One of the diseases that I most dreaded diagnosing in my feline patients when I practiced in the southeastern U.S. was cytauxzoonosis. After moving west to Wyoming, and now Colorado, I haven’t seen a single case, but I was still excited to see that a new, more effective treatment protocol is being reported in the veterinary literature.
Cytauxzoonosis is a disease of cats only. It cannot spread to people or any other non-felid animal. In fact, in cannot even be spread directly from cat to cat. The causative agent, a protozoan called Cytauxzoon felis, is transmitted via the bites of infected ticks. Bobcats are the reservoir host. Studies have shown that as many as 50 percent of bobcats may be carriers, but they typically develop few symptoms of disease. A tick can pick up the protozoa from any infected cat and pass it on via subsequent bites to other cats. Cats that spend time outdoors in the South Central and Southeastern United States are at greatest risk for cytauxzoonosis.
Cytauxzoon felis attacks red blood cells and tissues throughout the body, which incites a massive immune response. The disease presents in two different forms. Acutely infected cats are very, very sick. Clinical signs typically consist of some combination of the following:
- loss of appetite
- abnormally pale or yellow mucous membranes
- increased respiratory rate and effort
- enlarged lymph nodes
Many cats die within a week or two of developing symptoms, even with the traditional treatment protocol of supportive care (e.g., intravenous fluids, heparin, and blood transfusions) and imidocarb, an anti-protozoal drug. Those that do survive can become chronic carriers. They are seemingly healthy, but can serve as a reservoir for the disease.
The new treatment for cytauxzoonosis combines the anti-malarial drug atovaquone and the antibiotic azithromycin. Survival rates increase from around 26 percent in cats treated with imidocarb to 60 percent with the atovaquone/azithromycin combination. This still isn’t great (atovaquone is expensive, and 40 percent of cats are still dying), but it is a big improvement to the odds I faced when practicing in the Southeast.
If your cat ever develops symptoms consistent with cytauxzoonosis, see your veterinarian immediately. The doctor can determine whether Cytauxzoon felis is responsible with a blood smear and/or a laboratory blood test.
Even with the availability of improved treatment options, cytauxzoonosis is still a disease that is best prevented. If you live in a high risk area, keep your cat indoors if possible and apply an effective tick control medication that is labeled for use in cats every month.
Dr. Jennifer Coates