Feline Leukaemia Virus (FeLV)

Feline Leukaemia virus (FeLV)
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Filed under Cats, Elderly Cats, Kittens.
Image credit: Image from bishopranch.blogspot.com

FeLV is an infectious viral disease that affects cats. This virus, as with Feline Immunodeficiency Virus (FIV), suppresses an infected cat’s immune system. Without a healthy immune system, cats are significantly more prone to bacterial, chlamidial, mycoplasmal and other viral infections and will ultimately lead to either spontaneous death or euthanasia of the infected animal. FeLV also increases the chances of carrier cats getting certain deadly cancers.

There is currently no effective cure for this disease, just prevention.


Any cat disease can be a result of FeLV. Symptoms in infected cats can appear months or even years after becoming infected. A wide range of clinical signs is seen incl. any or a combination of the following:

  • Loss of appetite
  • Poor coat condition
  • Recurring infections of the skin intestines, eyes, bladder and respiratory tract
  • Oral disease
  • Seizures
  • Swollen lymph nodes
  • Skin lesions
  • Fatigue
  • Fever
  • Weight loss

At home, a sick cat is usually identified by poor or no appetite, poor hair coat and weight loss.


Feline Leukaemia Virus is transmitted from an infected cat to a susceptible cat via saliva and nasal discharges. This mostly happens through catfights. Male cats defending their territory and wild stray cat populations are the main sources of infection. FeLV can also be transmitted between cats by sharing litter boxes or food and water bowls or even grooming. Kittens from infected mothers can also be born with this disease.


  • Do not introduce a stray/adopted cat into your household without having him/her tested by your family veterinarian first.
  • Sterilisation of young cats to discourage roaming.
  • FeLV vaccinations.
  • All outdoor non-vaccinated cats should be periodically tested for FeLV and FIV so proper steps can be taken to minimise exposure to the general population.

My cat has been diagnosed with FeLV. Now what?

The long-term outcome will depend on whether your cat is healthy or not at the time of the diagnosis. Diseased cats at this time carry a poorer long- and short-term prognosis in that the outcome of their immediate disease(s) is questionable. The same way, possible (very likely) future diseases (even if generally not serious to non-FeLV patients) might have additional treatment difficulties. Infected cats will be very prone to a variety of feline diseases. A young diagnosed cat is very likely to die or be euthanised from a complicated disease process secondary to Leukaemia virus.

Because of this and the infectious nature to other cats, the decision to treat instead of euthanasia should be taken very seriously.

With healthy or recovering cats, the first thing to do is to isolate infected patients by keeping them indoors away from other cats. As mentioned above, these patients will be more prone to diseases. A sick FeLV cat should be presented to your family veterinarian as soon as possible for diagnoses and treatment. Symptomatic and sometimes supportive treatment can be given as necessary. Where isolation is impossible or impractical or where supportive treatment becomes ineffective, euthanasia is strongly recommended.

Apart from isolation from other cats, additional measures include a good-quality premium cat food, strict litter box hygiene and yearly testing of possible in-contact household cats. In-contact cats should also be vaccinated. Because of the insidious nature of this disease, it is also strongly recommended to present infected cats, even if seemingly healthy, for a routine veterinary check-up every six months.

Feline Leukaemia Virus vaccination protocol (healthy, non-affected cats)

  • Only healthy cats should be vaccinated.
  • Cats nine weeks of age or older are vaccinated once with a primary booster vaccination given 15 to 21 days later.
  • Boosters are then given annually with or without routine annual vaccinations.
  • Kittens can also be protected by vaccination of the mother prior to mating.
  • To ensure the efficiency of the vaccine, it is strongly recommended that cats are tested for the FeLV virus before vaccinating them. This can be quickly done with an in-house snap test during the vaccination consult at our veterinary hospital.
About the author
About the author
Renier is a qualified, experienced companion animal veterinarian whose main interests are animal health and strengthening pet-owner relationships.
View all posts by Dr Renier Delport (BVSc.)

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