Phoenix developed some of the same symptoms shortly after I adopted him, especially the listlessness. It was very difficult to have him tested for babesia, as the carrying brown ticks don't live here on Ontario. Finally I found a vet in Oakville who did the test, and it was positive. Although his titres were borderline, the critters were visible in his blood. The treatment has to be brought in from the US. I was told that babesia can be dormant for a long time, but can be activated due to stress, such as being adopted or mourning the loss of a good friend.