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

By Dr. Duncan Houston, BVSc

Feline Immunodeficiency Virus (FIV) is a significant viral infection affecting cats worldwide. As a retrovirus, FIV compromises the immune system, making cats more susceptible to various infections and diseases. This comprehensive 2025 guide delves into the causes, symptoms, diagnosis, treatment, and prevention of FIV in felines.

Understanding Feline Immunodeficiency Virus 🧬

FIV is a lentivirus that primarily affects domestic cats. It targets the immune system, particularly white blood cells, leading to immunodeficiency. This condition is often compared to HIV in humans due to its similar impact on the immune system, but it's important to note that FIV is species-specific and cannot infect humans.

Prevalence

FIV affects approximately 2.5% to 4.4% of cats worldwide. The prevalence is higher among unneutered male cats with outdoor access, as the virus is commonly transmitted through bite wounds sustained during fights.

Causes of Feline Immunodeficiency Virus 🧬

FIV is primarily transmitted through:

• Bite wounds: The most common mode of transmission, especially among outdoor and unneutered male cats.
• Vertical transmission: From an infected mother to her kittens during birth or through nursing, though this is less common.

Casual contact, such as grooming or sharing food bowls, is unlikely to spread the virus.

Recognizing the Symptoms 🔍

FIV progresses through three stages, each with distinct clinical signs:

1. Acute Phase

• Fever
• Enlarged lymph nodes
• Lethargy
• Loss of appetite

This phase occurs 4–6 weeks post-infection and may be mild or unnoticed.

2. Asymptomatic Phase

Cats may appear healthy for months or years, but the virus continues to replicate, gradually weakening the immune system.

3. Progressive Phase

• Weight loss
• Chronic infections (e.g., skin, respiratory, urinary)
• Gingivitis and stomatitis
• Neurological disorders
• Increased susceptibility to cancers

These symptoms result from the compromised immune system's inability to fight off secondary infections and diseases.

Diagnosis 🩺

Diagnosing FIV involves:

• ELISA (enzyme-linked immunosorbent assay): Detects antibodies against FIV in the blood.
• Western blot or IFA (immunofluorescent antibody assay): Confirmatory tests for FIV antibodies.
• PCR (polymerase chain reaction): Detects FIV DNA, useful in early or ambiguous cases.

It's important to note that kittens may test positive due to maternal antibodies but may not be truly infected. Retesting after six months is recommended.

Treatment Options 💊

There is no cure for FIV, but supportive care can enhance quality of life:

• Regular veterinary check-ups: Monitor health and detect issues early.
• Prompt treatment of secondary infections: Use antibiotics or antivirals as needed.
• Balanced nutrition: Provide a high-quality diet to support the immune system.
• Stress reduction: Maintain a calm environment to minimize stress-induced flare-ups.
• Indoor living: Keep cats indoors to prevent exposure to pathogens and reduce transmission risk.

Some antiviral medications used in human HIV treatment have been explored for FIV, but their efficacy and safety in cats are not well-established.

Prognosis 📈

Many FIV-positive cats live normal lifespans with proper care. The prognosis varies depending on the cat's overall health, the presence of secondary infections, and the stage of the disease at diagnosis.

Preventive Measures 🛡️

Preventing FIV involves:

• Neutering: Reduces fighting behavior, lowering transmission risk.
• Indoor living: Minimizes exposure to infected cats.
• Testing new cats: Screen all new additions to multi-cat households.
• Vaccination: An FIV vaccine exists but is not widely used due to variable efficacy and interference with testing.

Consult your veterinarian to determine the best preventive strategies for your cat.

When to Consult a Veterinarian 👩‍⚕️

Seek veterinary attention if your cat exhibits:

• Persistent fever
• Weight loss
• Chronic infections
• Behavioral changes
• Oral inflammation

Early diagnosis and management are crucial for maintaining your cat's health.

Conclusion 📝

Feline Immunodeficiency Virus is a manageable condition with appropriate care and monitoring. Understanding the disease's progression and implementing preventive measures can help FIV-positive cats lead fulfilling lives. 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. 🐾