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The Vet Specialist

A visit with Leah Cohn, Professor of Small Animal Internal Medicine

By Spencer Melgren
Published: - Topics: veterinary medicine animals immunology microbiology

Many animal owners look to their community veterinarians for routine checkups, immunizations, and treatment of minor illnesses and injuries. Community practice veterinarians are general practitioners, like family doctors. However, like family doctors, community practice veterinarians may see patients that could benefit from the care of a specialist. Dr. Leah Cohn, Professor of Small Animal Internal Medicine and Director of Graduate Studies for the Department of Veterinary Medicine and Surgery, wants people to know that veterinary specialists exist, and at the University of Missouri Veterinary Medical Teaching Hospital, those specialists are on call to help.

Dr. Cohn is a specialist with a focus on “infectious, immune-mediated, and respiratory diseases.” Dr. Cohn tells SyndicateMizzou that she “can’t remember ever wanting to be anything but a veterinarian,” and that she has been working with animals since her first position at a veterinarian’s office at the age of 12. After earning a BA in Animal Science, she went on to obtain a Doctor of Veterinary Medicine degree in her home state of Tennessee, and then elected to pursue specialization training involving a one year internship and a three year residency in internal medicine. After specialization training, Dr. Cohn’s interest in research and teaching led her to pursue a PhD in veterinary microbiology and immunology, as well as a postdoctoral fellowship in immunology. Dr. Cohn’s early interest in veterinary medicine has lead to a distinguished career at the University of Missouri over the past 18 years.

Specialists like Dr. Cohn are extremely important in Missouri, where the large tick population and prevalence of tick-transmitted diseases are significant dangers to animal health. One particularly deadly tick-borne disease, Cytauxzoonosis, is currently the main focus of Dr. Cohn’s research. Known colloquially as “bobcat fever,” Cytauxzoonosis was discovered at the University of Missouri in the mid 1970s and described by Dr. Joseph Wagner. The disease is caused by a complicated protozoal organism named Cytauxzoon felis (C. felis). The “reservoir species” for C. felis is the bobcat, which roams nearly the entire continental US. Bobcats infected with C. felis—for reasons not yet completely understood—are able to live through the infection and become persistent carriers of Cytauxzoon. Ticks that feed on bobcats can contract C. felis and spread the infection to any other felines, including domestic cats.

Dr. Cohn’s interest in Cytauxzoonosis arose from seeing infected cats at the veterinary hospital. Once a cat is inoculated with C. felis, the course of infection is quick, painful, and difficult to combat. In the hospital Dr. Cohn saw healthy cats in the prime of life deteriorate and die within a matter of days, experiencing symptoms so horrible that Dr. Cohn likens the condition to “Ebola virus for cats.” Worse, Dr. Cohn was unable to help, as the recommended treatment for Cytauxzoonosis was an anti-protozoal drug that only saved a quarter of infected cats.

Dr. Cohn says these experiences drove her to seek a better treatment for Cytauxzoonosis. Her investigation into new treatment options led her to consider a combination of drugs that had been found useful in combating other protozoal infections. Dr. Cohn combined an antimalarial drug called atovaquone with an antibiotic called azithromycin, and tested the combination on a small set of naturally infected cats. The sample yielded more survivors than usual, which led her to develop a prospective clinical trial in collaboration with veterinary offices across the country. When the data from the trial was analyzed, “it was overwhelmingly clear that the atovaquone-azithromycin combination was far superior to the old drug,” Dr. Cohn tells us. Within the study, cats treated with this combination drug had a survival rate of 60%, a remarkable improvement over the previous one-in-four odds. “On the other hand,” Dr. Cohn is quick to point out, “the bad news is, that if 60% of cats survived with the best treatment we have available, that means 40% of the cats still died…so we certainly still have more work to do in figuring out how best to deal with this horrible, devastating infection.” This remaining work includes addressing “many unanswered questions about how the cat’s body responds, what goes on as far as the immune response, and are there ways we can improve that [response] so they don’t become as sick to begin with or are able to fight off the infection,” Dr. Cohn tells us. Moving forward, she is interested in finding a potential vaccine, better methods of treatment, and additional therapies that might improve the survival rate beyond 60%. Cytauxzoonosis—once considered a regional issue—is now seen in the majority of US states. This expansion makes understanding C. felis all the more important, and lends even greater significance to the future of Dr. Cohn’s groundbreaking research.

In addition to infectious diseases, Dr. Cohn also studies immune-mediated and respiratory diseases. In the Comparative Internal Medicine Lab, Dr. Cohn collaborates with Dr. Carol Reinero to research better ways of treating asthma in both cats and humans. “One of the few animal species that gets a disease that is essentially just like human asthma, is the cat,” Dr. Cohn says. The similarities between asthma in humans and asthma in cats present an interesting opportunity for researchers. “The fact that cats act a lot like people is handy, because we can use some of the ideas from people and see if they’ll work in cats, and we can develop ideas in cats that might be helpful to people,” Dr. Cohn says. “So, in this sense, cats can serve as a model of human asthma, but it doesn’t only benefit people, it benefits the cats.”

Another valuable service Dr. Cohn provides is directing the blood bank program at the University Veterinary Medical Teaching Hospital. The blood bank program has both cat and dog donors that live at the hospital and are cared for by hospital staff and volunteers. Dr. Cohn says that, while there are commercial blood banks, having live-in donors “allows us flexibility in preparing products on an as-needed basis, banking products, [and] having specialized blood products to provide the absolute best care for our hospitalized patients.”

In addition to her other duties, Dr. Cohn carries an extensive teaching load. She delivers lectures in both graduate and undergraduate courses on subjects including internal medicine, respiratory medicine, infectious diseases, immune-mediated disease, and other topic-specific issues. Dr. Cohn also teaches graduate courses in endocrinology and immunology. At the University Veterinary Medical Teaching Hospital, Dr. Cohn does clinical rounds in internal medicine helping vet students get hands-on experience while affording them the benefit of her experience and research. Dr. Cohn believes that her teaching helps her research by exposure to new questions and different points of view. “Students have a terrific way of seeing new and different angles on a problem and bringing those to your attention,” Dr. Cohn tells us, “so students help with research just by bringing their unique point of view to a variety of different topics.” Dr. Cohn’s research also contributes to her teaching, she says, by enabling her to provide students with the best and most current information; “I now can teach the veterinary students more about how to help prevent…or treat Cytauxzoon once it’s recognized, thanks to the research I’ve done.”