What is Feline Leukemia? Diagnostics, Prevention, and Treatment Measures

“Have you ever tested for feline leukemia?” “Have the other cats at home been tested for Feline Immunodeficiency Virus?” “If your cat goes outdoors, regular checks for FIV are essential!”

These phrases are probably the most frequently spoken during feline clinic visits. You might wonder: Aren’t feline leukemia and AIDS only transmitted through fights with stray cats? But my cat never goes outside, so is this really important to me? Of course, it is!

The horror of leukemia lies in the fact that:

A cat may appear healthy but could still have leukemia, and a previous negative screening does not guarantee perpetual negativity!

What Happens If You Get Leukemia?

As the name suggests, the most severe form of the leukemia virus is inducing feline leukemia, where abnormal bone marrow continuously produces dysfunctional white blood cells. This not only affects the immune function of the body but may also impact various stem cells within the bone marrow, leading to severe anemia and thrombocytopenia; the leukemia virus may also induce the occurrence of lymphoma, growing substantial masses in the body and causing serious symptoms in the affected areas. Any single one of these situations is enough to cost a cat its life, and they may all occur simultaneously.

Leukemia is a disease that “strikes silently but fiercely,” with the virus potentially lying dormant for several years without any symptoms in the cat. However, when the virus reactivates, symptoms usually come on quickly and severely, catching the family off guard.

How to Contract Feline Leukemia?

Feline leukemia is a viral disease, similar to the human immunodeficiency virus, belonging to the Retroviridae family. Infected animals shed the virus in bodily fluids (saliva, nasal secretions, milk, urine, feces, etc.), thus there are two main routes of transmission:

1. Vertical transmission: Infected queens transmit the virus to their kittens through milk.
2. Horizontal transmission: Cats in close contact or fighting transmit the virus through bodily fluids (saliva, nasal secretions, feces, urine). Most infections occur when the virus enters the body through the mouth or nose, but it can also enter through fight wounds.

Kittens are at the highest risk of infection!

Another retrovirus that infects cats is the Feline Immunodeficiency Virus (FIV).

What Happens After Exposure to the Virus?

Depending on the immune status of the infected cat and the amount of virus they are exposed to, there are three different outcomes:

1. Abortive infection: The cat’s immune system completely eliminates the virus before it reaches the bone marrow, with no leukemia-related symptoms in the future.
2. Regressive infection: The virus successfully enters the bone marrow, and its genes are integrated into the cat’s own DNA. However, the immune system can still confine the virus within the bone marrow, preventing it from replicating extensively outside the marrow. This stage is quite troublesome for pet owners and veterinarians because leukemia cannot be detected by general rapid screening at this time. Cats in this stage do not shed the virus, but if their immune function declines, it may evolve into a progressive infection.
3. Progressive infection: The virus successfully enters the bone marrow, and the immune system is too weak to cope, allowing the virus to use the cat’s resources to replicate extensively throughout the body, causing a range of symptoms. Cats entering this stage will usually die within a few years due to leukemia-related diseases.

Diagnosis of Feline Leukemia

Since leukemia conditions within the body are highly variable and can affect the health of current and future cats living together, early detection of leukemia is crucial. The American Association of Feline Practitioners (AAFP) recommends screening for feline leukemia at the following times:

1. When you first acquire the cat.
2. Before administering the leukemia vaccine.
3. After potential exposure to an infected cat, such as after straying.
4. When exhibiting symptoms such as fever, lymph node enlargement, blood abnormalities, etc.

Leukemia can be diagnosed if the leukemia virus is detected in the cat’s body. Various diagnostic methods have been developed for different viral structures, each with its advantages and suitable times for use.

1. Detecting the p27 protein on the surface of the virus: Common in-house rapid screening tests check for the p27 protein.
2. Detecting viral RNA: RT-PCR.
3. Detecting the DNA after viral RNA is reverse transcribed: PCR

https://veteriankey.com/feline-leukemia-virus-infection

Since rapid screening has a short test time and is easy to perform, it is one of the most suitable tools for diagnosing leukemia:

• If the rapid screening result is positive, it indicates the presence of p27 protein in the blood, evidence that the leukemia virus is replicating extensively.
  • It may represent the early stages of regressive infection, progressive infection.
  • It is contagious at this time.
  • Since it can significantly impact the cat’s health, if it is a cat with a low risk of infection, it is best to combine it with other tests for a comprehensive assessment, especially for low-risk cats (such as healthy cats, strictly indoor cats).
  • False-positive results are most likely due to improper handling of the sample.
• If the rapid screening result is negative, it indicates the absence of p27 protein in the blood, no extensive replication of leukemia virus, but it does not mean ‘completely none’ of the leukemia virus. If the cat continues to be at risk of exposure or shows possible symptoms, it is still necessary to screen again.
  • It may represent no exposure to the leukemia virus, failed infection, regressive infection.
  • Since the p27 protein needs to be produced, it may take 30 days to be detected, so if rapid screening is done within 30 days after adoption or exposure risk, there may be a false-negative result.
• If there is doubt about the rapid screening results, it is necessary to discuss with a veterinarian to conduct other examinations to more accurately determine the infection status of leukemia.

