Feline Leukemia

Feline Leukemia


Introduction: Despite the widespread use of vaccines, feline leukemia virus (FeLV) remains one of the most important causes of disease and death in cats.













This disease causes a variety of problems:

1.  Cats that don't act sick at all, but carry and spread the virus around to other cats.  It's estimated that about 2% of all healthy looking stray cats in the USA are carriers and spreaders of leukemia virus.

2.  Cats that are deathly ill with multiple symptoms and end up dying soon after getting sick.  Common problems caused by the leukemia virus include fevers, weight loss, abortions, severe diarrhea, severe respiratory diseases, and anemia.

3.  Cats that develop cancer and die slowly over a period of months.

4.  And maybe most common of all ... the disease weakens the cat's immune symstem ... somewhat like human AIDS disease...  making the cat susceptible to colds, respiratory infections, pneumonia, bowel infections, eye infections, wounds that won't heal normally.  A miserable life.












The virus is present worldwide.

It is mostly a disease of young cats.

It is more common in outdoor cats, in households with multiple cats, and in catteries and where ever cats live in groups such as dairy barns, horse barns and so forth.

The disease is spread by the saliva, the urine, the feces, the tears, and through bite wounds.
Kittens can get the virus from their mother while in the uterus or while nursing.

Diagnosis:  We now have reliable test kits in our clinics that test for leukemia as well as Feline AIDS.

These test kits are easy, reliable, inexpensive, and NOT affected by vaccinations.  But they aren't perfect.  Here are some rules of thumb:

If a patient is very ill and the test comes up positive, we assume the test kit is correct and depending on how ill the patient is give a very poor prognosis and frequently recommend euthanasia.

But if the patient isn't ill and the test comes up positive ... a frequent occurence when someone brings in a newly found stray cat for a check up ...  we either confirm the result by sending blood into a commercial lab (which will use a different type of test) OR we'll retest again in about 1 month because many cats that have had recent exposure to the virus will test positive but will successfully fight off the disease and have a negative test result a month later.

There is also a small chance of a false negative result in those situations where a cat was tested in the first few weeks after exposure before the virus had time to replicate enough to make the test positive.  This is why a negative test is unreliable in kittens under 9 weeks of age.









Prevention: Vaccination has been very successful.  As a young vet, I helplessly watched or humanely euthanized hundreds of cats die from this diseas each year.  Now, I still see several cases a month, but almost exclusively in non-vaccinated cats and strays.

You may already know that there has been quite some controversy over the safety of leukemia vaccine and another controversy about whether or not we are  vaccinating middle aged and older cats unneccessarily.

As to the first issue of vaccine safety, evidence is pretty conclusive that a small percentage of cats (less than 1 in 10,000 is the most common estimate) developed cancer as a result of the vaccine.
That problem has recently been fixed ... the new "sub unit" or adjuvant free vaccines now available for leukemia and rabies are safer, more effective, and don't cause cancer.  At present, they are a little more expensive.

As to the second issue of when to vaccinate?  We vets are near unanimous agreement that it's important to vaccinate kittens twice about 3-4 weeks apart .  I like to recommend the vaccine at 8-10 weeks of age and then again a month later.  Most of us agree that young cats should be revaccinated yearly at 1 and 2 years of age.  After that, we argue.  2 vets in the room.  3 points of view.

In general, we recommend annual revaccination for outdoor cats, multi-cat households, catteries, and other cats at higher risk, but typically vaccinate less often 100% indoor cats and senior cats.

Treatment:

We can treat the secondary diseases that leukemia positive patients are so prone to, such as diarrhea, respiratory infections, eye infections, and so forth.

We can give supportive care and supplemental care such as IV fluids, immune stimulants, anti-oxidants, vitamin cocktails, and so forth.

But, as of yet, there isn't a cure for the disease ... a treatment that eliminates the virus from the body.

Not that veterinary scientists and pharmacists haven't tried various antiviral drugs and treatments.  A lot of time and money has been devoted to conquering this disease.