Daisy, the neighborhood cat

Let me start by saying that this is not the topic I had planned for this post. This topic was thrust upon me by Daisy, the sweet and feisty neighborhood cat to whom I refer in my bio. Since I am the only vet among Daisy’s caregivers, her medical issues become mine. Daisy is an approximately 11-year-old spayed female cat with a rather spotty vaccine history (although she is up to date, starting a year ago). She lives outdoors approximately 90% of the time (the other 10%, she’s in our next door neighbor’s house). Daisy is generally healthy and has tested negative to the nasty outdoor cat viruses (FeLV and FIV). 

In January 2009, I nearly tripped over Daisy sitting on my doorstep; she was crouched and vocalizing. On exam, her temperature was a chilly 97-ish and her heart rate was elevated. Her gums were so pale they appeared white. She stumbled as she walked and her eyes made rapid side-to-side movements called nystagmus. On blood work, the percentage of her blood that comprised red blood cells (RBCs) was an alarmingly low 6.9%. The “normal” range for a healthy cat is 35-45%. Because not many things can cause such a swift decline and severe anemia in a typically healthy cat, I was suspicious of Feline Infectious Anemia (FIA) and started treatment. At the time, Daisy had “owners,” who I knew would be responsible for only the most modest care; so I did not give her a blood transfusion but did start her on a three-week course of doxycycline (a relative of tetracycline). Daisy not only survived that first night (a miracle, in my mind) but steadily regained her health.  

Fast forward to this past Friday evening. My neighbor came to my door carrying a Daisy I barely recognized. I had not seen Daisy much in the past month and she had lost a couple of pounds. She was crouched and depressed. Her gums were white and she stumbled as she walked. I would have to wait until morning to confirm with lab work what I already knew: the FIA was back. Sure enough, her blood was only around 8% RBCs. I started her on antibiotics again and, as I write, my neighbors are taking meticulous care of her. Her former owners moved away about a year ago, so these very nice people are my new “clients,” I guess.  

So, this brings me to my topic: what is FIA and why can’t Daisy be done with it, already?  

The agent that causes FIA is an odd type of bacteria. In fact, a few years ago, it was completely re-categorized and was given a new name by the people who dictate that sort of thing. We used to call these bacteria Hemobartonella felis. But, these days, they’re known as Mycoplasma haemofelis (and, for the purists out there, the disease is technically now called “feline hemotropic mycoplasmosis” ). Any of you who have dealt with mycoplasma infections in your pets are likely quaking in your boots. Mycoplasmas are hard to diagnose because they’re nearly impossible to culture. And, when you treat them, you can’t seem to get them all. They hang around in small numbers that don’t cause any trouble – until the pet is stressed or ill. Then, presto, you have another infection.  

How do these bacteria cause such severe disease in cats? M. haemofelis is transmitted to cats by biting insects and arachnids, like fleas, ticks, and mosquitoes. There is increasing evidence that it can also be transmitted via cat bites, such as during a fight. So, you can see that a mostly-outdoor cat would be the type to acquire this disease. Once in the cat’s bloodstream, the mycoplasma attach to the surface of RBCs. When the cat mounts an immune response to these invaders, infected cells are covered with antibodies that signal the spleen to destroy the cells. Naturally, if a high percentage of RBCs are infected (and therefore destroyed), this can lead to a very severe anemia. The clinical signs, like depression or lethargy and the stumbling and nystagmus I described are due to lack of oxygen in the brain. And, although Daisy’s temperature was likely elevated early in the infection, extremely sick cats will often have a low body temperature, which suggests a very guarded prognosis.  

Diagnosis can be achieved through an advanced lab test (PCR) or response to treatment with the proper antibiotics. Sometimes the mycoplasma can be seen via microscope; but not seeing them does not rule out infection. FIA should be at the top of the list for an outdoor cat with severe anemia, and treatment started immediately.  

So, Daisy is fighting for her life again. It doesn’t really matter whether this is a recurrence of her original infection or a brand new one. I hope she has the same good response to the antibiotics. And I hope this is her last battle with FIA.