Rapid screening positive: Likely infected and likely to spread to other cats.

Rapid screening negative: High chance of not being infected, but be cautious of the 30-day window period after recent exposure.

How to Prevent Feline Leukemia?

Let’s review how the leukemia virus spreads, including close contact through saliva transmission (grooming, nursing, sharing food/water/litter boxes, fighting), or through other bodily fluids (blood transfusion, placenta). Avoiding these risks is the first step in prevention.

Leukemia Vaccine

The vaccine can protect cats from progressive infection and the development of related diseases, but it cannot ensure that the virus’s genes embedded in the cat’s bone marrow cells after exposure (regressive infection), so it cannot be said that the vaccine can completely prevent infection with the leukemia virus. However, the symptoms we fear most from the leukemia virus (immune anemia, lymphoma, etc.) may be avoidable through vaccination.

That being said, the leukemia vaccine is often discussed alongside the notorious ‘vaccine-associated sarcoma’ or ‘injection-site sarcoma.’ These sarcomas are highly aggressive malignant tumors, believed to be related to local tissue reactions caused by injections, with leukemia vaccines often being the prime suspects due to their adjuvants that stimulate immune responses.

Many cat owners may have the contradiction of ‘not vaccinating for fear of infection, but vaccinating for fear of tumors,’ so we need to assess the ‘risk of exposure’ at the same time. If a cat never goes outdoors and has no chance of contact with other cats, the risk of infection may be lower than the risk of tumors; on the contrary, if the cat is kept outdoors or is naturally aggressive, the risk of infection will be far higher than the risk of tumors.

In addition, the vaccine does not have a therapeutic effect on cats that have already been infected with the leukemia virus, so it is necessary to confirm the infection status with rapid screening before vaccination.

The risk of leukemia development is far higher than the risk of tumors caused by vaccination, so cats that may be exposed to the leukemia virus must be vaccinated.

Home Prevention Measures

Avoiding contact with cats that may be infected with leukemia is the best prevention method, so avoid letting cats roam outdoors freely and avoid sharing food utensils with unknown cats. The leukemia virus is very unstable outside the host, and common disinfectants or alcohol can kill the virus, preventing indirect transmission between cats.

If there is already an infected cat at home, efforts should be made to prevent other cats from getting infected:

• Prevent the infected cat from roaming outdoors freely.
• Infected cats should be isolated from other cats in the home and should not share food or litter boxes.
• If there are newly raised cats at home, they should also be isolated before confirming their leukemia status.
• Other uninfected cats in the home should be vaccinated for leukemia, and contact should still be avoided for three weeks after the second dose.
• Infected queens should be spayed to avoid reproduction.

What to Do If a Cat Has Leukemia?

Cats infected with the leukemia virus may not show any symptoms. However, when the cat is in a stressful environment (such as drastic environmental changes), the virus may awaken from dormancy or begin to replicate extensively, leading to subsequent symptoms. When there are no symptoms, we must regularly monitor the cat’s condition so that we can detect and handle issues early.

Preventive Measures

• Basic health check-ups: every six months;
• Complete blood count: every six months;
• Serum biochemistry tests, urine tests: annually;
• Weight: every 2-4 weeks. Changes in weight may occur earlier than any other symptom;
• Regular prevention of internal and external parasites and heartworms;
• Regular administration of core vaccines;
• Maintain a balanced diet, prohibit raw food;
• Recommend sterilization.

Therapeutic Measures

When cats with the disease show symptoms related to leukemia, medical intervention is required. Veterinarians need to distinguish whether these symptoms are caused directly by the leukemia virus or are secondary after the leukemia has compromised immune function; the treatment direction may vary greatly.

If it is a secondary disease, it may be more difficult to manage than cats without leukemia, requiring more frequent monitoring. Inflammatory oral diseases may require full-mouth tooth extraction for long-term control.

For the leukemia virus itself, there are currently antiviral drugs and interferons available, but more extensive research is needed to verify their effectiveness.

Summary

The feline leukemia virus is very cunning, it may cause disease as soon as it infects, with symptoms that vary greatly; it may also hide in the bone marrow for a long time, waiting for the right conditions to cause a big outbreak. Therefore, rapid screening at the right time can not only detect and treat the disease early but also prevent the spread of the disease. Regular vaccination is necessary when there is a risk of exposure to the virus.