All You Need to Know About Feline Leukemia

Understanding Feline Leukemia Virus (FeLV)

Feline Leukemia Virus (FeLV) is a significant infectious disease that affects cats worldwide. It is a cat specific virus retrovirus, which means FeLV has the ability to incorporate its genetic material into an infected cat's DNA but does not affect other species. This integration allows the virus to persist over time and can lead to chronic health issues. Cats that are persistently infected with FeLV can shed the virus in their saliva, feces, urine, and milk, posing a risk of transmission to other felines. It is especially important to monitor and manage FeLV risks in environments where cats have close contact, such as multi-cat households or when cats venture outdoors.

How Prevalent is Feline Leukemia?

Feline Leukemia Virus remains an important health concern for cats, with an impact on 2-3% of the feline population in the United States. In cats that are already ill or at higher risk, the infection rates are significantly greater, reaching up to 30% in some cases. It is encouraging to note that over the past quarter of a century, there has been a considerable reduction in the prevalence of FeLV. This decrease is largely attributed to widespread spay and neuter programs, vaccination efforts, availability of tabletop screening tests, and additional testing methods.

Importance of Knowledge on Feline Leukemia

Understanding Feline Leukemia Virus is not only important for the health of your cat but also for the well-being of other cats in your community. Knowledge of this disease can aid in preventing its spread, ultimately improving the quality of life for affected felines. Furthermore, being informed about FeLV can help pet parents make crucial decisions about their cats' health and lifestyle, such as the necessity of vaccinations or the risks associated with outdoor access. Being well-informed also aids in managing any potential risks to other felines they may come into contact with, whether at home or outdoors.

Brief on Feline Leukemia Symptoms

In the early stages of an infection with the Feline Leukemia Virus, cats often show no signs of illness. As the virus affects the cat's system, observable but vague symptoms might emerge, including a loss of appetite, weight loss, and poor coat condition. The virus may progress to more serious health complications, such as secondary infections, anemia, and sadly cancer. Recognizing these symptoms early can be pivotal for prompt and effective management of the illness, which can significantly improve quality of life.

Transmission and Risk Factors of Feline Leukemia

How Feline Leukemia Spreads

Feline Leukemia Virus is contagious and has several potential methods of transmission. Close contact is generally needed for spreading this virus as it is not very hearty in the environment outside of the cat. The main forms of transmission include:

Mother to Kitten Transmission

Infected mother cats may pass the virus to their kittens either in utero or through nursing. Preventing unintended breeding is important for curbing this vertical transmission and controlling the spread of FeLV.

Bite Wounds

FeLV can be transmitted through saliva, especially when the saliva is introduced into the bloodstream such as with a deep bite wound.

Mutual Grooming

Cats that groom each other can share saliva transferring the virus. This is more likely in long term situations such as cats living within the same household.

Shared Food or Water Dishes and Litter Boxes

While less common, the sharing of feeding stations and litter boxes can be a potential source of shared bodily fluids and infection.

By recognizing these risk factors, proactive measures can be taken to mitigate the spread of FeLV.

Identifying High-Risk Cats

Certain cats are at a higher risk of contracting Feline Leukemia Virus. Understandably, cats with weakened immune systems are at increased risk for contracting FeLV. Similarly, kittens are particularly vulnerable, given their still-developing immune systems. Kittens born to an infected mother will have an even higher risk of infection, potentially contracting FeLV while in the womb or through nursing. Other high risk populations include multi-cat households or shelters where infection status may be undetected and stress may be high. Finally, cats with access to the outdoors where they may interact closely with unknown cats are at increased risk. Understanding which groups of cats are at high risk can inform pet parents in their decisions regarding care and the lifestyles they provide for their pets.

Role of Age and Health in Feline Leukemia

The age and health status of a cat can significantly influence its susceptibility to Feline Leukemia Virus. Kittens and young cats are particularly vulnerable to FeLV due to their developing immune systems, which may not be fully equipped to ward off the virus. These youngsters often have not yet received the full course of vaccinations that can help protect against FeLV.

Cats that are already living with compromised immune systems or existing health conditions face a greater threat from FeLV. Conversely, healthy adult cats with a robust immune system and no underlying health issues have a lower risk of contracting the virus. Their bodies are typically better prepared to defend against FeLV, especially if they have been properly vaccinated.

For pet parents concerned about their cat's risk of FeLV, supporting their general health and getting timely vaccinations are key preventive measures.

