THE ODDS WERE HIGHLY AGAINST DUMPLIN DYING OF
FELV ASSOCIATED ILLNESS, AND YET,
HE DIED NONETHELESS FROM IT.

Even a tiny chance of your cat getting infected with FeLV is deadly.

Our cat Dumplin, when we lived in Austin, was tested FeLV negative. He was not able to contact outside cats while in Austin, since he was always a house cat after we took him in.

About two years before Dumplin developed a swelling in his throat later, diagnosed as lymphosarcoma, a female stray snuck into the house as my wife walked into the door.
Cats can be fiercely territorial, and Dumplin immediately attacked this interloper to
drive her out. As soon as my wife and I could break it up and throw blankets over
the cats and separate them, we got the stray out. We didn't know it, but Dumplin
was then infected.

Now, here's where it gets a bit odd. Dumplin had received the first of the vaccinations given to give some protection from FeLV. The Vet advised us not to get the second part of the injection, that the first part was enough. So, Dumplin had received the first injection against FeLV. Secondly, studies have suggested strongly that the vast majority of wild / feral cats are negative for FeLV, i.e., not infected. In fact, the estimate is that
only FOUR PERCENT of feral cats are infected with FeLV.

http://from-feral2domestic.com/FIVtest.html

"Contrary to common assumptions about feral cats, there is no evidence to suggest that the majority of feral cats are in poor health or are any more likely to be infected with FeLV or FIV than domesticated cats. Certainly, kitten mortality is high—at least half of all feral kittens born never reach adulthood. If they do, their immune systems are able to fight off most viral and bacterial infections. Studies show that between 1 and 5 percent of the domestic (socialized) cat population in the U.S. is infected with FeLV or FIV. "

That means that only FOUR out of ONE HUNDRED feral cats you might encounter, would be FeLV positive.

Now, you note that it says that if feral kittens reach adulthood, their immune systems are able to fight off most viral and bacterial infections. "Studies show that between 1 and 5 percent of the domestic (socialized) cat population in the U.S. is infected with FeLV or FIV".

Most other studies claim that most adult cats are immune to FeLV, and that it is mainly the kittens that are at the most risk of contracting the diseases associated with FeLV.

And, quoting from the same above source, consider this :
" Feline Leukemia Virus\FeLV

Feline leukemia virus is a retrovirus belonging to the oncornavirus subfamily, which means it is a cancer-causing virus. In addition to causing feline leukemia, FeLV causes severe anemia and suppresses the cat's immune system, leaving the animal vulnerable to a variety of opportunistic diseases. Infected cats shed FeLV primarily in their saliva, although the virus is also present in the blood, tears, feces, and urine. Most cats acquire FeLV from their infected mothers. Other modes of FeLV transmission include mutual grooming, sharing food dishes, and fighting. Fortunately, FeLV cannot survive very long outside a cat's body. The virus loses its infectivity within minutes or hours if left at room temperature, and it can easily be destroyed with most disinfectants and detergents.

How FeLV exposure affects a cat

One of three things can happen when a cat is exposed to FeLV. The cat may experience a transient viral infection and then fight off the virus, developing future immunity. There is evidence that up to 70 to 80 percent of adults exposed to FeLV survive the initial stage of infection and acquire immunity. (Emphasis added) Kittens under 16 weeks are much less likely to overcome a viral attack. If the cat does not overcome the initial infection, the virus eventually moves to the bone marrow, and the cat becomes persistently infected, or viremic. Even though a persistently viremic cat may be asymptomatic for several years, he or she will usually develop FeLV-related diseases at some point. Persistently infected cats shed the virus throughout their lives, becoming a source of infection for other cats with which they come in contact.

A third possibility is that the cat is able to produce an effective immune response to the infection yet continue to harbor the virus somewhere in the body. A latently infected cat does not appear to be susceptible to FeLV-related diseases and does not shed the virus the way a persistently infected cat does, so there is no risk of infecting other cats. The latent phase of a FeLV infection seems to be temporary for most cats, which become free of the virus within a few years after the infection occurs. However, latently infected cats do occasionally become persistently viremic. "

So, if you combine the extremely small chance that ANY feral cat that gets into a house is FeLV positive, with the fact that 70-80 percent of adult males survive the intial attack of FeLV and become immune, it becomes more and more bizarre, that our cat Dumplin, who had received the vaccination against the disease when he was younger, died from the disease around 2.5 years after infection.

