FIV in cats – what can be done? 

What is FIV? 

Feline immunodeficiency virus (FIV) is a cat-specific virus that infects cells of the immune system. This has a negative effect on your pet’s immune function, meaning they are more susceptible to infections than a healthy cat. Once your cat is infected with FIV, they will remain a carrier for the rest of their life. Most individuals will experience a gradual decline in immune function, which can occur over several years. FIV is species-specific, meaning it only affects cats, not people or other animals.  

How is FIV infection spread? 

Infection is usually spread through bite injuries, with the virus passing from the saliva into the bloodstream. Males are at the highest risk of infection, as entire male cats are more likely to fight each other. However, females can also get FIV, sometimes through mating. Males will bite the scruff of a female during this act, which could break the skin and introduce infection. There is also a small risk of FIV-positive females passing on the virus to unborn kittens. 

The virus cannot survive outside of the body for very long, so it is not an infection transmitted on clothing or shared equipment. Some sources suggest that flea bites may be a method of transmission, but research is ongoing.  

Outdoor cats are more likely to run into conflict with other cats than predominantly indoor cats. Incidents of FIV are therefore highest in areas where there are high populations of roaming unneutered cats. 

Unfortunately, there is no vaccination available in the UK for FIV (in some jurisdictions there are vaccines, but their effectiveness and safety are highly contested). However, neutering your cat can decrease the risk of them contracting this illness. Many rescue centres will test their cats before rehoming them so that they can ensure FIV-positive cats are rehomed into suitable adoptive environments. 

Phase 1 –  

This phase occurs 1-3 months after infection, which is known as the acute phase. During this time, the virus travels to the lymph nodes, where it replicates in T-lymphocytes (a type of white blood cell). This viral spread through the lymph nodes causes temporary lymph node enlargement, and affected cats may also have a fever, lethargy and reduced appetite. Often, symptoms are very mild, so this period may go unnoticed altogether.  

Phase 2 –  

Following infection, many cats can be asymptomatic carriers of FIV for some period of time. They may appear to be in good health before their immune system gradually starts to become compromised. This asymptomatic phase can last months to years. During this time, the virus will be replicating very slowly within your cat’s immune system, although your cat won’t show signs of ill health. However, blood work may start to show abnormalities like low white blood cells or increased proteins. Some cats may stay in this latent stage forever, whereas some will progress to the more serious third phase.  

Phase 3 –  

Some cats will become immunocompromised as the virus continues its spread across their immune system. Cats may develop non-specific symptoms such as appetite loss, behavioural changes, weight loss, fever, seizures and stomach upsets may be seen. Secondary diseases can occur in cats with a poor immune system, which could include –  

• Chronic or recurrent infections of the skin, eyes, urinary tract or respiratory tract 

• Inflammation of the gums/mouth and mouth ulcers 

• Cancer 

• Blood disorders 

• Neurological disorders 

Most of the issues we see in FIV-positive cats are related to these secondary diseases and infections rather than the FIV virus itself. An FIV-positive cat is simply unable to fight off bacteria and infections in the normal way that a healthy cat would.  

The severity of these illnesses will vary considerably between patients, but cats that get multiple serious infections or cancer have a poor long-term prognosis.  

How is FIV diagnosed? 

FIV is diagnosed through a blood sample. A blood test screens for the presence of antibodies, which are your cat’s response to invading viruses. A cat with FIV will have raised levels of antibodies, as it is extremely rare for cats to eliminate the virus once it is in their system.  There are two main scenarios for diagnosis – 

• As a screening test performed in a seemingly healthy cat, for example, in a rehoming centre setting, which shows whether a cat is an FIV carrier. 

• A test is recommended by your vet to check for FIV because your cat is unwell.  

Tests can be run ‘patient-side’ within minutes at many vet clinics using an enzyme-linked immunosorbent assay (ELISA) test, though samples can also be sent away to an external laboratory for further confirmation using Western Blot or Immunofluorescence (IFA) assays.  

False negatives may occur if a patient has been tested very soon after contracting FIV, as it can take two to six months for antibodies to develop. In rare cases, a cat in the very late stages of FIV infection may test negative, as their immune system is so compromised that it is no longer able to produce detectable levels of antibodies. 

There is also the possibility of false positives, which can occur in two situations. The first is in young kittens that have an FIV-positive mother. Antibodies are passed to her kittens through her milk. These may be detectable in a blood test. To determine true infection, very young kittens will need repeat testing as they grow older. In some countries, a vaccination is available for FIV, which may lead to a positive antibody result on blood testing. However, in the UK, this scenario is unlikely as we have no commercially available FIV vaccine at the time of writing. 

