고양이 백혈병(FeLV) 예방접종 증상과 원인, 진단·치료와 관리 포인트 총정리

Feline Leukemia Virus (FeLV): A Complete Guide to Vaccination, Symptoms, Causes, Diagnosis, Treatment, and Management

Lifestyle & Age CareDiseasesMeongsiljang Veterinary Advisory Board

Feline leukemia virus (FeLV) is a contagious virus that weakens the immune system and can lead to malignant diseases, making vaccination essential. Early symptoms are often subtle, making early detection difficult, but regular check-ups and vaccinations can help prevent the disease.

Feline Leukemia Virus (FeLV) is a Contagious Viral Infection

A veterinarian preparing to vaccinate a cat.

Feline leukemia virus (FeLV) is a contagious viral infection that attacks the immune system, leaving infected cats with significantly weakened immunity and making them highly susceptible to other pathogens. - Cause of Infection: The virus spreads primarily through the saliva, saliva, and feces of infected cats. The risk of transmission is particularly high during physical contact while playing or when sharing food. - Transmission Routes: Infection can occur through contact with environments contaminated by saliva, saliva, or feces. Vertical transmission from mother to kitten is also possible. - High-Risk Groups: Extra caution is advised for households with multiple cats and for cats that spend significant time outdoors. - Importance of Prevention: Early prevention is key to improving survival rates, making regular check-ups and vaccinations essential. Because early detection can be difficult, prevention is the most effective approach.

Infection is Primarily Caused by Direct Contact with Other Cats

Feline leukemia virus (FeLV) is primarily transmitted through bodily fluids such as saliva, saliva, feces, and milk. Common transmission routes include mutual grooming, sharing food and water bowls or litter boxes, and bites during fights. Vertical transmission from mother to kitten is also possible, occurring either in utero or through nursing. Because sustained close contact is required for transmission, cats that go outdoors frequently or live with multiple other cats are at higher risk. However, the FeLV virus does not survive long in dry environments outside a host and is easily inactivated by disinfectants, soap, heat, and drying, making indirect transmission via contaminated objects or people unlikely.

Two cats grooming each other while playing

Main Symptoms Include Fatigue, Weight Loss, Fever, and Oral Ulcers

In the early stages of feline leukemia virus (FeLV) infection, symptoms are often subtle and easy to overlook. However, as the disease progresses, cats may experience increasing fatigue, loss of appetite, and rapid weight loss. Other possible signs include fever, excessive tearing, oral ulcers, frequent cold-like symptoms, dermatitis, and anemia. Some cats suffer from recurrent infections due to long-term immune suppression, and in severe cases, malignant tumors may develop. By the time symptoms become apparent, the cat may already be in a chronic stage of infection.

Symptoms Requiring Immediate Veterinary Care

If your cat is lethargic all day, has no appetite, suffers from persistent high fever, or experiences repeated vomiting and diarrhea, immediate veterinary care is necessary. These symptoms may indicate a progressing FeLV infection and carry a high risk of complications. Early diagnosis and treatment are crucial for improving survival rates, especially if symptoms persist for more than two weeks.

Diagnosis is Confirmed Through Blood Testing

Feline leukemia virus (FeLV) is confirmed through blood testing for an accurate diagnosis. - ELISA test: This test detects viral proteins in the early stages of infection, allowing for a quick positive result. - IFA test: This test is performed additionally to determine chronic infection status and checks whether the virus has penetrated blood cells. - Need for retesting: Since initial infections can sometimes be transient, a follow-up test after 3–4 weeks is necessary to confirm the diagnosis. - Differentiation from other diseases: A comprehensive evaluation by a veterinarian is essential to distinguish FeLV from other conditions with similar symptoms. - Accurate diagnosis: To ensure accurate results, the cat’s overall condition and medical history should also be considered before testing.

A veterinarian preparing for a blood test

Treatment Focuses on Symptomatic Management, and a Cure is Difficult

Feline leukemia virus (FeLV) is a viral disease, and since there is currently no specific treatment to eliminate the virus, supportive care (symptomatic treatment) to alleviate symptoms is the cornerstone of management. - Supportive Care: Because there are no medications that can eradicate the virus itself, treatment focuses on addressing symptoms such as dehydration, anemia, and secondary infections. - Complication Management: Antibiotics are used for bacterial secondary infections, while nutritional supplementation helps improve overall condition, minimizing complications like anemia, infection, and tumors. - Prevention of Secondary Infections: Due to compromised immunity, it is best to keep the cat indoors to prevent exposure to other pathogens. - Regular Monitoring: Routine veterinary check-ups and ongoing monitoring of the cat’s condition are essential. - Daily Care: Reducing stress and maintaining a consistent daily routine help support overall health.

