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Feline Leukemia... FeLV

Here's another scourge of cats that makes cat lovers shiver with dread. Feline Leukemia Virus is another retrovirus, similar to the retroviruses FIV (specific to cats) and AIDS (specific to humans).

What is the feline leukemia retrovirus?
Retroviruses produce an enzyme called 'reverse transcriptase'. This enzyme has the unique property of allowing the virus to transcribe its own RNA into a host's DNA. The retroviral DNA can then integrate into the chromosomal DNA of the host's cells. To put it another way, a reverse transcriptase permits the virus to insert copies of its own genetic material into the cells it has infected. In this way the virus avoids detection by the hosts own antibody protection and, in some cases such as FIV, even attack antibodies themselves. Although many of the diseases caused by FeLV and FIV are similar, the specific ways in which diseases are caused will differ.

How common is the infection?
FeLV infected cats are a worldwide phenomena. In the United States, it's estimated that 2-3% of all cats are infected with FeLV. And, rates rise to13% or more in cats that are ill, in young kittens, or other reasons for high risks of infection usually related to damaged or weakened immune systems. In general, the prevalence of infection will vary relative to your cat's age, health, environment, and lifestyle.

How is FeLV spread?
Commonly, cats infected with FeLV serve as a source of infection for uninfected cats and kittens. The virus is shed in very high quantities in saliva and nasal secretions; in urine, feces, and in milk from infected queens to her kittens. Since FeLV is species specific, cats can only transfer the disease to other cats. The transfer of the virus can occur from a bite wound, during mutual grooming, and, although rarely, through the shared use of litter boxes and feeding dishes. Transmission is also possible from an infected mother cat to her kittens, either before they are born or while they are nursing. FeLV doesn't survive long outside a cat's body, less than a few hours under normal conditions. This characteristic is good to remember if you find yourself caring for an infected cat or kitten.

Where can your cat get an FeLV infection?
Cats are at greatest risk of infection when:

Your cat is exposed to another infected cat. Either through prolonged close contact or through bite wounds. Including cats living with infected cats that have an unknown infection status.

Cats are allowed outdoors unsupervised, where contact with infected cats is possible.

And, sadly, kittens born to infected mothers.

Kittens are much more susceptible to infection than adult cats because of their immature immune systems. But, as cats age and mature, especially when provided with a healthy lifestyle and environment, they develop increasing resistance to FeLV infection accordingly. For example, the degree of exposure to FeLV virus sufficient to infect 100% of young kittens will infect only 30% or fewer of those same kittens when they reach adulthood. Without question though, healthy adult cats will become infected if sufficiently exposed.

What is the effect of FeLV on a cat?
The feline leukemia virus adversely affects a cat in different ways:

It's the most common cause of cancer in cats.
FeLV can cause various blood disorders.

Most significantly, it can lead to a state of immune deficiency that hinders a cat's ability to protect herself against normally benign infections.

The same bacteria, viruses, protozoa, and fungi that are found in a cat's everyday environment can cause severe illness in cats with a weakened immune system. These infections are called secondary infections and they're responsible for most of the diseases associated with FeLV.

Are their any signs of FeLV infection?
During the early stages of infection, there usually no signs of the disease at all. But, weeks, months, or even years later a cat's health will progressively deteriorate and be characterized by recurrent illnesses separated with periods of relatively good health. Signs include:

Loss of appetite.

Slow but steady and progressive weight loss, finally followed with severe wasting late in the disease prognosis.

Persistent fever.

Pale gums and other mucus membranes. Also, inflammation of the gums (gingivitis) and mouth (Stomatitis)

Poor coat condition.
Infections of the skin, urinary bladder, and upper respiratory tract.

Persistent diarrhea.

A variety of eye conditions.

Enlarged lymph nodes.

Seizures, behavior changes, and other neurological disorders.

Un-spayed female cats may experience the abortion of her kittens or other reproductive failures.

There are two stages of FeLV infection.
When FeLV is present in the blood, it's a condition called viremia. Subsequently, there are two different stages of infection:

Primary Viremia - This is the first stage of FeLV virus infection. Some cats are able to develop an effective immune response to this early stage of infection. They are able to eliminate the virus from the bloodstream and halt progression of the virus to the second, fatal infectious stage.