Are there any treatment options for FIV? 

Unfortunately, there is no cure for FIV in cats. Although long-term prognosis is always guarded, many of these cats can continue to lead a good quality of life with the right care and management, so it is not necessarily a ‘death sentence’. Cats certainly shouldn’t be euthanised on the basis of an FIV positive test alone, especially as some studies show no, or only relatively small, differences in lifespan between infected and non-infected cats. 

Management is aimed at isolating the infected cat to prevent them from spreading the disease but to also limit their exposure to other infections and to protect their compromised immune systems. 

Any medical treatment provided is usually aimed at managing secondary infections and illnesses as they occur. For example, this may be pain relief and dental procedures for cats with gingivitis or anti-inflammatories and antibiotics for cats with respiratory infections. 

There are very few readily available options for treating the actual virus itself. Most drugs trialled have been developed for the treatment of Human Immunodeficiency Virus (HIV). There is still a lot of research to be done in the treatment of FIV in cats, but drugs that have been experimented with include the following examples – 

• Recombinant feline interferon-ω (rIFN-ω; Virbagen Omega; Virbac), which helps to modulate the affected cat’s immunity. This may give an improvement in clinical signs and survival times. 

• Zidovudine (AZT), a nucleoside reverse transcriptase inhibitor, may help cats with severe dental or neurologic disease. However, careful monitoring is needed, and side effects can occur at higher doses. 

• Plerixafor, a selective antagonist of the CXCR4 receptor, to which FIV binds. This drug has been shown to reduce FIV proviral load, but other measurements were less promising. 

For now, many of these drugs (and others trialled) remain too expensive and experimental to be used on a regular basis in general veterinary practice. Plus, we need to be mindful of side effects. However, there are several proactive things that you can do to help take care of an FIV positive cat. 

How do I manage an FIV-positive cat? 

As mentioned, isolating your FIV-positive cat is an important part of managing their condition. But let’s explore what this looks like as well as some of the other key care aspects – 

Isolating infected cats 

Keeping FIV-positive cats away from non-infected cats is crucial. As a responsible pet owner, you will be preventing the spread of this disease to other cats, but also reducing the risk of your cat picking up secondary infections. However, we need to consider your cat’s welfare and mental stimulation in this scenario, as indoor-only cats are less able to carry out natural feline behaviours. 

Battersea Dogs and Cats Home have produced an excellent guide on how you might cat-proof your garden to still be able to provide an enriching outdoor environment for your isolating pet.  If you are unable to provide an outdoor space, then make sure you have considered adaptations inside your home. Lots of hiding spaces, climbing areas, and interactive toys can help keep boredom at bay for indoor pets. 

It may be possible to keep an FIV-positive cat with a non-infected cat, in an already established and stable home set up. If the cats are not fighting, then the infection risk is low, but you may want to take some additional precautions like feeding your pet’s separately and providing plenty of resources to reduce the risk of conflict. Discuss this with your vet, as your well cat’s health and safety need to be considered, and most of the time FIV-positive cats are kept singly. 

Neutering 

Neutering your cat is a good thing to do generally, but especially if they are FIV positive. This reduces fighting and mating tendencies, which may accidentally occur if your cat ever escapes from your home. 

Regular vet checks 

Regular vet check-ups are advised, at least every 6 months. This will help to spot any developing issues like weight loss or dental disease. Blood tests may be recommended intermittently to monitor your cat’s health too. It’s also important to keep on top of regular vaccinations and recommended parasite treatments. to keep your cat as well as possible. 

An appropriate diet 

Keep your cat on a good quality commercial diet, suitable for their age. These are formulated with all the essential nutrients they need for good health. Avoid raw meat, eggs and dairy as your cat is immunocompromised and at increased risk from contracting foodborne illnesses. 

Seek help if your cat appears unwell 

Seeking prompt veterinary treatment if your FIV positive cat seems unwell is vital. This gives your cat a better chance of recovery from any developing secondary illnesses. It’s not uncommon for immunodeficient cats to need longer or more intensive courses of antibiotics and other treatments than an FIV-negative cat would. 

A note on prevention and vaccination 

There is an FIV vaccine licensed for use in some countries, but it is not yet commercially available in the UK. Where used, it currently gives incomplete protection, as there are actually several strains of FIV. There are some reports that if cats who are vaccinated do develop FIV, it may be more aggressive due to antibody dependent enhancement of infection. 

So, at this time, the only ways you can reduce the risk of your cat becoming infected by FIV are by neutering your pet at an early age, keeping up to date with routine flea and worming control, and by considering keeping your cat confined if you live in an area with a large stray cat population.