Feline Leukaemia Virus (FeLV)

Also called: FeLV

• Cats
• Infectious (viral)
• Young / Adult

FeLV is a viral infection (a retrovirus) that can suppress the immune system, cause anaemia and other blood disorders, and is the most common infectious cause of cancer in cats. It spreads through close, prolonged contact between cats (saliva, grooming, shared bowls, bite wounds, and mother to kittens). Unlike FIV, an effective vaccine exists. FeLV-related disease is often serious, though some infected cats live for years.

Signs to look for

• Often none early on
• Progressive deterioration or recurrent illness over time
• Weight loss and poor coat
• Pale gums (anaemia), lethargy, weakness
• Persistent fever
• Recurrent infections (skin, bladder, respiratory)

How a vet diagnoses it

Blood tests detecting FeLV antigen (point-of-care test), with confirmatory/follow-up testing (e.g. PCR) to distinguish progressive from regressive infection. All cats in a household should be tested if one is positive.

Treatment

No cure. Care focuses on keeping infected cats indoors and separated from uninfected cats, prompt treatment of secondary infections, good nutrition, and regular (often twice-yearly) veterinary checks. Vaccination is available and considered a core vaccine for kittens.

Monitoring at home

Red blood cell counts/anaemia, body weight, secondary infections, and overall condition with more frequent vet checks.

Who tends to get it

Kittens and young cats are most susceptible; outdoor and multi-cat-household cats are at higher risk. Australian context: FeLV is relatively uncommon in pet cats (around 1–2% of outdoor-access cats antigen-positive; confirmed progressive infection lower still).

Sources

• Cornell Feline Health Center — Feline Leukemia Virus
• VCA Animal Hospitals — FeLV Disease Complex