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Frito liked to eat. Living on the streets of Brooklyn, New
York as a feral cat, food was a scarce commodity. Although a cautious
and timid tomcat by nature, Lois Stein patiently gained Frito’s trust
using a few kind words…and lot of tuna! In a few short weeks, Lois, a
lifelong cat lover, was able to pat him and scratch his head,
distracting him with her armament of snacks and treats, which he
devoured ravenously. An unneutered male, Frito had the big jowls
eventually develop in testosterone-laden tomcats, and his scarred and
scabby head bore the evidence of past catfights. But underneath his
gruff exterior, Frito was a housecat at heart, and it didn’t take very
long before Lois could lure him into a cat carrier and bring him inside.
Once captured, Lois let Frito acclimate to her one-bedroom
apartment. He quickly took to sleeping on the bed, and learned to use
his litter box immediately. A week later, Lois figured it was time for
Frito’s first trip to the vet. Frito was pronounced healthy. He was
tested for the feline leukemia virus, and vaccinated against
panleukopenia, the upper respiratory viruses, and rabies. He was
neutered two weeks after that. Frito’s veterinarian estimated his age to
be between 3 and 5 years.
Frito quickly
settled into a life of domestic bliss, becoming friendly, outgoing, and
affectionate. He seemed to have lost all traces of his former feral
life, except one: his appetite. Although food was now abundant, Frito
attacked his food bowl as if each meal was his last. Gluttony
notwithstanding, Frito lived on for years as a happy (if not somewhat
beefy) companion. So, when Frito stopped eating last week, Lois knew
something was amiss.
“He was interested in the food, but he
wouldn’t eat it. He’d try, but the pieces would fall out of his mouth.
He’d only eat canned food, and even then, it was obvious something was
bothering him”.
As a veterinarian specializing in cats, I
had seen countless cases of cats that have stopped eating. But this was
different. Frito wanted to eat, but couldn’t. This usually indicates an
oral problem.
On
physical exam, Frito was friendly and cooperative. Oral examination
revealed several abnormalities, most notably a large ulcer in the center
of his tongue, and a smaller one on the tip. Frito also had significant
dental tartar and gingivitis. Assured that he could not have ingested a
caustic substance, I probed a bit further. I asked about his feline
leukemia (FeLV) and feline immunodeficiency virus (FIV) status. FIV is
known to cause oral problems in cats, especially oral ulcers. Lois
showed me Frito’s medical records. I saw that his original veterinarian
had tested him for FeLV five years previously, but there was no record
of an FIV test. Knowing that this virus is transmitted by bite wounds,
and seeing all of Frito’s battle scars, I feared the worst. Obtaining
blood for a combination FeLV/FIV test, I ran the test immediately.
Eight minutes later, I had sad news to report: Frito tested positive
for FIV. Lois was distraught, and she peppered me with questions. “Why
wasn’t he tested when I found him years ago?! How could I have
prevented this?!” Lois grew quiet. “So… what do we do now?” she sighed.
The
feline immunodeficiency virus was isolated by Dr. Neils Pedersen and Dr.
Janet Yamamoto in 1986 from a cat with clinical symptoms that were
strikingly similar to those seen in humans with acquired
immunodeficiency syndrome (AIDS),
the disease associated with human immunodeficiency virus (HIV)
infection. FIV and HIV are classified as retroviruses. They contain RNA
as their genetic material. Once the virus invades the host’s cells, it
uses the cell’s own machinery to make a DNA copy of its genome. The
viral DNA is then incorporated into the host’s own genome, where it
serves as a template to reproduce thousands of copies of itself.
Despite the similarities to the human immunodeficiency virus, FIV cannot
be transmitted to humans.
Fighting is the primary mode of viral transmission. The virus is
present in saliva, and infected cats can transmit the virus by biting
other cats. As free-roaming, intact male cats are more likely to engage
in fighting behavior, the disease has the highest prevalence in this
population of cats. Frito, having lived out doors and bearing the scars
of numerous catfights, was a textbook case.
