Zig, a handsome eight-year-old orange kitty, came in for his annual physical and vaccinations. “Zig has been a little off, lately,” the owner commented as we checked him in. “He’s not eating well lately and seems less active.”
Beginning my examination, I noted that Ziggy’s temperature was a degree above normal. Sometimes a patient’s body temperature will be slightly elevated from the car ride or nervous anticipation of a vet visit, but this was higher than expected in a healthy animal. “He’s running a low-grade fever,” I said, rolling back Zig’s lip and looking in his mouth, “and he’s very pale.”
People often look bemused if I say their pet looks pale. “How can you tell?” they ask, giggling. True, it’s hard to assess color simply by looking at a furry face. In some fair-haired cats you might notice if the nose is a nice pink hue, but the way veterinarians routinely check an animal’s color is by the gums. Animals may have grey or black pigment inside their mouths, making this task impossible, but most have unpigmented areas where we can assess the exact shade of pink. Ziggy’s gums? Almost white with a very faint pinkness and, maybe, yes, a hint of yellow. “We’ve got a problem,” I sighed. “The paleness suggests anemia and that yellow tinge is jaundice, also called icterus. Zig might have liver problems, or hemolytic anemia, with underlying causes ranging from Feline Leukemia Virus, to cancer, to bacterial infections. I think the most likely diagnosis is a thing called feline infectious anemia.” FIA, also called hemobartonellosis. First discovered in Africa in 1942, the bacterium causing FIA was originally named Hemobartonella felis, but in recent years, gene sequencing has revealed that the bug actually belongs in a different classification. It has been renamed Mycoplasma haemofelis and the illness is now called feline hematropic mycoplamosis. But I’m an old dog, so I still call it FIA.
Here’s what happens. The organism enters the circulation via a flea bite, then attaches to a red blood cell (RBC). When the immune system notices the abnormal RBC, it does the logical thing. It destroys that bad boy. That’s a good strategy — if you’ve only got a few abnormal RBCs. It becomes a problem, however, when huge numbers of RBCs are infected. After a while, the body can’t keep up making enough new, healthy RBCs and kitty becomes progressively more anemic. Hemolytic anemia means that it is the result of breakdown (lysis) of red blood cells. RBC lysis leads to release of bilirubin from inside the RBC into the circulation, which turns kitty yellow.
FIA symptoms vary widely. Some infected cats show no signs at all, while in others, FIA can be quickly fatal. Typical signs include intermittent fever, depression, weakness, poor appetite, enlarged spleen, pale gums, and jaundice. Cats who have Feline Leukemia Virus or Feline Immunodeficiency Virus are at greater risk. It is more common in young tom cats than in females, probably due to lifestyle differences like roaming and fighting that increase the risk of exposure to infected fleas. Definitive diagnosis can sometimes be made by identifying the microscopic parasites in the RBCs using special stains, but the organisms tend to occur in the blood in cycles. Hence, lack of visible parasites in the blood does not rule out the disease, even in very sick cats. A fancier option, the PCR test, detects even tiny amounts of the parasite’s DNA in the blood. It is most reliable if done before starting antibiotics.
Left untreated, up to a third of cats with FIA may die, so once we confirmed that the jaundice was not the result of liver disease, and that Ziggy was, in fact, very anemic, I prescribed doxycycline, despite the lack of a definitive diagnosis. “This is the drug of choice for FIA,” I explained “but it’s tricky to give to cats.” On rare occasions, the tablet form of doxycycline can cause serious esophageal irritation in cats, leading to irreversible strictures. The commercial liquid form is expensive and not a cat-friendly flavor. We could get it compounded into a more palatable mix, but that would take time and is also costly.
Ziggy’s owner opted to use tablets, following each dose by gently force-feeding a good quantity of water to wash it down. Three weeks of doxycycline cures most cats, although a significant percentage remain asymptomatic carriers for life. “Bring him back Monday and we’ll see if the anemia is resolving,” I advised.
Sometimes a blood transfusion is necessary to stabilize a patient while the doxycycline has time to work. Sometimes the immune system is so over-stimulated that it keeps destroying healthy RBCs even after antibiotic treatment has begun. In those cases, the corticosteroid prednisone is added to the protocol to suppress the immune system’s overzealousness.
At Ziggy’s first recheck, his RBC count was slightly improved. Testing had failed to confirm the presence of Mycoplasma haemofelis, but his apparent response to treatment supported this presumptive diagnosis. He seemed out of immediate danger, but wasn’t bouncing back as quickly as I expected so prednisone was added to the protocol, and I wrote an upbeat article about him and feline infectious anemia.
Today was his next recheck. I was confidently anticipating a nice pink nose on a happy, recovering patient. But no. He had lost more weight and was extremely pale again. Palpating his tummy, I now felt a large mass. Radiographs suggested it was likely a mass in his kidney, quite possibly cancer. “I’m afraid my initial diagnosis may have been wrong,” I explained dejectedly. “Or at least there appear to be other more serious problems as well.”
FIA is life-threatening but usually fairly treatable. Kidney cancer, not so much. We’ve sent out more tests and discussed our options. I hope Ziggy will have his nice pink nose back soon, but I’m afraid the future may not be so rosy. In the meantime, we do our best to keep him comfortable as we pursue definitive diagnosis.