This type of snap test is used for diagnosing FIV

This week, we saw two cats, both of whom had been strays and both of whom have FIV. One has a terrible mouth: ulcerations, infection, and loose teeth; and the other one looked just like that two weeks ago, before several extractions and two weeks of antibiotics. So, what is it about FIV that leads to all these dental issues?

FIV is the feline immunodeficiency virus, which is quite prevalent in cats that have lived outside for a long while. It is estimated that 15% of sick cats and 2-3% of healthy cats in the US are FIV positive. The virus spreads among cats mainly through bites, as it is present in saliva and blood.  For those of you keeping track, FIV is a lentivirus, like the human immunodeficiency virus (HIV). The FIV virus becomes part of the host cat’s RNA and can never be cleared; so the diagnosis means a life-long infection.

An FIV infection has three possible stages:

  1. Acute: This is a transient stage that begins a few weeks after inoculation with the virus and lasts 3-6 months. It is characterized by fever, enlarged lymph nodes, depression, and possible lack of appetite. The cat may also develop respiratory, oral, or digestive signs during this stage. This stage may go unnoticed by owners.
  2. Latent: Also called the “asymptomatic” stage. These cats appear completely healthy or have only vague clinical signs. On lab work, they show an elevation in their globulin levels as a result of infection. This phase often lasts years.
  3. Terminal: Also called the “chronic” stage. Cats are likely to develop secondary infections like stomatitis (affecting the soft tissues in the mouth), recurrent urinary tract infections, diarrhea, skin infections, and infections in the eye. They are also prone to opportunistic infections from Cryptococcus, Toxoplasma, mycobacteria, and coccidia. This stage can last months to years. The cat is often euthanized due to severe muscle wasting, neurologic issues, or cancers.

Not every cat will have clinical signs matching every stage, so progression of disease is sometimes a guessing game.

Diagnosis: The most common means of diagnosis is a “snap” ELISA test performed on blood in veterinary clinics. A small amount of blood is mixed with an antigen-containing conjugate; if FIV antibodies are present in the blood sample they will bind with the conjugate/antigen to form a complex. The antigen/conjugate/antibody complex triggers a color change in the test device, signaling a positive result. Lack of antibodies in the blood means no color change; this is a negative test result.

Although most veterinarians consider this test to be reliable, two factors can confound a positive result: Kittens may carry maternal FIV antibodies but not be infected; a positive result in a kitten should be rechecked after six months of age. Additionally, cats vaccinated within the past year may be antibody-positive but not infected, causing a false positive. Because there is a moderate rate of false positives, it is generally recommended that a positive result be double-checked using Western blot or immunofluroescence assay (IFA); that said, kittens with maternal antibodies and vaccinated cats will test positive on Western or IFA, too. A negative result, however, is considered very reliable, as false negatives are rare.

Treatment: Little can be done to treat infected cats. Supportive care is provided for any clinical signs, like infections. Positive cats should be kept indoors to avoid continued spread of the infection. They should be vaccinated with only inactivated vaccines, as stimulation of their immune system may enhance viral replication.

Prevention: The current vaccine provides around 50% protection; unfortunately it does not protect against all strains of the virus. Limiting a cat’s interaction with other, possibly positive cats is key to preventing its exposure to this virus.

All cats brought into a home or shelter facility should be tested for FIV. The positive ones will need to be housed separately from the negative ones and the owners or caregivers should know what types of complications to expect. FIV-positive cats have a shorter life expectancy than the average; but, with quality care, they can lead happy and relatively healthy lives.

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