Feline Leukemia Virus (FeLV): A Comprehensive Guide To Transmission, Symptoms, Diagnosis, And Prevention

Feline Leukemia Virus (FeLV) is a retrovirus that infects cats. It is one of the most common and serious infectious diseases in cats worldwide, acting as a major cause of illness and mortality by suppressing the immune system and leading to cancer, blood disorders, and secondary infections.

1. Transmission: How Cats Become Infected

FeLV is primarily spread through close, social contact. The virus is fragile and cannot survive long in the environment (only minutes to hours), so transmission requires prolonged, intimate contact. The virus is shed in:

• Saliva
• Nasal secretions
• Blood
• Milk
• Urine and Feces

Common transmission routes include:

• Mutual grooming
• Sharing food and water bowls
• Sharing litter boxes
• Bite wounds
• From an infected queen to her kittens

2. Infection Outcomes: Not All Infections Are The Same

After exposure, a cat's immune response determines the outcome:

• Abortive Infection (Rare): The cat mounts a strong immune response, eliminates the virus completely, and becomes immune.
• Regressive Infection: The virus enters the body and may initially replicate, but the cat's immune system eventually contains it. The viral DNA remains in the cat's body (often in the bone marrow), but the virus is not actively replicating. These cats:

Are not contagious to other cats.

Typically live healthy lives.

May rarely reactivate the virus if severely immunocompromised.

May test negative on routine screening tests but positive on more sensitive PCR tests.

• Progressive Infection: The cat's immune system fails to fight off the virus. The virus replicates persistently in the blood and bone marrow. These cats:

Are contagious and shed large amounts of virus.

Will almost certainly develop FeLV-related diseases in their lifetime.

Have a significantly shortened lifespan; >80% die within 2-3 years of diagnosis from complications.

3. Clinical Signs: Symptoms Of The Disease

FeLV does not have one specific set of symptoms. It weakens the immune system, leading to a wide variety of secondary diseases. Signs are often vague in the early stages ("latent" phase) and can include:

• Lethargy, weakness
• Loss of appetite
• Weight loss
• Poor coat condition
• Persistent or recurrent fever
• Persistent or recurrent infections (e.g., respiratory infections, skin infections, bladder infections)
• Gingivitis (inflamed gums) and stomatitis (oral inflammation)
• Swollen lymph nodes
• Various eye conditions
• Neurological disorders (e.g., seizures, behavior changes)

As the disease progresses, it can cause:

• Anemia: Due to bone marrow suppression (pale gums, weakness).
• Cancer: Particularly lymphoma (cancer of the lymphatic system) and leukemia (cancer of the blood cells).
• Reproductive problems: Infertility, abortion of kittens.

4. Diagnosis: How It's Detected

Diagnosis is made through blood tests performed by a veterinarian.

• ELISA (Enzyme-Linked Immunosorbent Assay): This is the common in-clinic screening test. It detects a viral protein (p27 antigen) in the blood. It can identify cats in the early (viremic) phase of infection.
• IFA (Immunofluorescence Assay) or PCR (Polymerase Chain Reaction): These are confirmatory tests usually sent to a reference lab.

IFA detects viral antigen inside white blood cells, indicating a more advanced, established infection.

PCR detects viral DNA.

J&G's Feline Leukemia Virus Antigen Test Kit is recommended.

Advantages：

• High Accuracy and Reliability
• Fast Results: Result in 5-10 minutes
• Simple Procedure, No specialized equipment or instrumentation is needed.
• Room Temperature Storage: 2-30℃
• High Cost-Effectiveness
• Multiple Sample Types: Serum, plasma or whole blood
• Clear and Easy-to-Read Results

5. Management And Treatment: There Is No Cure

There is no cure for FeLV. Management focuses on providing a high quality of life, treating secondary conditions, and preventing spread.

• Keep the cat indoors strictly to prevent:

Exposure to other pathogens their weakened immune system can't fight.

Spreading the virus to other cats.

• Provide excellent nutrition with a high-quality, palatable diet.
• Schedule regular veterinary check-ups (at least every 6 months) to monitor weight, dental health, and overall condition, including blood work.
• Treat secondary infections and complications promptly with antibiotics, anti-inflammatories, or other medications.
• Treat specific conditions like anemia (with steroids, blood transfusions) or cancer (with chemotherapy).

6. Prevention: The Best Strategy

Prevention is far more effective than treatment.

• Vaccination: FeLV vaccines are available and are considered a "core" vaccine for kittens and a "non-core" vaccine for adult indoor-only cats. Discuss your cat's risk factors with your veterinarian. Vaccination is not 100% effective, but it significantly reduces the risk of infection.
• Test and Isolate: All new cats or kittens entering a multi-cat household should be tested for FeLV before introduction. Any positive cat should be isolated from FeLV-negative cats.
• Keep Cats Indoors: This is the single most effective way to prevent exposure to the virus.
• Prevent Fighting: For cats that go outdoors, ensure they are vaccinated and try to minimize opportunities for fights with stray cats.

Summary: FeLV is a serious, often fatal disease. Responsible ownership through testing new cats, keeping cats indoors, and vaccinating at-risk individuals is the key to controlling this virus. If your cat is diagnosed, work closely with your veterinarian to provide the supportive care they need to live a comfortable life.