restricting the FeLV infected cats movements (keeping them indoors, away from non-infected cats)
› Blood transfusions (in-case of severe anemia)
› Chemotherapy and associated drugs
› Timely diagnosis and treatment of secondary infections
› Healthy nutritional diet


Vaccination is the single most effective way to prevent the disease. Keep in mind FIV has a global distribution – it is present everyehere. Please consult your veterinarian and ways to prevent your cat from getting infected and talk about the vaccine schedule.

Home Care

FeLV causes immunosupression. Your cat is at a higher risk of getting secondary infections.

› Vaccinating your cat. Choice is generally nasal vaccines as they work faster.

Once diagnosis confirms FIV:

› A well planned, nutritious diet is necessary in such conditions (avoid raw foods). Routine and regular checkups to access the progress, further tests may be advised.
› Do not allow your pet to roam freely. This works two ways, firstly if the pet is infected, it greatly reduces the chances of risk of exposure to other pets and humans and secondly in-case of a healthy pet, it reduces the chances of contracting the infection. Do not allow your pet to go through garbage bins, water sources, fecal infected areas.
› DO NOT BREED cats diagnosed with this disease.

Related posts

Leave a Reply

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