Symptoms and Diagnosis of Feline Leukemia

Common Symptoms of Feline Leukemia

Cats suffering from Feline Leukemia Virus infections may show signs that intensify over time. Early in the infection process, cats will not show any outward signs of illness. Depending on how the cat’s immune system reacts to the virus, the cat will exhibit one of the three types of infection: abortive, regressive, or progressive.

• Abortive: Cats who are exposed to FeLV and clear the infection before it can insert its DNA into their genetic code have had an abortive infection. After the initial infection, these cats will not shed the virus and will not test positive for FeLV. However, they will have antibodies to the virus.
• Regressive: Approximately 30-40% of infected cats will suffer from a regressive infection in which the virus infects the cat’s bone marrow and/or organs before the immune system clears the infection from the bloodstream. The virus is not actively replicating nor circulating in the cat’s bloodstream so these cats appear healthy and do not shed virus. However, a regressive infection may become progressive.
• Progressive: Another 30-40% of cats suffer from a progressive FeLV infection and are unable to control the replication of the virus. As the virus spreads, these cats are contagious and will show more extreme signs of illness as well as being more susceptible to coinfections.

Common signs of infection range from a decrease in appetite to progressive weight loss, lethargy, persistent fever, swollen lymph nodes, and poor coat quality. As the infection progresses cats may suffer from FeLV associated diseases such as anemia, secondary infections, chronic inflammatory conditions of the intestines, mouth, nerves, or eyes, and cancers such as leukemia, lymphoma and lymphosarcoma. Given that many of these symptoms are not exclusive to FeLV and can overlap with other conditions, a veterinary consultation is crucial for an accurate diagnosis. Frustratingly, FeLV infected cats may suffer from flare-ups as their immune system’s strength waxes and wanes in response to stressors on their body or in their environment.

How Veterinarians Diagnose Feline Leukemia

Before going into detail it is important to note that a cat should never be euthanized based on the results of a single FeLV test. Even if FeLV is confirmed a healthy cat may have happy years ahead. Diagnosing Feline Leukemia Virus typically involves multiple tests to fully understand the stage of the infection and risk of transmission.

Initially, veterinarians use screening blood tests that can identify a specific protein from the virus, FeLV P27. Seeing this protein in the sample indicates the presence of the virus in the cat’s bloodstream. These screening tests are often able to be run quickly, in-clinic, with a small blood sample.

If a positive test result is found, further testing is important to determine whether the infection is progressive, regressive or abortive. A veterinarian may wish to repeat table top testing several weeks later, submit samples to test for the amount of FeLV P27 in the blood (a quantitative assay) or submit samples for the presence of the viral genetic material (a PCR test).

The timing and type of test recommended will depend on the cat’s physical exam findings, age, and history, particularly if there was recently a potential exposure to FeLV.

Understanding False Positives and Negatives

When testing for Feline Leukemia Virus, it's important to understand that tests can occasionally return false positives or false negatives. Like any tool, these tests offer helpful information when their limitations are understood and they are interpreted correctly. Additionally, any test result can be false when not performed correctly, when samples are not handled properly, or if the test itself is faulty, these scenarios are very rare but possible.

With FeLV, a false positive occurs when the test indicates the presence of the virus but a true retro-viral infection is not present. This is typically seen with transient infections, where a very recent exposure to the virus will be handled by the immune system and the virus cleared.

Conversely, a false negative suggests the cat is without infection when the virus is indeed present. This may occur in regressive infections where the viral load present in the blood periodically dips below the level of detection. Situations like this highlight why interpretation by a veterinarian is crucial. Your cat’s veterinarian will pair test results with physical exam findings, patient history, and any other available patient information when pursuing a diagnosis.

Treatment and Management of Feline Leukemia

Treatments for Feline Leukemia

Feline Leukemia Virus remains a challenging condition to treat, as there is no cure. Instead, the focus should be supporting overall health and managing complications or secondary conditions that arise due to the weakened immune system. Attempts to treat FeLV more directly are an area of ongoing investigation and focus on decreasing viral load as well as immune modulation. However, availability and potential side effects may make these tools impractical.