A veterinarian administering an injection to a cat

Home Care Centers on Preventing Spread and Maintaining Health

When caring for an infected cat at home, the most important step is to completely isolate it from other cats. - Bowls and litter boxes: Use separate items and disinfect them regularly to prevent contamination. - Handwashing and hygiene: Always wash your hands after contact, and clean the environment after handling the cat. - Regular check-ups: Continuously monitor the cat’s condition through veterinary visits and blood tests. - Nutritional care: Provide a balanced diet and offer a quiet environment to reduce stress. - Daily routine: Feed at consistent times and maintain a balanced mix of play and rest to support overall health.

A quiet space set up exclusively for infected cats

Breed-Specific Considerations and Prevention of Recurrence

There is no clear evidence that certain breeds are more susceptible to FeLV infection, and the risk of infection varies depending on age and environmental factors. In particular, kittens under six months of age may be more vulnerable to infection. Since infected cats can carry the virus for life, they must be completely isolated from other cats, and going outdoors or sharing living spaces should be strictly prohibited. Vaccination is ideally started before exposure to the virus, and it is important to develop a tailored plan at the appropriate time based on a veterinarian’s assessment.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

When should kittens start receiving vaccinations against feline leukemia virus (FeLV)?

The first vaccination can be administered after 8 weeks of age, with the exact timing determined by your veterinarian based on your cat’s health status and risk of exposure to external pathogens. Regular check-ups are essential to develop a tailored vaccination plan.

What are the possible side effects after vaccination?

Mild fever, fatigue, and temporary swelling at the injection site may occur. Severe reactions are rare, but if symptoms persist or worsen, consult your veterinarian immediately.

Can an infected cat be kept with other cats?

Absolutely not. Infected cats can spread the virus to other cats, so complete isolation is necessary.

Can my pet still get infected even after being vaccinated?

While no vaccine provides 100% protection, vaccination significantly reduces the risk of infection. Regular check-ups and preventive care must go hand in hand for optimal effectiveness.

Can feline leukemia be transmitted to humans?

No, feline leukemia virus (FeLV) is not transmissible to humans. However, because it spreads very quickly among cats, prevention is crucial.

Comparison of FeLV Vaccination Timing and Types

Item	Vaccination Timing	Vaccination Type	Main Characteristics	Additional Recommendation
8 weeks of age	First vaccination	FeLV vaccine	Begins inducing immune response	Second vaccination needed 2–3 weeks later
12 weeks	Second vaccination	FeLV vaccine	Strengthens immunity	Third vaccination recommended 3–4 weeks later
16 weeks or older	Third vaccination	FeLV vaccine	Complete immunity formation	Booster vaccination after 1 year
After adulthood	Booster vaccination	FeLV vaccine	Maintains ongoing immunity	Repeat on a 1-year cycle

The vaccination timing is determined by the veterinarian based on the cat's health status and environment. Early vaccination is recommended for cats that go outdoors frequently, and a plan tailored to the individual situation is necessary.

Recommended Products and Selection Criteria for Managing Dogs During Winter Cold Snaps and Preventing Hypothermia

Top Recommended Products for Canine Weight and Obesity Prevention and Management, and Key Selection Criteria

The Best Health Care Recommendations and Selection Criteria for Dog Travel and Transportation

Dog Nail Care: A Complete Guide to Symptoms, Causes, Diagnosis, Treatment, and Management

Comprehensive Guide to Dog Microchip Implantation: Symptoms, Causes, Diagnosis, Treatment, and Care

Puppy Indoor Safety Check: Symptoms, Causes, Diagnosis, Treatment, and Management Essentials

Complete Guide to Choosing and Comparing Heartworm Preventives for Dogs: Symptoms, Causes, Diagnosis, Treatment, and Management

Comprehensive Guide to Symptoms, Causes, Diagnosis, Treatment, and Management for a Puppy’s First Vet Visit

Comprehensive Guide to Preventing External Parasites in Dogs (Ticks and Fleas): Symptoms, Causes, Diagnosis, Treatment, and Key Care Tips

Early Detection of Health Issues in Dogs: Symptoms, Causes, Diagnosis, Treatment, and Management Essentials

References

[1] American Association of Feline Practitioners (AAFP). 2020 Feline Vaccination Guidelines. J Feline Med Surg. 2020;22(1):3-26.

[2] World Small Animal Veterinary Association (WSAVA). 2020 WSAVA Guidelines for the Prevention and Management of Feline Leukemia Virus Infection. Vet Rec. 2020;187(1):1-12.

[3] Hartmann K, et al. Feline Leukemia Virus Infection: A Review of Pathogenesis, Diagnosis, and Management. Vet Clin North Am Small Anim Pract. 2021;51(2):287-305.