Secondary Viremia - The later stage of infection is characterized by persistent infection of the bone marrow and other tissue. When FeLV infection progresses to this stage the outcome is final and the cat will be infected for the rest of her life. Her immune system will deteriorate and she will experience persistent illnesses and other symptoms of the diseases presence.

Diagnosis of FeLV is accomplished with two types of blood tests. Both are designed to detect a protein component of the virus while it circulates in the bloodstream.

ELISA - This and similar tests can be performed in your veterinarian's office. This test can detect both Primary and Secondary stages of Viremia.
IFA - This type of test will be sent out to a diagnostic laboratory. IFA tests will only detect

Secondary Viremia - Obviously, the majority of IFA positive-testing cats will remain infected for the rest of their life.

Consult with your veterinarian regarding which kind of test your cat should have. In some cases, both tests should be performed and even repeated to determine your cat's true infection or hopefully, non-infection status.

What is the best prevention against FeLV infection?

The surest way to prevent infection of your cat or kitty is to eliminate their exposure to other FeLV infected cats:

If you do allow your cats to enjoy outdoor activities, provide supervision to prevent wandering and fighting.

This is a tough one. I believe the quality of life for a cat is best when she is allowed to fully exploit her natural inclinations and habits. At the same time, protecting her from the darker sides of a cat's life experience may nearly be next to impossible. Tying up or enclosing a cat eases the human conscience, but does nothing for the cat's psyche which is meant to explore, patrol, hunt and define territory. So, the question becomes does one satisfy the human needs and ego, or allow the cat to be what she was meant to be... is the argument "I'm only protecting my cat" an assertion of human selfishness that denies natural order or a statement for protection of the precious commodity of life.

Don't mix infected and uninfected cats. If you adopt a new kitty into your home that is occupied by uninfected cats, test the new kitty before bringing her home.

If you find that you have infected cats housed with infection-free cats, don't allow infected and uninfected cats to share food and water bowls or litter boxes. Ideally, infected and uninfected cats should be separated in all-encompassing and permanent manner.

Discuss FeLV vaccination of uninfected cats with your veterinarian. He will tell you that FeLV vaccination of infected cats is not beneficial. FeLV vaccines are widely available, but since not all vaccinated cats can be fully protected, preventing exposure remains most important even for vaccinated pets. One good thing, FeLV vaccines will not cause cats to receive false positive results on ELISA, IFA, or any other available FeLV tests.
Managing FeLV-infected cats

FeLV-infected cats should be confined indoors to reduce their exposure to other infectious agents, especially those carried by animals. This will also prevent the spread of FeLV infection to other cats.

Other things to do:
It is very important to spay or neuter FeLV-infected cats. This will prevent kittens being born with the Feline Leukemia Virus and put a major block to its spreading through the cat kingdom.

Keep her as healthy as possible by feeding nutritionally complete and balanced diets. This will go a long way to helping her maintain the strongest possible immune system.

Because the risk of food-borne bacterial and parasitic infections is much higher in cats with suppressed immune systems, avoid uncooked foods such as raw meat, eggs and unpasteurized dairy products.

Visit your cat's veterinarian at least once every six months. Pay special attention to the health of gums, eyes, skin, and lymph nodes. Since weight loss is the first sign of deterioration, weight you cat regularly. Notify your veterinarian of any changes in your cat's health immediately. To date, there is no cure for FeLV.

It's not possible to predict the life expectancy of FeLV infected cats. Under the most ideal circumstances, your cat can remain in apparent good health for many months. Most infected kitties succumb within 2-3 years after becoming infected.

If your household has been home to a cat infected with the Feline Leukemia Virus, you will need to take certain steps to cleanse her environment, especially after she passes. As stated earlier, the FeLV virus will not survive outside a cat for more than a few hours. Because FeLV-infected cats are frequently infected with other non-FeLV and sometimes hardier infectious agents, they will pose a threat to any newcomer. Thoroughly clean and disinfect, or better yet, replace food & water dishes, bedding, litter pans and buy new toys. Use a dilute solution of household bleach (4 ounces of bleach per gallon of water) to make an excellent disinfectant. Don't forget to vacuum carpets and mop floors. Importantly, any new cats or kittens should be properly vaccinated before bringing them home.

Oh... and don't forget to neuter all your cats, too.

See you next time
Robert J Gallegos