Feline leukemia virus (FeLV) is a contagious viral infection that affects cats worldwide. Known for weakening the immune system, FeLV makes cats more vulnerable to other infections, anaemia, and certain cancers. Spread primarily through close contact, such as grooming or sharing food bowls, the virus is particularly dangerous to kittens and cats with weakened immune systems. While not every infected cat will show symptoms immediately, the long-term impact of FeLV can be severe, and there is currently no cure. However, vaccinations are available to protect against it, and early detection through routine testing can improve a cat’s quality of life. Understanding the risks and taking preventive measures is key to keeping your cat safe from the feline leukemia virus. This article will explore the virus’s effects, how it spreads, and the best ways to manage FeLV in both domestic and feral cat populations.
Feline leukemia virus is one of the most common—and most dangerous—infectious diseases that can affect our feline friends. According to data from Cornell University, as many as three percent of the kitties in the U.S. and Canada are affected. That’s the point of Feline Leukemia Day, which falls on July 15th every year and is dedicated to raising awareness about this dangerous disease. Read on as a local vet discusses leukemia in cats.
What Is Feline Leukemia?
FeLV is a retrovirus that can cause other serious health problems, including cancer, skin infections, eye problems, respiratory issues, and blood disorders. It also weakens Fluffy’s immune system, which will make her more vulnerable to other health issues, such as lymphoma.
How Long Do Cats Live With FeLV?
The exact time frame is going to vary from kitty to kitty. Fluffy’s age and health are both factors. Her viral load may also change over time. The effects on a cat’s immune system also come into play here, as FeLV-positive felines are at risk of secondary infections.
Most adult cats diagnosed with feline leukemia virus can live between two to six years. However, infected kittens tend to have a shorter lifespan, typically ranging from six months to two years.
Can Feline Leukemia Be Cured?
Unfortunately, there is no cure. However, many kitties go on to live long happy lives, even after diagnosis.
How Do Cats Get Feline leukemia?
Unlike the types of leukemia that infect humans, feline leukemia is contagious. It’s usually spread through close contact, such as when kitties snuggle or groom each other. It can also be spread through bites, fighting, and even shared bowls. Mothers can also pass it on to their kittens.
It’s worth noting that the virus is usually transmitted through saliva, rather than urine or feces.
Some cats are at higher risk than others for feline leukemia virus. The biggest risk factor is remaining unvaccinated. Cats that live outdoors or are allowed outside face increased exposure. Fluffy could also contract feline leukemia virus if she spends time with an infected cat. This is why we always recommend keeping newly adopted pets separate from current pets until your vet confirms they’re healthy.
On a brighter note, the virus cannot live long outside a host’s body.
Can People Catch Feline Leukemia?
No. Those of you with dogs can breathe a sigh of relief: our canine friends are not at risk, either. Nor are any other animals. However, it is extremely contagious to other cats, which is why we always recommend keeping infected kitties inside. (Note: we actually recommend keeping all cats inside, just as a matter of proper pet care. Kitties are much safer indoors, where they aren’t at risk from weather, cars, traffic, or other hazards. If you’re worried about your cat getting bored indoors, check out our article on 6 Ways to Keep Fluffy Out of the Tree for some indoor enrichment ideas.)
How Is FeLV Treated?
There is no standard treatment for feline leukemia virus (FeLV) itself. However, infected cats are often at risk of developing secondary infections, for which treatments may be available. For example, your vet may recommend antibiotics, anti-inflammatories, or appetite stimulants. In some cases, cats may benefit from blood transfusions.
That said, it’s important to keep in mind that every cat is different. The exact recommendations will always be offered on a case-by-case basis, after the kitty has been diagnosed and evaluated.
What Are The Stages Of Feline Leukemia?
FeLV has three separate stages. This isn’t necessarily a linear progression from one to the next.
The stages are as follow:
Abortive Infection and Immunity
At this point, the virus is beginning to replicate. Most cats do not show any symptoms in the first stage. In fact, kitties with healthy immune systems may beat the virus at this point. About one in three felines never progress past this stage.
Progressive Infection and Disease
At this point, the virus is spreading, and will reach Fluffy’s lymph nodes and gastrointestinal system. Your pet will begin shedding virus, and will be contagious to other cats. As the disease progresses, it will eventually get into your pet’s marrow. At that point, there is no longer a chance of her beating the virus.
Regressive Infection and Immunity
This is similar to remission. Kitties that have beaten off the virus are in the regressive phase. This is sometimes temporary. However, some cats with regressive FELV may never develop any issues related to FeLV. They also are not typically contagious.
Ask your vet for more information.
What Are The Signs Of FeLV?
Most of the time, the first thing you will see is diarrhea and vomiting. This isn’t going to be the once-in-a-while-tummy-upset or hairball incident: it will become quite persistent and tends to get worse over time. Fluffy may also have trouble keeping her food down.
Fever
Fever is also not uncommon in kitties that have feline leukemia. It may be a mild fever at first, but that isn’t always the case. Fluffy may also get quite sick.
Pale Gums
Another thing you may notice on your feline pal is pale gums. This often goes hand in hand with fever.
