When we first got her, Arivaca had an upper respiratory infection, an eye infection, an ear infection, and giardia, plus she was malnourished.   Antibiotics and a good diet made a world of difference, and eventually everything cleared up, though the ear infection had to be treated several times.  With all those problems going on at once, though, I was really worried about her immune system.
As soon as she was old enough, we tested her for Feline Leukemia.  The first test was positive, as were subsequent tests.  She was probably born with the disease or acquired it when very young.  Cats can live for quite a while with Feline Leukemia, just as people can live for some time with HIV; however, I had known several cats who'd been born with FeLV or had been infected when very young, and none of them had lived past the age of two.  We tried not to think about that.  It wasn't difficult, since she was the picture of health after ditching her kittenhood illnesses.
In early September, 1999, I thought Tube seemed a little less active than usual.  It was barely noticeable and I wasn't even sure if it was my imagination, but given her medical history, I made an appointment for the upcoming Saturday just to be on the safe side.
When I came home from work Tuesday evening, I noticed her breathing was labored.  She was not in any distress or pain, but something was obviously not right.  We took her to the vet right away, where x-rays revealed a large tumor in her chest.  She had lymphoma, secondary to the Feline Leukemia.  There was no way to treat it and she would have deteriorated rapidly, so putting her to sleep was the only option.

We knew she had Feline Leukemia and we knew she would not have a normal life span, but somehow, that knowledge didn't help a bit.  Looking at pictures of her is still tough.  We always keep in mind, though, that two very positive things came out of this tragedy (see Orion's History section).