Feline Leukemia Virus (FeLV): A 2025 Veterinary Guide to Causes, Symptoms & Treatment 🐱🧬

By Dr. Duncan Houston, BVSc

Feline Leukemia Virus (FeLV) is a significant viral infection affecting cats worldwide. As a retrovirus, FeLV integrates into the host's DNA, leading to various health issues, including immunosuppression, anemia, and cancer. This comprehensive 2025 guide delves into the causes, symptoms, diagnosis, treatment, and prevention of FeLV in felines.

Understanding Feline Leukemia Virus 🧬

FeLV is a gammaretrovirus that primarily affects domestic cats. It compromises the immune system, making cats more susceptible to infections and certain types of cancer, such as lymphoma and leukemia. The virus is transmitted through close contact, often via saliva, nasal secretions, urine, feces, and milk from infected cats.

Prevalence

FeLV affects approximately 2-3% of cats in the United States and Canada. The prevalence is higher among cats that are young, unvaccinated, or have outdoor access, especially those living in multi-cat households or shelters.

Causes of Feline Leukemia Virus 🧬

FeLV is transmitted primarily through:

• Saliva and nasal secretions: Mutual grooming or bite wounds.
• Urine and feces: Shared litter boxes.
• Milk: Nursing from an infected mother.
• In utero: Transmission from an infected queen to her kittens.

Cats at higher risk include:

• Unvaccinated cats.
• Cats with outdoor access.
• Cats in multi-cat environments.
• Kittens and young cats.

Recognizing the Symptoms 🔍

FeLV can cause a variety of clinical signs, which may develop gradually:

• Persistent fever
• Lethargy and weakness
• Loss of appetite and weight loss
• Pale gums (anemia)
• Enlarged lymph nodes
• Recurring infections
• Diarrhea
• Neurological disorders
• Reproductive problems

Some cats may remain asymptomatic for extended periods, making regular testing crucial.

Diagnosis 🩺

Diagnosing FeLV involves:

• ELISA (enzyme-linked immunosorbent assay): Detects FeLV antigens in the blood.
• IFA (immunofluorescent antibody assay): Confirms infection by detecting viral proteins in white blood cells.
• PCR (polymerase chain reaction): Identifies viral DNA in the blood.

It's recommended to retest positive cats after 12 weeks to confirm persistent infection, as some cats may clear the virus naturally.

Treatment Options 💊

There is no cure for FeLV, but supportive care can improve quality of life:

• Regular veterinary check-ups: Monitor health and detect complications early.
• Balanced nutrition: High-quality diet to support the immune system.
• Stress reduction: Provide a calm environment to minimize stress-induced flare-ups.
• Prompt treatment of secondary infections: Use antibiotics or antivirals as needed.
• Management of anemia: May require blood transfusions or medications.

FeLV-positive cats should be kept indoors to prevent spreading the virus to other cats.

Prognosis 📈

The prognosis for FeLV-infected cats varies:

• Asymptomatic cats: May live for several years without clinical signs.
• Symptomatic cats: Median survival time is approximately 2.5 years after diagnosis.

Early detection and supportive care can enhance longevity and quality of life.

Preventive Measures 🛡️

Preventing FeLV involves:

• Vaccination: Effective vaccines are available and recommended for at-risk cats.
• Testing new cats: Test all new additions to multi-cat households before introduction.
• Indoor living: Keep cats indoors to reduce exposure to infected cats.
• Regular veterinary visits: Annual check-ups and vaccinations.

Discuss with your veterinarian whether the FeLV vaccine is appropriate for your cat's lifestyle.

When to Consult a Veterinarian 👩‍⚕️

Seek veterinary attention if your cat exhibits:

• Persistent fever
• Unexplained weight loss
• Lethargy or weakness
• Recurring infections
• Enlarged lymph nodes

Early diagnosis and management are key to improving outcomes.

Conclusion 📝

Feline Leukemia Virus is a serious condition, but with proper preventive measures and supportive care, affected cats can lead comfortable lives. Regular veterinary care, vaccination, and minimizing exposure to infected cats are essential strategies. For personalized advice and support, consider reaching out to veterinary professionals through platforms like Ask A Vet. Their expertise can guide you through diagnosis, treatment options, and ongoing care tailored to your cat's specific needs.

Stay proactive in your cat's health to ensure a happy and healthy life together. 🐾