Feline Leukaemia in Cats: How It Spreads, Which Cats Are at Risk, and When to Vaccinate

Feline leukaemia vaccination can reduce a cat’s risk of infection with feline leukaemia virus (FeLV), a virus spread mainly through close contact with infected cats. Progressive FeLV infection can weaken the immune system and contribute to serious illness, although the course of infection varies between cats. 

This guide explains how feline leukaemia virus, usually shortened to FeLV, spreads between cats, which cats face the highest risk, why testing normally comes before vaccination, and what living with an FeLV-positive cat looks like day to day.

What Is Feline Leukaemia Virus?

Feline leukaemia virus is a virus that affects cats and suppresses the immune system, leaving affected cats more vulnerable to infections and certain other illnesses over time. It is one of the more significant viral diseases veterinarians in Malaysia see in cats with outdoor access or contact with other cats.

FeLV is specific to cats and does not affect dogs or people. Within the cat population, however, it can pass between animals through several routes, which is why our veterinarians at STARLiGHT Veterinary Hospital are often asked about it during wellness visits.

How Feline Leukaemia Spreads Between Cats

FeLV is passed between cats through close and prolonged contact rather than brief or casual contact. The main routes include:

Main Transmission Routes

• Mutual grooming between cats that live together or interact regularly.
• Shared food and water bowls or litter trays used by an infected cat.
• Bite wounds, which can transmit a higher viral load than grooming or shared bowls.
• From an infected mother cat to her kittens, either before birth or through nursing.
• Prolonged close contact in multi-cat households or colonies where cats interact daily.

Brief contact, such as cats meeting once through a fence or at a distance, carries a much lower transmission risk than the sustained contact described above. This is one reason indoor cats with no contact with other cats face a lower overall risk than cats with regular outdoor access.

Which Cats Are Most at Risk

Higher-Risk Cats

Cats that spend time outdoors unsupervised, live in multi-cat households of uncertain FeLV status, or have regular contact with cats whose vaccination and testing history is unknown face the highest exposure risk. Kittens are generally considered more susceptible to infection than adult cats if exposed.

Lower-Risk Cats

Cats that live entirely indoors with no contact with other cats face a much lower risk, though it is not necessarily zero if there is any chance of contact with an unknown cat, for example through an open window or an accidental escape. 

Our veterinarians can help assess your cat’s individual risk based on their specific lifestyle.

Why Testing Comes Before Vaccination

Our veterinarians normally test a cat’s FeLV status before the first vaccine dose, since the vaccine is intended for cats that are not already infected. Testing is a simple in-clinic procedure using a small blood sample, and results are typically available during the same visit.

If a cat tests positive, vaccination is not the next step, and our veterinarians will instead discuss what a positive result means for that cat’s ongoing care. You can read more about our on-site diagnostic and laboratory testing on our pet diagnostic service page.

Living with an FeLV-Positive Cat

There is no cure once a cat is infected with FeLV, which is a factual statement about the virus rather than a claim about any particular treatment outcome. Many FeLV-positive cats can still live a comfortable life for a meaningful period with appropriate monitoring and care from their veterinarian.

Cats confirmed positive are usually kept separate from FeLV-negative cats in the household to prevent transmission, and regular veterinary check-ups become more important to monitor their health over time. Our team can talk through a monitoring plan suited to an individual cat’s circumstances.

Vaccination Recommendations for Cats at Risk

Feline leukaemia vaccination is recommended for cats that go outdoors, live in multi-cat households, or have any contact with cats of unknown status. It sits alongside the core vaccines covered on our cat and dog vaccination services.

Our veterinarians will talk through whether your cat’s circumstances call for FeLV vaccination as part of a standard wellness consultation. This is an individual assessment rather than a blanket recommendation applied to every cat.

Multi-Cat Households and New Cat Introductions

Testing every cat in a multi-cat household is a sensible step before introducing a new cat, since it confirms the FeLV status of both the existing cats and the newcomer. This matters most where cats will share close living space, food bowls, or litter trays over a prolonged period.

A new cat of unknown history is generally kept separate from resident cats until testing is complete. Our veterinarians can advise on a suitable introduction timeline once test results are known.

What to Expect After a Feline Leukaemia Vaccination

Most cats tolerate the feline leukaemia vaccine well, and any reaction is typically mild, such as brief tenderness at the injection site or a quieter day afterwards. Our veterinarians will explain what to watch for after your cat’s appointment.

Keeping your cat calm and allowing them to rest for the remainder of the day after vaccination is a sensible general precaution. If anything about your cat’s behaviour after vaccination concerns you, contact our hospital and our team will advise you on next steps.

Booking a Feline Leukaemia Test or Vaccination in Ampang Jaya

Whether your cat is due for a first FeLV test, a vaccination decision, or simply a wellness check to talk through their individual risk, our veterinarians can cover this at a routine appointment. There is no need to wait for symptoms before booking a test, since this is preventive rather than emergency care.

If you would like to test your cat for FeLV status or discuss whether vaccination is appropriate, our team can help. You can reach us through our contact page, and appointments can also be scheduled through the Pet Universe App.

Frequently Asked Questions