Weakness
Over time, the effects of feline leukemia virus will start to add up and take a significant toll. Fluffy may become weak and lethargic, showing little interest in play and spending most of her time lying in bed. While it’s normal for cats to lounge, healthy ones still respond to stimuli, like the sound of a can opener, and will perk up for meals, cuddles, and playtime. In contrast, a cat affected by the feline leukemia virus may not show these typical signs of engagement.
Lack Of Interest In Food/Water
Any time a cat loses interest in food, it’s a cause for concern. This is a symptom of many different illnesses in cats.
Fluffy may also lose interest in drinking water, which can quickly lead to dehydration.
Respiratory Issues
It’s also not uncommon for cats to develop respiratory issues, particularly in the later stages of the disease. You may notice your pet wheezing, rasping, or just having trouble breathing.
Seizures
Fluffy may also get seizures. In some cases, cats will display behavioral changes. Some develop neurological disorders.
Keep in mind that many of these symptoms are also signs of several other health issues. If you notice any of them in your feline pal, contact your vet right away.
Should I Adopt a FeLV-Positive Kitty?
Sadly, many cats that are FeLV positive have a very hard time finding loving homes. That’s very sad, since, as mentioned above, kitties with feline leukemia may have many great years ahead of them. You will need to be aware that Fluffy may need to see her doctor a bit more than other kitties. Aside from that, you’ll just need to keep her happy and comfortable indoors. Ask your vet for tips.
What If My Cat Is Diagnosed With FeLV?
The important thing to remember is that a FeLV diagnosis is not a death sentence. Fluffy may have several years of purrs and pounces ahead of her!
If your feline pal has been diagnosed, you’ll want to get specific information and advice from your vet. Because every pet is different, it’s important to get custom advice.
How Do I Protect My Cat From FeLV?
Fortunately, we have a very simple solution: just get your furry pal vaccinated! If your kitty hasn’t been vaccinated, or if you have questions about her immunization, reach out to your vet right away. Spaying and neutering also helps, as it reduces the risk of Fluffy fighting or getting into close contact with other cats.
Conclusion: Feline Leukemia is fairly common in cats, affecting between 2 and 3 percent of kitties in the U.S. and Canada. It can weaken your pet’s immune system, and will render her susceptible to other health conditions, such as skin infections, urinary tract infections, and cancer.
Understanding Feline Leukemia Virus in 2025: Immunity and Vaccination
How has the prevalence of FeLV changed over the past 25 years?
The prevalence of Feline Leukemia Virus (FeLV) has decreased significantly over the past 25 years, primarily due to increased awareness, vaccination efforts, and improved testing methods. Once a major concern in feline populations, FeLV now affects about 2-3% of cats in the U.S. and Canada. This reduction is a result of pet owners vaccinating their cats and keeping them indoors, reducing the spread of the virus. Additionally, spaying and neutering programs have helped limit cat-to-cat contact, further minimizing transmission of the virus.
How long can the virus survive outside a cat’s body?
Feline leukemia virus (FeLV) does not survive for long once outside a cat’s body. It is highly contagious among cats but loses viability quickly when exposed to the environment. Typically, the virus can only remain active for a few hours in typical household conditions, making direct cat-to-cat contact the primary transmission method. This short survival time outside the host underscores the importance of maintaining good hygiene and prompt disposal of waste to prevent FeLV spread among cats.
What are the different stages of FeLV infection?
Feline leukemia virus (FeLV) progresses through three distinct stages. Initially, during the Abortive Infection and Immunity stage, the virus begins replication but often does not produce symptoms, and some cats with strong immune systems may eliminate the virus. If the infection progresses, it enters the Progressive Infection and Disease stage, where the virus spreads to lymph nodes and gastrointestinal systems, making the cat contagious and eventually affecting the bone marrow. The final stage, Regressive Infection and Immunity, resembles remission; some cats may not show further symptoms and typically are not contagious.
What percentage of cats can eliminate the virus on their own?
About 33% of cats exposed to the Feline Leukemia Virus (FeLV) may naturally eliminate the virus during the initial abortive infection stage. These cats show no symptoms and effectively clear the virus, preventing its progression to more severe stages of the disease. This capacity to fight off FeLV is primarily attributed to a robust immune response, allowing these individuals to maintain a virus-free state without further health complications related to FeLV.
At what age should kittens start receiving FeLV vaccines?
Kittens should begin receiving vaccines for Feline Leukemia Virus (FeLV) as early as eight weeks old. This early vaccination is crucial because young cats are especially susceptible to FeLV, which can lead to severe health issues including immunodeficiency and cancer. The initial vaccine is followed by a booster shot a few weeks later to ensure adequate protection. Regular veterinary consultations are advised to determine the best vaccination schedule based on the kitten’s health, environment, and lifestyle. Vaccinating early helps protect against this contagious and potentially life-threatening virus.
Book An Appointment At Our Pet Clinic
Do you need to bring your feline buddy in for an exam or vaccinations? Our clinic offers comprehensive veterinary diagnostics services to ensure early detection and proper management of conditions like FeLV. Please feel free to contact us, your animal clinic, anytime.