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.