Monday, May 18, 2015

Feline Immunodeficiency Virus (FIV): Frequently Asked Questions

Blanco, a 15 year old FIV-positive cat

Is this the same virus that causes AIDS in people?

No. The Feline Immunodeficiency Virus (FIV) is also sometimes called the Feline AIDS Virus.  It is likened to the Human Immunodeficiency Virus (HIV) that affects people because of the similarities in the two diseases which result.  Fortunately, most viruses are species specific.  This is the case with HIV and FIV.  The Human Immunodeficiency Virus only affects humans, and the Feline Immunodeficiency Virus only affects cats.

FIV is a type of retrovirus called a "lentivirus" (slow virus) that attacks many of the cells of the
immune system, leaving the cat at risk for diseases that a healthy immune system can usually fight. Once infected, the virus takes up residence in a cat's lymph nodes and infects T-lymphocytes. Sometimes, the lymph nodes can become enlarged tempporarily as the virus spreads to other lymph nodes.

How do cats get FIV?

FIV is transmitted primarily by biting that usually accompanies cat fights.  Other interactions of cats,
such as sharing common food and water bowls or grooming each other, have not been shown to be significant in transmission. FIV affects up to 3% of the healthy cat population in any given area, and is much higher in populations of high-risk or ill cats. In some cases, isolated stray or feral colonies my have up to 100% of the population infected but apparently healthy. Male cats, especially intact males, are at highest risk for disease as they are more likely to fight and spread the virus.

How is it diagnosed?

Evidence of exposure to FIV can be detected by a simple blood test.  A positive test means the cat has been exposed to the virus and will likely be infected for the remainder of its life.  A negative may mean that the cat has not been exposed; however, false negatives occur in two situations:

1.         From the time of initial virus inoculation into the cat, it may take up to two years for the test to turn positive.  Therefore, for up to two years, the test may be negative even though the virus is present in the cat.

2.         When some cats become terminally ill with FIV, the test may again turn negative.  This occurs because antibodies (immune proteins) produced against the virus become attached and bound to the large amount of virus present.  Since the test detects antibodies which are free in circulation, the test may be falsely negative.   This is not the normal occurrence, but it does happen to some cats.

What does a positive test result mean in a kitten?

The vast majority of kittens under 4 months of age who test positive have not been exposed to the virus.  Instead, the test is detecting the immunity (antibodies) that were passed from the mother to the kitten.  These antibodies may persist until the kitten is about 6 months old.  Therefore, the kitten should be retested at about 6 months of age.  If it remains positive, the possibility of true infection is much greater.  If the kitten tests negative, there is nothing to worry about.

How can a kitten become infected?

If a kitten is bitten by an FIV infected cat, it can develop a true infection.  However, the test will usually not turn positive for many months.  If a mother cat is infected with the FIV at the time she is pregnant or nursing, she can pass large quantities of the virus to her kittens.  This means of transmission may result in a positive test result in just a few weeks. 

What type of disease does the FIV cause?

An FIV infected cat will generally go through a prolonged period of normal life with normal risk for health issues (viral dormancy) before it becomes ill.  This incubation period may last 6-8 years or more.  Thus, we generally do not diagnosis an FIV sick cat at an early age.

When illness occurs, we usually see a variety of severe chronic illnesses. This is because the cat's immune system becomes weakened and can no longer fight off the normal bacteria, viruses, fungi and protozoa that a healthy immune system would easily eliminate from the body. The most common illness is a severe infection affecting the gums.  Abscesses from fight wounds that should heal within a week or two may remain active for several months.  Respiratory infections may linger for weeks.  The cat may lose weight and go through periods of not eating well; the hair coat may become unkempt.  The cat may have episodes of treatment-resistant diarrhea.  Ultimately, widespread organ failure occurs, and the cat dies.

What are the signs of an active FIV infection?

  • Poor coat
  • Persistent fever
  • Poor appetite
  • Poor oral health - gingivitis, stomatitis, dental abscesses
  • Chronic, persistent or recurrent infections of the skin, respiratory system or bladder
  • Weight loss
  • Cancer and blood diseases
  • Reproductive failure
  • Seizures, behavior changes, neurological disorders

Is there a treatment for it?

There is no treatment that will rid the cat of FIV.  Sometimes, the disease state can be treated and the cat experiences a period of recovery and relatively good health.  However, the virus will still be in the cat and may become active at a later date.  Therefore, the long term prognosis is not good.

What should I do with a cat that is FIV positive but is not ill?

If you have a cat that tests FIV positive but is not ill, it is not necessary to euthanize it immediately.  As long as it does not fight with your other cats or those of your neighbors, transmission is not likely to occur.  However, if it is prone to fight or if another cat often instigates fights with it, transmission is likely.  In fairness to your neighbors, it is generally recommended to prevent an FIV positive cat from roaming the neighborhood. Owners of infected cats must be responsible so that the likelihood of transmission to someone else's cat is minimized. Additionally, living an indoor life will reduce the positive cat's exposure to communicable diseases, parasites and other infectious agents that are common in the outdoor environment.

Wellness visits should be scheduled every 6 months, and you should keep a close eye on your FIV positive cat's weight, since weight loss is often the first sign that a cat is feeling ill.

FIV is not a contraindication for spay and neuter surgeries. 

Cats that are FIV positive should not eat a raw diet or unpasteurized dairy.  Food borne illnesses or parasites that a healthy cat is likely able to fight off are a higher risk for immunosuppressed cats.

There is a growing body of research into anti-viral therapies, but so far, no therapy stands out as a conclusive benefit to the health and longevity of FIV positive cats.

If an FIV positive cat has spent a period of time in your house, you will want to use normal cleaning and disinfecting methods to sanitize the area where the cat lived. FIV does not last long outside the body of a cat, however any secondary infections - bacterial, viral, fungal or protozoal, may linger on food dishes, bedding, litter pans and toys. A dilute bleach solution should be sufficient to clean these items.

For a little more information about one of our patient who is currently a 15 year old FIV survivor, you can read about Blanco on our blog!

Is there a vaccine for FIV?

Unfortunately, there is not a recommended vaccine available for FIV. Vaccination with the currently available FIV vaccine will cause your cat to test positive on an FIV test.

When should FIV testing be performed?

As a general rule, it takes 8-12 weeks for antibodies to appear after infection, so a post-exposure test should be performed a minimum of 60 days after a known exposure, such as a bite wound from an unknown animal. The antibody test is the standard initial screening test, and can be performed in the veterinary office within a few minutes. However, if the test is positive, it is generally recommended to confirm the test using an alternate method. In the past, the Western Blot test has always been the gold standard of confirmation testing, however, PCR tests are extremely sensitive (possibly too sensitive at this time?) and are showing promise as a superior testing method. 
  • Sick cats
  • Untested cats, or cats with an uncertain history of testing
  • Newly adopted cats
  • After a possible exposure (escaping out of the house with or without an obvious bite wound, living in a house with cats with unknown FIV status or uncertain testing history)
  • After definite exposure (spending time in the vicinity of a positive cat with or without a bite wound) 
Additional Resources:

Oral Health-Retrovirus Connection

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