FeLV in cats: transmission, tests and care

A cat with FeLV may look healthy for a long time. Another is brought to the clinic after losing weight, eating less or developing repeated infections. You cannot tell them apart by appearance, and one positive screening test does not always tell the whole story.

FeLV is a serious infection, but the result alone cannot predict how the cat will fare or how long they will live. The next step is to understand which test was used, confirm the result when appropriate and plan prevention at home.

What is FeLV and what happens after exposure?

FeLV stands for feline leukemia virus. It is a retrovirus that infects cats. It does not infect people or dogs. Despite its name, not every infected cat develops leukemia. The virus can also be associated with anemia, immune suppression, lymphoma and other conditions.

After exposure, a cat’s immune system can respond in different ways. This helps explain why two cats exposed in the same home may have different test results and outcomes.

Response to exposure	What happens	What tests may show	Transmission to other cats
Abortive infection	The immune response controls the virus before it becomes established	Routine tests tend to remain negative	The cat does not shed the virus
Regressive infection	Viral material remains integrated into cells, but replication is controlled	Antigen may become undetectable; PCR may identify proviral DNA	Active shedding is generally absent, although reactivation can occur
Progressive infection	The virus continues to replicate and reaches tissues such as bone marrow	Antigen tends to remain detectable, and PCR can help classify the infection	The cat sheds virus and can infect other cats

Cornell University describes these three responses and notes that kittens are at greater risk of progressive infection. The table explains the process. It cannot classify a cat at home because timing of exposure and the combination of tests affect interpretation.

How does FeLV spread between cats?

Transmission requires contact with a cat that is shedding the virus. Saliva plays a major role, so mutual grooming, bites and close, prolonged contact matter. The virus may also be present in nasal secretions, milk, urine and feces, and an infected mother can pass it to her kittens.

FeLV survives for only a short time outside the body. A brief encounter, or simply being in a place where another cat has been, does not carry the same risk as living, eating and interacting every day with a cat that has progressive infection. Cornell explains that environmental transmission without prolonged close contact is unlikely.

Before introducing a new cat to resident cats, keep them separate and arrange a veterinary visit. Outdoor access, origin, age, contact with cats of unknown status and the date of possible exposure help the veterinarian decide when to test and whether a repeat test is needed.

In a home with one positive and one negative cat, physical separation is the safest way to prevent transmission. Vaccinating the negative cat can reduce risk but does not provide complete protection. Decisions about shared living need to consider confirmatory results, whether separate spaces are practical and the animals’ welfare.

Why does a positive result need interpretation?

The rapid clinic test usually looks for the viral p27 antigen in blood. It is a useful screening tool, but a positive result should not become an instant verdict. The Feline Veterinary Medical Association recommends testing newly acquired, ill or exposed cats and interpreting results as part of a plan.

Depending on the situation, the veterinarian may confirm the finding with another antigen test, PCR or immunofluorescence. They may also repeat the sample after an interval based on the possible exposure date. Cornell warns that one test at one time point cannot determine progressive infection.

A negative result soon after a recent exposure may also need repeating because antigen does not appear immediately. Discordant results may reflect early infection, regressive infection or limitations of the method. Until the status is clear, treat the cat as potentially infected and prevent contact with negative cats.

A bone marrow examination is not the routine next step for every positive rapid test. It may be used to investigate blood abnormalities, leukemia or another specific disease. The Merck Veterinary Manual explains that confirmation usually begins with laboratory antigen testing or PCR.

Which signs need veterinary attention?

Many infected cats have no signs at first. When signs occur, reduced appetite, weight loss, a poor coat, persistent fever, pale gums, enlarged lymph nodes, mouth inflammation, diarrhea or repeated infections may be involved. None of these signs confirms FeLV because other diseases can look similar.

Seek immediate care if your cat has trouble breathing, breathes with an open mouth, collapses, has a seizure, becomes profoundly weak, has bleeding that will not stop, or develops blue or very pale gums. Do not wait for an FeLV test before treating an emergency.

