FIV in cats
Feline Immunodeficiency Virus or FIV is a virus that infects cells of the immune system, damaging them, or compromising their normal function. This may eventually cause a gradual decline in your cat’s immune system, meaning they struggle to fight off infections that a healthy cat can. In the first few weeks after infection, the virus replicates and may cause mild signs of disease, such as a mild temperature and swollen lymph nodes (glands) - these symptoms may be mild, so they often go unnoticed.
After a period, viral replication increases again in some cats which is when they typically develop signs of disease. This is often around 2-5 years after first becoming infected.
Once a cat has been infected with FIV, the infection is virtually always permanent, and the virus will be present in the saliva of an infected cat. The most common way for the virus to spread from one cat to another is via a cat bite. The virus doesn’t live long in the environment and is easily killed by common disinfectants.
Written by Dr. Mariella Roberts, Veterinary Surgeon, Animal Trust Vets CIC | Published March 2025 | Review date March 2027 | This advice is for UK pets only and is not a replacement for seeing a vet
FIV Symptoms
There are no specific signs associated with FIV, but infected cats often develop recurrent bouts of infections or diseases that gradually get worse over time, and infections may not respond to treatment as well as would normally be expected.
Some of the most common signs seen in FIV-infected cats are:
Weight loss
Fever
Lethargy/tiredness
Enlarged lymph nodes (glands)
Gingivitis and stomatitis (inflammation of the gums and mouth)
Chronic or recurrent breathing, eyes, and guts disease
Chronic skin disease
Nervous system disease (in some cats the virus can affect the brain)
Other diseases may also develop such as cancer (for example, lymphoma) and other infections may cause more of a problem in FIV-infected cats (such as toxoplasmosis).
When to contact your vet
Contact your vet if your cat is showing any of the signs listed above, or if you’re worried your cat has been in contact with an FIV-positive cat.
FIV Diagnosis
FIV can be diagnosed through a simple blood test at your local veterinary clinic that detects antibodies of the virus in the blood. This test is highly reliable, but if there’s any doubt, your vet may also want to send a blood sample off to an external laboratory for additional testing.
FIV Treatment
Unfortunately, cats cannot be cured of FIV, so treatment centre's around managing the other conditions that they might have and keeping them as healthy as possible for as long as possible.
Prevention
Once a cat has FIV, the aim is to keep them healthy and prevent it spreading to other cats. Neutering all FIV-infected cats to reduce the risk of fighting and the spread of infection.
Keeping FIV-positive cats indoors and keeping them away from non-infected cats. This helps prevent the spread of infection to other cats and reduces exposure of the FIV-infected cat to other infections.
Feeding good quality, commercial cat food and avoiding raw meat and eggs that can have pathogens.
Maintaining routine preventive healthcare (regular flea and worm control, routine vaccinations and health checks)
Prompt diagnosis and appropriate treatment of any secondary or concurrent diseases
Living with FIV-positive cats
Managing a household that includes FIV-positive and FIV-negative cats can get complicated. Ideally, the two groups would be completely separated, but if that isn’t possible and they don’t usually fight, giving them separate water and food bowls may be sufficient.
Outlook
The prognosis for cats infected with FIV depends on the disease's progression. Early diagnosis can lead to a prolonged period without symptoms. Not all infected cats will develop immunodeficiency syndrome. Sadly, cats with secondary infections may succumb to them or require euthanasia.