FIV
infection can be divided into three stages: acute infection, lasting 3
to 6 months; subclinical infection, lasting months to years; and feline
AIDS or chronic clinical disease, which may also last months or years.
Cats in the first (acute) stage of infection experience mild disease
(fever, lymph node enlargement, intermittent lethargy and decreased
appetite). Most cats recover on their own, and are rarely presented for
veterinary care in this stage. During the subclinical stage, cats
remain clinically healthy, although their immune function continues to
deteriorate, as the virus causes a continuous decline in CD4+ cells –
white blood cells important for proper immune function. As their CD4+
cells reach very low levels, the third stage of disease develops, and
cats show signs of their illness. These cats are susceptible to a wide
variety of opportunistic diseases. (See Sidebar One). Oral problems are
a common manifestation of FIV infection. Other common diseases seen in
FIV infection include recurrent upper respiratory infections, chronic
gastrointestinal disorders, and chronic skin disorders. Frito presented
in this later stage of FIV infection.
The American
Association of Feline Practitioners and the Academy of Feline Medicine
regularly publishes guidelines for feline retrovirus testing and
management. In their latest report, they once again recommended testing
all cats for FIV, especially under certain circumstances.
Once
a diagnosis is made, several steps should be taken. No test is 100%
accurate at all times and under all conditions. Positive test results,
especially in cats with no symptoms, should be confirmed with a test
known as a Western Blot test. A diagnosis of FIV is not necessarily an
automatic death sentence. Cats can live a healthy, normal life for
years before symptoms of disease become apparent. Other cats in the
household are theoretically at risk, however, the virus is transmitted
by bite wounds. Casual contact (mutual grooming, sharing of food bowls,
water bowls, and litter boxes) does not transmit the disease. As most
cats in a multiple-cat household live together peacefully, transmission
to the other cats is not very likely. Dr. Anne Sinclair, president and
CEO of Cat Sense Feline Hospital and Boarding, Inc. in Bel Air,
Maryland, agrees. “I’ve been examining six cats in a multiple cat
household, two of which are FIV positive”, she says. “I’ve been testing
all six cats every year. The FIV status has remained the same for the
past eight years now”. Cats with FIV should remain indoors permanently,
to prevent spread to other cats, as well as to limit their exposure to
infectious agents carried by other animals. Owners of FIV-infected cats
need to be vigilant, and should bring their cat to the veterinarian at
the first sign that something might be amiss. Early recognition and
aggressive treatment is important in the care of these cats.
Semi-annual wellness visits are a must.
Treatment of the viral infection itself is somewhat limited. Therapy
for retroviruses has focused on inhibiting reverse transcriptase, the
enzyme that catalyzes the production of viral DNA. Therapy with drugs
that have been used to treat HIV, such as AZT (azothiouridine) has been
attempted in cats, with mixed results. Anti-retroviral drugs seem most
effective when given early in the course of disease. This is a problem,
since the acute stage of disease tends to be missed by most cat owners.
To date, there is no treatment that has been shown to reverse
well-established FIV infections in cats. Given this fact, the care of
FIV-infected cats is mainly supportive. Fortunately, many cats infected
with FIV respond as well as their unifected counterparts to appropriate
medications and treatments, although a longer or more aggressive course
of treatment is often needed. Infectious conditions require
antimicrobial therapy. Inflammatory conditions may require therapy with
systemic anti-inflammatory drugs, such as corticosteroids.
In
terms of disease prevention, for years the only truly effective advice
we could give our clients was to have owners keep their FIV-negative
cats indoors where they could not encounter infected cats. Cats that do
go outdoors should be spayed and neutered, to limit the spread of FIV by
decreasing fighting and roaming behavior. Recently, however, a major
scientific breakthrough may significantly change the way we prevent FIV
infection.
In 2004, the U.S.
