Feline Leukemia Virus (FeLV) in Cats 🧬🐱

By Dr Duncan Houston, BVSc

Feline leukemia virus (FeLV) is one of the most serious viral diseases affecting cats. This retrovirus is a leading cause of feline illness and death. Yet, with proper testing, vaccination, and home care, FeLV can be prevented—or managed in positive cats. 🛡️

🦠 What Is FeLV?

FeLV is a retrovirus that attacks a cat’s immune system and bone marrow. It spreads primarily through saliva, urine, and nasal secretions—especially during close contact like grooming, sharing bowls, or bite wounds. 🦷

Other transmission routes include:

• 🐾 Contaminated litter or water bowls
• 👶 In utero infection from pregnant queens
• 🍼 Infected milk during nursing
• 💉 Blood transfusions or unsterile instruments

🧬 Four Infection Types

1. Abortive – Immune system clears virus completely 🛡️
2. Regressive – Virus suppressed but may remain in low numbers (PCR+)
3. Latent – Virus hides in tissues, PCR+ but non-contagious unless reactivated
4. Progressive – Active virus replication, antigen-positive, and contagious ⚠️

📋 Signs & Symptoms

FeLV causes many different syndromes depending on what tissues are affected. It may be silent for months or years. Look for:

• 🦠 Lymphoma or leukemia
• 🧠 Neurologic issues (behavior, paralysis, seizures)
• 🩸 Blood disorders (anemia, bone marrow suppression)
• 😷 Chronic respiratory infections
• 💛 Jaundice or liver disease
• 🐾 Enlarged lymph nodes, spleen, or kidneys
• 👁️ Uveitis (eye inflammation)
• 🐱 Failure to thrive, fading kitten syndrome

If your cat isn’t improving with usual treatments, FeLV may be affecting recovery. 🩺

🧪 Diagnostic Testing

• 💉 In-house ELISA tests screen for FeLV antigen
• 🧬 PCR testing confirms regressive or latent infections
• 🩸 Bloodwork, radiographs, and bone marrow biopsies help assess damage

Always test new cats or kittens before adoption. Retest 90+ days post-exposure for accuracy. 🔬

💊 Treatment Options

There is no cure for FeLV. Treatment focuses on supporting the immune system and managing secondary infections.

Supportive therapies may include:

• 💉 Blood transfusions
• 🧬 Antivirals, immunomodulators
• 💊 Prednisone or other corticosteroids
• 🦠 Antibiotics for infections
• 💪 Nutritional and fluid support

📈 Prognosis

FeLV+ cats may live months to several years. Prognosis depends on the infection type and access to supportive care. Sadly, most persistently infected cats in multi-cat homes die within three years of diagnosis. 🖤

🛡️ Prevention Strategies

1. 💉 Vaccination

• 🐱 Vaccinate kittens at 8–9 weeks old, booster in 3–4 weeks
• 📅 Yearly booster if high-risk (outdoor cats)
• 🧬 FeLV vaccines won’t help infected cats, but protect healthy ones

2. 🧪 Regular Testing

• 📋 Test all new cats before introduction
• 📆 Retest after known or suspected exposure

3. 🚫 Closed Colonies

• 🐾 Avoid adding new cats to FeLV+ households
• 🏠 Keep infected cats indoors only

🧼 Environmental Safety

FeLV is a fragile virus—it dies quickly outside the body and is easily destroyed by disinfectants. New cats can safely enter a previously “contaminated” home within a few days. 🧴

👨‍⚕️ Human Risk?

FeLV does not infect humans. Despite its name and viral similarity, no human infection has ever been documented. 🧍‍♂️✅

📱 Ask A Vet App Support

Worried about FeLV exposure or managing a positive cat? The Ask A Vet app offers:

• 🧬 Interpretation of FeLV test results
• 📋 Vaccine schedules and retest reminders
• 💬 Expert help managing immune support and home setup
• 📊 Ongoing care tracking for positive cats

🏁 Final Takeaway

FeLV is preventable but serious. Vaccination, early testing, and isolating infected cats are your best tools. If your cat is FeLV+, compassionate home care and regular monitoring can still offer good quality of life. For guidance every step of the way, use the Ask A Vet app. 🐱❤️