Now, combine this with the fact that apparently, the virus had moved to Dumplin's
bone marrow, with the fact that he was, per the doctors, NOT SHEDDING the virus, it becomes even more and more odd to me.

Now, remember that there was only ONE incident in which possibly, an FeLV
infected cat contacted our cat (we never saw the female stray again, so we can never be 100 percent she was FeLV positive, though that is the assumption everyone has made), consider the following statement :
(The first way the site says a cat can become infected is as a kitten, but
read the number two way)

"(2) Cat-to-cat infection occurs only where there is prolonged, intimate contact between cats. The virus is shed in the saliva of infected cats and dies very rapidly once outside the body, so it is only likely to be transmitted as a result of close contact with an infected cat. This means mutual grooming, sharing of feeding bowls or actual biting are necessary for the infection to be passed on. Note the difference from transmission of FIV, where an actual bite is necessary for the infection to be passed to another cat - sharing of feeding bowls and mutual grooming is not considered to be a channel of infection.
FeLV is also found in tears, nasal secretions and urine from infected cats, but this is much less likely to be a source of infection to another cat than saliva. Blood is another source of infection and blood donors should always be screened for both FeLV and FIV."

There was no "prolonged" contact, just a very brief cat fight !

If one were a betting person, and you could bet that, a random feral cat,
who has a brief cat fight, with an adult cat, who has received the first
part of the vaccination, and has not been exposed to other FeLV positive cats, knowing only 4 percent of the feral population are probably FeLV
positive, and that 70-80 percent of healthy adult cats will develop immunity
after the initial contact with the virus, would you bet such a cat would die
from the disease in two and a half years? No, and neither would I, but,
that is apparently what happened to our sweet Dumplin, and I for one
am trying with all my might to make sense of it, and see what benefit
I can get from studying this, that might protect other cats.

To see how weird this is, consider this citation from this site
 http://www.catactiontrust.org.uk
"...Positive cats should be re-homed to households without other cats (certainly without kittens). However, this should not be adhered to so strictly that the welfare of the individual cat is forgotten, since the risk of transmission between adult cats is actually quite small. 85% develop their own immunity to Feline Leukaemia, but if they have not been tested for this,or they are tested and found to have no immunity, they may be vaccinated against it, and that apart, they are simply not easily infected with the virus."

And then, there's this :
 http://findarticles.com/p/articles/mi_hb5101/is_/ai_n29264558
" FeLV and FIV May Be Decreasing

Sorry for the alphabet soup, but this time the news about feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) is better. Sort of.

Reporting in the Journal of the American Veterinary Medical Association (Vol. 228, No. 3), veterinary researchers at the University of Florida in Gainesville and at Texas A&M in College Station say that their most recent study found these rates in cats: 2.3 percent were seropositive for the FeLV antigen, 2.5 percent were seropositive for the FIV antibody, and 0.3 percent of cats seemed to be infected with both viruses.

Compare that to a large national study 10 years ago that found 13 percent of sick or at-risk cats to be infected with FeLV and seven percent with FIV. Yet a 1998 study found much lower prevalence in otherwise healthy cats: 1.3 percent were positive for FeLV and 0.9 percent for FIV. And a study of 1,876 ownerless feral cats reported prevalences of four percent for each virus.

After slicing and dicing the data a hundred different ways, the researchers had this advice: Because cats in all categories are still at risk, owners and veterinarians should follow current guidelines "to test all cats at the time of acquisition and again during illness ... whenever possible."

With all this, is it any wonder that I am very, very confused about how
a fairly healthy indoor adult cat like Dumplin, who had received the first part of the FeLV vaccination, could be ending up terminally infected with FeLV?

The battle for understanding goes on.