COLUMBIA — MU's Department of Veterinary Medicine and Surgery is leading the defense against a fatal feline blood parasite that is spreading via ticks and bobcats mainly in the southeastern U.S.
Leah Cohn, a professor and associate department chair of veterinary medicine and surgery, is the head clinical researcher studying the protozoan Cytauxzoan felis, which is causing the fatal disease Cytauxzoonosis in domestic cats.
While the disease is not common in central and northern Missouri, it is believed to be spreading.
It spreads from bobcats to ticks, and then ticks to domestic cats.
Disease prevalence in populations is unknown, but studies are under way to determine that.
Symptoms can include a pale to white gum line, lethargy, jaundice coloring and possible fever.
Jennifer Reisdorf, a veterinarian at the Horton Animal Hospital, recommends Frontline topical flea and tick preventative to help avoid tick-spread diseases.
Leah Cohn, MU professor of veterinary medicine and surgery and head clinical researcher studying Cytauxzoonosis, suggests keeping domestic cats indoors to avoid contact with ticks.
"When it was discovered in the late 1970s here at the University of Missouri, it was believed to be a foreign African pathogen which might infect livestock," Cohn said. The initial theory sparked a panic because researchers worried the disease might wipe out livestock.
But further research determined that the native bobcat was the original host, Cohn said.
The incidence in the domestic cat population is not currently known. Marie Kerl, Cohn's fellow researcher at MU, is working to determine those numbers.
Kerl said she sees the disease more often in cats in more southern parts of the state, and though it can happen here, it is uncommon in Boone County.
The disease was originally only thought to exist in Missouri, Oklahoma and especially Arkansas. Recently, the disease has been reported throughout the southeast and as far northeast as Pennsylvania.
"The disease is more common in areas of the state where bobcats are more common," Kerl said. "But that doesn't rule out the possibility of infection here."
The incubation time — the period in which the cat might have the virus but exhibits no symptoms — is roughly 12 days. Cohn said the disease can infect any feline but is fatal in domestic cats, killing them within three to five days after the onset of illness.
When the USDA — which had originally expressed interest in the research because of suspicion the disease could affect livestock — found out it only affected cats, all funding for research was dropped, and the research ended.
However, Cohn resumed the research three years ago and has received grants for clinical studies this year from the not-for-profit ALSAM Foundation and the WINN Feline Foundation. Cohn is recruiting veterinarians from across the region of infection – the southeastern United States – to participate with her clinical studies.
"With a disease that is so rapidly fatal, it's impossible for a family with a sick cat to drive it here (MU), from say, Arkansas, for research," Cohn said. "By the time the cat gets here, it's usually dead."
Jennifer Reisdorf, a veterinarian at the Horton Animal Hospital, said she hasn't seen any cases in which a definitive diagnosis of Cytauxzoonosis was possible. She said many times when an animal comes in that has similar, life-threatening symptoms, many owners choose to euthanize the pet and not pay for further inquisition as to the actual illness.
Residorf said the best way to protect outdoor pets from ticks is to treat them with Frontline, a topical flea and tick preventative. While it might help prevent infection, there is currently no cure for Cytauxzoonosis.
Cohn sends possible treatment regimens to the various doctors who choose to participate. That way, when they diagnose Cytauxzoonosis — an easy illness to diagnose because of its distinctive features in a cat's blood — they are able to try out Cohn's clinical research right there in their practice.
When the disease occurs in a bobcat, a species native to much of the United States, it's a minor illness. The majority of bobcats recover in a short time and become hosts, or carriers, of the disease.
According to the Missouri Department of Conservation, there are anywhere from 12,000 to 18,000 bobcats in Missouri. The last U.S. population count for bobcats was conducted in 1981.
The disease is not transmitted directly from bobcats to domestic cats – the two rarely come in contact. Cytauxzoonosis is transmitted by tick vectors. Common ticks bite carrier bobcats, picking up the parasite. These ticks then bite domestic cats who roam around outdoors. The domestic cats contract the illness and become severely ill in a short time.
Since disease transmission relies solely on the tick vectors, Cohn said the seasonal infection only occurs in the summer months. The late spring months are when tick populations become most active.
While Cohn is responsible for much of the clinical research, Adam Birkenheuer is doing the biological and laboratory research at North Carolina State University.
Birkenheuer and Cohn met through shared mentors and colleagues involved in the American College of Veterinary Internal Medicine, but have only been working together on Cytauxzoonosis for about three or four years. They often collaborate on new findings, but with Cytauxzoonosis they are onto something completely new.
Birkenheuer has been attempting to grow the organism in cultures. By culturing the organism, Birkenheuer and Cohn can learn much more about its structure and biology. They can even map the genome of the organism, giving them huge amounts of information.
"If we can culture the organism, we have a great opportunity to develop a vaccine." Birkenheuer said. "We're trying to do something that nobody has ever done before."
Birkenheuer said preliminary trials of the treatment have been lowering the fatality rate, but there is much left to accomplish.