Refusal to eat, fever, vomiting, diarrhea, mouth sores, sudden behavior change or a worsening infection also warrant prompt contact with the veterinary team. Treatable problems can become more severe in a cat with FeLV, so seek an assessment early.

The Merck Veterinary Manual recommends fully investigating blood count abnormalities, even in a positive cat. Blaming every change on the virus can hide a treatable condition and delay the right care. To prepare a clear history without trying to diagnose the problem yourself, read what to note before the veterinary visit.

Where does vaccination fit into prevention?

FeLV vaccination lowers the chance of progressive infection, but no vaccine provides complete protection. A cat should be tested before the first dose. Vaccinating a cat who is already infected does not treat FeLV and does not change an antigen test result.

The AAHA and AAFP guidelines consider FeLV vaccination essential for kittens through one year of age and for cats at risk of exposure. After that stage, the decision and interval depend on age, the product used and lifestyle. Unsupervised outdoor access, living with positive cats or cats of unknown status, and frequent changes in group housing increase risk.

Vaccination does not replace testing new cats, controlling outdoor access or separating positive and negative cats. The European ABCD guideline states that no FeLV vaccine prevents every infection. Bring the vaccination record to the appointment so the team can build an individual plan. Do not bring doses forward or repeat them without veterinary advice.

How do you care for a cat with FeLV?

There is no definitive cure for the infection, but many associated problems can be treated. A positive cat who is clinically well should not receive medication simply to “boost immunity” without a specific indication. The team monitors weight, the mouth, skin, eyes and lymph nodes, and looks early for infection, anemia or other changes.

The Merck Veterinary Manual recommends preventive examinations at least every six months, with laboratory monitoring tailored to the patient. An unwell cat may need closer follow-up. Changes in appetite, weight, activity, urination, stool or breathing should not be saved until the next routine visit.

Keep the cat indoors, using secure screens or an enclosed outdoor space. This limits new exposure to infectious agents, fights and transmission to other cats. Feed a complete diet suited to the cat’s life stage and avoid raw diets, which increase exposure to microorganisms. Fresh water, clean litter boxes, parasite control, dental care and fewer conflicts between cats also support daily health.

Prognosis varies with the response to infection, other diseases and access to care. Some cats remain clinically well for years. A positive result alone is not a reason for euthanasia and does not prevent responsible adoption. The team should base the plan on that cat’s results, health and household.

Frequently asked questions

Can FeLV spread to people or dogs?

No. Feline leukemia virus is specific to felids and does not infect people or dogs.

Can a vaccinated cat still get FeLV?

Yes. The vaccine does not protect every cat from every exposure. It reduces risk and needs to be combined with testing and prevention of contact with cats that shed the virus.

Can the vaccine make a rapid test positive?

No. Common rapid tests detect viral antigen, and FeLV vaccination does not cause a positive result on this type of test.

Does one positive test confirm progressive FeLV?

Not always. The result needs to be interpreted alongside history, timing of exposure and, when indicated, confirmation or repeat testing. Do not make irreversible decisions based on screening alone.

Can cats with FeLV live together?

Confirmed positive cats can share a home when they are socially compatible and receive veterinary care. A negative cat is at risk when living with a cat that sheds the virus, so separation is the safest option.

Is there a cure for FeLV?

There is no definitive cure that eliminates the infection. The veterinarian treats associated diseases, limits new exposures and monitors the cat so changes can be addressed early.

Does every cat with FeLV develop cancer?

No. Infection increases the risk of lymphoma and other diseases, but outcomes differ. Regular visits help investigate signs without attributing every change to the virus.

Plan the next step

If there has been a positive result, recent exposure or a new arrival, write down the dates, separate the cats and arrange an assessment. The free guide available below expands on care and is written in Brazilian Portuguese. You can also explore the Criando Elos courses for more on signs and prevention.