Managing a Cat with Feline Leukemia

Managing a cat with Feline Leukemia Virus requires vigilant oversight of their health and proactive steps to promote a stress-free environment, which can bolster their compromised immune system. It is imperative for cats with FeLV to have regular, usually biannual, veterinary visits; these check-ups are crucial for monitoring the progression of the disease, identifying potential comorbidities, and making necessary adjustments to their care. Additionally, veterinary attention should be sought early for any changes in behavior or new or worsening symptoms. Even healthy pets benefit from routine vet visits, as outlined in our post on 5 Reasons To Take Your Healthy Pet To The Vet, where we discuss the importance of preventative care in maintaining overall animal health and welfare.

Prevention of Feline Leukemia

Vaccination Against Feline Leukemia

Vaccination is a key strategy in preventing Feline Leukemia Virus. It is recommended as part of the core vaccines for kittens and young adult cats, those less than one year old. It is also considered a core vaccine for adult cats with a potential exposure to cats with positive or unknown FeLV status, such as those with outdoor access or living in multi-cat households. Testing for FeLV is recommended before beginning a vaccine series as vaccination is not recommended for an infected cat. Once the initial vaccine series has been completed the schedule for boostering depends on lifestyle and.ongoing risks. Fortunately, FeLV vaccines will not cause false positive FeLV results on tests routinely used in the United States which look at the P27 antigen.

Reducing Exposure Risk

Testing any cat for Feline Leukemia Virus before adding them into your family is an important step in mitigating risk to the other cats in your home. It is possible to provide a loving home to both cats with and without FeLV but it is difficult to do without knowing each cat’s needs.

The best way to protect cats from FeLV is to prevent their exposure to infected cats. This includes not sharing food and water bowls or litter boxes between infected and non-infected cats. Another way to reduce exposure to infected cats is to spay and neuter. This can benefit individual cats by changing their behavior as well as decreasing the burden of FeLV on the population at large.

Living with a Feline Leukemia Positive Cat

Lifestyle Changes for FeLV Cats

Cats with Feline Leukemia Virus may benefit from lifestyle changes to support their overall health. This can include optimizing their diet, encouraging regular light exercise, and decreasing stressors such as major changes to the home or routine.

Possibly the biggest lifestyle change is keeping FeLV-infected cats indoors. Cats who previously lived exclusively outside or had regular access to the outdoors may struggle with this adjustment. However, this recommendation serves to help stop the spread of the virus and to shield infected immune compromised cats from contracting other communicable diseases.

Preventing Further Spread

Preventing further spread of Feline Leukemia Virus is a crucial aspect of managing this disease. For cats in a single cat home, removing outdoor access will effectively achieve this goal. Ideally, cats in a multiple cat home would be separated into cohorts of FeLV positive and FeLV negative groups to decrease any further spread. Fortunately, the virus is not very hearty and doesn’t survive outside the cat for longer than a few hours. Routine cleaning efforts with regular household solutions are likely to be sufficient in killing the virus which typically requires extended intimate contact to spread. This means cats can take turns accessing the common areas if those areas are properly cleaned in between “shifts”. While this significantly decreases the chance of spread, there is still a risk of transmission and it is recommended that uninfected cats remain up to date on FeLV vaccination schedule to further mitigate their risk. People should always wash their hands between petting and handling cohorts to decrease the possible spread of FeLV to the negative cats or the spread of opportunistic infections to the positive cats.

End-of-Life Care and Considerations

While cats with Feline Leukemia Virus can live happy lives, the sad truth is those lives are often shortened because this disease is incurable and affects the immune system. The median survival time after an FeLV diagnosis is 2.5 years for cats with a progressive infection and approximately 80-90% of cats will die within 3-4 years of diagnosis. The prognosis for each cat will depend on the particulars of their case, what comorbidities they have, and their quality of life. One tool that may help veterinarians determine the prognosis for a specific case is quantitative PCR testing which looks at the viral load or amount of virus the cat is carrying. This test can be performed serially to gain a bigger view of whether the viral load is growing or decreasing over time which can help identify a shift into progressive FeLV. Even within progressive FeLV, a cat may have happy memories yet to make. Which is why, decisions about end-of-life care should be carefully considered in conjunction with your family veterinarian who understands the intricacies of the condition.

When it becomes clear that your feline's quality of life is suffering due to FeLV, our network of end-of-life veterinarians offer compassionate in-home euthanasia services. This allows pets to pass away peacefully in the familiar and loving environment of their own home. We provide the necessary guidance and resources through this challenging process, assuring that respect and love are maintained for your cherished companion's final moments. Whenever you are ready to schedule a home visit, we are here for you and your cat.