New & Now

Feline Fever: A novel drug combination may lessen C felis’ grim toll.

HOUSE CATS enjoying an outdoor excursion often encounter ticks, those tiny arachnids whose bloodsucking bites are distressingly common in the warm-weather months. For most, tick attacks are little more than an annoyance. An unfortunate few, however, suffer consequences that are very severe indeed.

Cytauxzoon felis is a protozoan parasite that thrives in the bloodstream of big cats such as the North American Bobcat, a feline species that seldom has problems tolerating it. Ticks feeding on bobcats serve as a vector for C. felis, sharing the protozoa with whatever mammal provides them with their next blood meal. When that mammal happens to be a domesticated cat, devastating illness can ensue.

Veterinarian Leah Cohn, an MU professor specializing in small animal internal medicine, likens a cat with a C. felis infection to a human with Ebola. Around 10 days after exposure to the disease — cytauxzoonosis, or “bobcat fever” — cats become lethargic and refuse to eat. As the infection progresses, she says, they become anemic, have trouble breathing, and their organs fail.

In the recent past, more than 75 percent of infected cats died within days of contracting the illness. Now the odds are better, thanks largely to a drug protocol developed by Cohn and Adam Birkenheuer, an associate professor at North Carolina State University.

Cohn and Birkenheuer’s treatment involves combining two commercially available drugs. One, azithromycin, is an antibiotic. The other, atovaquone, is an anti-protozoal treatment that has been used successfully against malaria. In a study completed earlier this year, the researchers determined that survival rates for cats treated with the two drugs improved significantly.

“Previous treatment methods have only been able to save less than 25 percent of infected cats, but our method, which is now being used by veterinarians across the country, has been shown to save about 60 percent of infected cats,” Cohn says. “While that number isn’t as high as we’d like due to the deadly nature of the disease, our method is the first truly effective way to combat the disease.”

The obvious next step for researchers, she adds, is to develop a vaccine. In the meantime, Cohn urges cat owners to do everything they can to reduce pets’ tick exposures.

In states like Missouri, where cytauxzoonosis is endemic, cat lovers need to be particularly vigilant. Keep cats indoors as much as possible, Cohn advises, while keeping dogs in the household tick-free (dogs don’t get the disease, but may bring infected ticks into contact with their feline friends). Cats that become lethargic and lose interest in food need help right away.

“The disease acts very quickly and can kill a cat less than a week after it begins to show signs of being sick, so it is important to get treatment from a veterinarian as soon as the cat appears ill,” she says.

Cohn’s findings on cytauxzoonosis have been published in the Journal of Veterinary Internal Medicine, the Journal of Veterinary Pharmacology and Therapeutics, and the Journal of Veterinary Parasitology.

Cat scratching his ear. Photo by


Reader Comments

Silvia Burns wrote on June 23, 2014

I had 3 cats dying since memorial day the first on on memorial day than 9 days later the second one and on the 21 this week end the 3rd on 3 ticks with the paresite ? We didn't know that this is existing we never had any problems or cats dying that's a painful death and I am so scared that it's not over all the cat's. are in the house and don't get to go outside since Thursday and I watch for symptoms

Ann wrote on August 6, 2014

Thanks so much for your post on cytaux-zoonosis. I have had many cats die of this dreaded disease and do fear it. Nothing much can be done to prevent it, so, of course, I am extremely eager for a vaccine to be developed. My thanks to Leah Cohn and Adam Birkenheuer for all their research.

Andrew Provost wrote on September 25, 2014

I had a one year old kitten die of Cytauxzoonosis. I thank Leah Cohn and Adam Birkenheuer greatly for what they try to accomplish. I will do whatI can at my school to raise funds and donate them to the University of Missouri veterinary college. I used this and many other web sites to write my science report on the disease.

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