Department of Agriculture approved the
first vaccine against FIV. The vaccine has been licensed to Fort Dodge
Animal Health, of Overland, Kansas. Dr. Janet Yamamoto, Professor of Pathobiology at the University of Florida in Gainesville, worked with
researchers at Fort Dodge Animal Health for more than a decade to
develop the vaccine. "The
vaccine offers the first effective protection for cats against this
often fatal disease”, says Neils Pedersen, co-discoverer of the virus
and Professor and Director of the Center for Companion Animal Health at
the University of California at Davis. Cats determined to be at risk for
the disease will initially require a series of three vaccines, given
approximately three weeks apart, to achieve immunity. Annual boosters
are recommended thereafter. Dr. Steve Connell, Director of Professional
Services at Fort Dodge Animal Health, says that no major side effects or
adverse reactions were seen in the safety study, in which 600 cats were
vaccinated. There is some concern about the vaccine’s effectiveness,
however. In a study of the vaccine’s efficacy, 67% of cats vaccinated
against FIV were protected from infection when exposed to the virus. In
comparison, of 100 non-vaccinated cats exposed to FIV, 76% contracted
the disease. This calculates out to a 55% “positive predictive value”.
The positive predictive value is a better reflection of a vaccine’s true
effectiveness, and a 55% protection is considered to be somewhat low.
(Rabies vaccination, in comparison, approaches nearly 100% protection).
Another concern centers around future FIV testing. The current FIV test
is designed to detect antibodies against the virus. Cats vaccinated
against FIV will develop antibodies against the virus. It may not be
possible to determine, in vaccinated cats who might develop symptoms of
FIV infection months or years later, whether the antibodies in their
bloodstream developed in response to previous vaccination, or in
response to natural infection. “We feel the benefits outweigh the
negatives in terms of testing.” He continues, “Similar concerns were
expressed when the Lyme disease vaccine was initially introduced. Soon
after, however, the Western Blot test was shown to be able to
distinguish whether antibodies were due to vaccination vs. infection.
We feel confident that the testing issue will be a non-issue”.
“Fort Dodge
strongly urges all clients to have their cats tested before considering
vaccination, because cats already carrying the virus will not benefit at
all from vaccination.”
Dr.
Jack Bregman, owner of two feline-exclusive veterinary hospitals in New
York, is elated with the new vaccine. “I examine hundreds of cats every
year. I diagnose a case of FIV at least once a month, and I euthanize
more sick FIV-positive cats than I care to think about. I hope the
vaccine reduces the incidence in the same way the feline leukemia virus
vaccine did when it hit the market several years ago.” The development
of the vaccine is significant in another aspect as well: FIV has been
studied extensively because researchers feel that it serves as a useful
animal model for the study of HIV in humans. The development of a
vaccine against FIV fuels the hope that a human vaccine is possible.
Frito
is doing well now. A brief course of antibiotics to prevent secondary
oral bacterial infection, and two weeks of a liquefied diet has caused
his oral ulcers to heal. “He’s started crunching on his dry food
again,” says Lois, relieved. “I hope to keep Frito around for a long
time”.
Organ systems
commonly affected by FIV:
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Oral Cavity:
dental and gum disease, lingual (tongue) ulcers
-
Lymph nodes:
enlargement is commonly seen
-
Eyes: eye
infections and retinal disorders
-
Skin: external
parasites, as well as fungal infections, such as ringworm, commonly
develop
-
Body weight:
should be accurately measured and recorded, because weight loss is
often the first sign of deterioration in a cat’s condition
FIV testing
guidelines, as recommended by the American Association of Feline
Practitioners and the Academy of Feline Medicine.
All cats should be
tested for FIV in the following circumstances:
-
when cats are
sick, regardless of previous negative test results
-
when cats and
kittens, regardless of age, are newly adopted, whether or not they
will be entering a household with other cats
-
when cats live
in households containing cats with unknown FIV infection status
-
when cats have
had potential exposure, such as a bite inflicted by a cat of unknown
infection status. Such cats should be tested a minimum of 60 days
post-exposure
-
every year, if
cats are at high risk of infection (high risk = cats that fight, or
those that live with infected cats)
Updated 2/9/06
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