FELINE IMMUNODEFICIENCY VIRUS (FIV)
Introduction
Feline Immunodeficiency Virus (FIV) was first recognised in California in 1968
and in the UK in 1975, but it has probably existed in the cat population for
much longer. It may be mistakenly confused with the Human
Immunodeficiency Virus (HIV), just because it sounds the same but it is, in
reality, a distinctly different virus, correctly termed a virion. As a result there is
no evidence that human beings or any other species can become infected
with FIV.
What is Feline Immunodeficiency Virus?
FIV is a retrovirus; that means the virion can enter a body cell and order the
cell to create a copy of itself. It is a significant cause of disease in cats
worldwide.
Infection in Cats
FIV is rare in cats less than one year of age, unlike feline leukaemia virus
infections, which are usually caught when young. It is commoner in male cats
and particularly in those that roam free. This is a reflection of their tendency to
fight and it is fighting with the chance for blood and saliva to be passed from
one cat to another that is the main means of transmission.
Farm and feral cats, as well as pedigree show cats, are highest on the list of
the infected – highlighting the strong association of infection with access to an
outdoor environment and the congregation of cats under one roof.
FIV is known to be present in the blood, saliva and cerebrospinal fluid of
infected cats. However, the virus is extremely fragile and does not survive
outside the cat’s body. Most FIV-positive cats have a history of catfights and
bite-wound abscesses.
Pet Health Council – Feline Immunodeficiency Virus – Updated November 2004
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Source of Infection in Cats
The main method of transmission of FIV from one cat to another is through a
bite wound during a catfight. The virus is rarely spread through casual cat-tocat contact, but cannot be ruled out. However, female cats infected with FIV
during their pregnancy can pass the virus to their unborn kittens. There is no
evidence so far for sexual transmission.
Male cats are twice as likely as female cats to be infected with FIV. This
reflects the greater tendency of male cats (especially those who are not
neutered) to roam and fight with other cats. Outdoor, free-roaming cats are
more likely to contract FIV than indoor cats. The incubation period of the virus
appears to be lengthy, perhaps two to five years before the characteristic
signs of immuno-deficiency disease (feline ‘AIDS’) show.
Disease in Cats
The occurrence of feline AIDS – the disease – is dependant on a number of
factors such as the dose of virion transmitted, the age at the time of infection,
the route of infection and the potential for the variation in the degree of
virulence of the virion.
The virion can manifest itself as a primary disease with a raised temperature
and lymph node swellings. Once into remission, any further signs may be
delayed for months or years. These will relate to the failure of the cat’s
immune system to protect it from secondary infections and inappropriate
responses by the antibody system. The list of signs is very long, but most
common are the infections of the oral cavity, the intestines and the respiratory
system. Mouth ulcers, diarrhoea and lung infections can be joined by an
increased incidence of tumours.
Eventual decline and whole body system failures are the common sequel, but
some are very chronic and the animals go for months or years into terminal
illness.
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Diagnosis in Cats
When a cat becomes infected with FIV, there may be no clinical signs for
many years. However, it is known that four to six weeks after infection the
white blood cell count declines and some cats will have swollen lymph nodes.
Some cats can have fever, anaemia, or diarrhoea at this early stage. FIV is
toxic to a type of white blood cell, the T-helper cell, which is critical for an
effective immune system.
FIV is diagnosed by using a blood test, which detects antibodies against the
virus in the bloodstream of the cat. More advanced tests may look for the
presence of the virus, otherwise known as detection of viral antigen, viral RNA
or the detection of the virion itself. Vets commonly test cats for FIV as well as
for feline leukaemia virus at the same time if there are unexplained chronic
symptoms of disease in a major body system.
Treatment and Prevention in Cats
Therapy of the secondary infections associated with FIV is based on the
clinical signs and the nature of the infectious agent. Symptomatic treatment
of these cats is indicated, but always with the caution that eventually little can
be done to stem the inevitable collapse of the cat’s immune system. Once
identified a positive result to FIV testing must carry a very guarded prognosis.
No vaccine is available to prevent FIV infections. Owners can protect their
cats only by preventing them from contacting infected cats. Pets kept indoors
and away from free-roaming cats are unlikely to contract FIV infection.
FIV and Humans
Although FIV is similar structurally to HIV and causes a disease in cats similar
to AIDS in humans, it is a highly species-specific agent. Initial studies indicate
that vets, owners and researchers who have had close contact with FIV
infected cats show absolutely no evidence of FIV infection. It appears at this
time that FIV infections are restricted solely to cats.
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However, immuno-suppressed humans, the elderly or the very young may
catch some of the secondary infections associated with FIV positive cats.
Conclusion
As with humans, cats may harbour FIV for many years prior to developing any
signs. There is no reason why healthy FIV-positive cats or those in the early
stages of the disease need to be euthanised as long as they are not suffering
in any way or are putting other cats at risk. There is no evidence that human
beings or any other species can become infected by FIV.
Pets are Good for People
Pets provide us with loyalty, companionship, love and affection, as well as the
many physical and psychological benefits. The least we can do to repay this
is to ensure that we keep them in the best of health. A healthy pet is a happy
pet and a happy pet can help us enjoy a much fuller and more rewarding life.
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For further information, please contact the Pet Health Council on:
Telephone: 020 7255 5408
Email: phc@uk.grayling.com
Website: www.pethealthcouncil.co.uk
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