Strengthening Foal Immune Systems, Preventing Pneumonia
Dr. Noah Cohen, professor and associate department head for research and graduate studies in the Department of Large Animal Clinical Sciences at the Texas A&M College of Veterinary Medicine & Biomedical Sciences (CVM), is leading the search for an effective strategy to prevent diseases caused by Rhodococcus equi (R. equi), a bacterium that commonly causes diseases like pneumonia in foals and in humans and animals with suppressed immune systems.
R. equi may not always cause disease in an infected animal, but when it does, pneumonia is most often the disease that develops. R. equi frequently infects the lungs of foals, causing severe symptoms, such as fever and coughing, which can potentially lead to death. In addition to disease in the lungs, R. equi can affect bones, kidneys, the intestinal tract, and other parts of the body.
To combat this potentially deadly pathogen, clinician-scientists like Cohen are working to develop strategies other than antibiotics that stimulate the patient’s immune system to help protect them from infection.
Coming to the CVM
In 1988, Cohen came to the CVM as an assistant professor in veterinary public health. However, his interest in applying epidemiology to large animal medicine soon led him to a residency in large animal internal medicine at the CVM. “I was honored and excited about my residency,” he said. “There were outstanding equine internists at Texas A&M, including Drs. Kent Carter, Joe Joyce, Tom Kasari, Bill McMullen, Dub Ruoff, and Allen Roussel. I knew that the excellent clinical training would enable me to identify critical questions for research. The opportunities and clinical questions seemed endless.”
Before he started his residency, Cohen had the opportunity to meet Dr. Ronald J. Martens, the department head of what is now the Department of Large Animal Clinical Sciences. Several years before Cohen came to the CVM, Martens founded the Texas A&M Equine Infectious Disease Laboratory (EIDL) to combat infectious diseases such as those caused by R. equi. Martens’ work in infectious diseases as a clinician-scientist inspired Cohen to complete his residency and join the faculty of the CVM.
“Dr. Martens had the vision to recognize that a clinician-scientist with an interest in epidemiology would be of benefit to the department,” Cohen explained. “He encouraged me to complete my residency training in internal medicine, and then he recruited me to become a member of the large animal medicine faculty.”
After he completed his residency, Cohen began researching R.equi in the EIDL under the direction of Martens. The main goal of Martens’ research was to find an effective preventative measure against infections caused by R. equi in foals because none previously existed.
Treating pneumonia caused by R. equi can be difficult because treatment is lengthy, expensive, must be administered multiple times daily, can cause serious side-effects, and isn’t always effective. This is why Martens began working on ways to decrease foals’ susceptibility to developing disease from the bacteria.
On breeding farms, pneumonia caused by R. equi is the most common and severe form of pneumonia in foals that are between the ages of one and six months. Pneumonia is a leading cause of disease and death for foals, which has motivated researchers like Martens and Cohen to seek an effective preventative strategy against pneumonia caused by R. equi. A vaccine to directly prevent the disease would be a major breakthrough for the health of foals on breeding farms, according to Cohen.
Martens recognized the prevalence of R. equi in foals and knew the importance of preventing R. equi–related diseases, especially pneumonia. Martens’ biggest contribution to the prevention of R. equi disease was the use of hyperimmune plasma, which is harvested from the blood of horses that were vaccinated to produce high concentrations of antibodies againstR. equi. The plasma is then transfused to foals. These transfusions partially protect foals against infection with R.equi.
“The collection and transfusion of plasma that is hyperimmune against R. equi remains the only acceptable and commercially available approach for preventing R. equi pneumonia,” Cohen said. “Unfortunately, it is not completely effective and has some other limitations, such as being expensive, labor-intensive to administer, and carrying some health risks for foals. Although the concept of preventing the disease by administering antibiotics has been demonstrated to be effective, this approach isn’t acceptable because it isn’t uniformly effective and, most importantly, can contribute to antibiotic resistance from overuse.”
Martens was also interested in identifying alternatives to traditional antibiotics to control R. equi pneumonia because of emerging resistance to drugs commonly used to treat the disease. When Martens retired, he passed on the directorship of the EIDL to Cohen.
Exploring alternative treatments of R. equi pneumonia as opposed to traditional antimicrobial drugs remains an area of interest for the EIDL. “We are working on two strategies for preventing R. equi pneumonia based on having the patient’s immune system protect them from infection rather than antibiotics,” Cohen said. “First, we are working on developing a vaccine, which is a traditional and effective approach for preventing infections. Second, in collaboration with investigators from the Texas A&M University System’s Institute for Biosciences and Technology (IBT) in Houston, we are investigating if a mist inhaled into the lungs can stimulate a foal’s immune system to protect it against R. equi infection.”
Collaboration
The CVM’s collaboration with numerous researchers worldwide is a critical component of Cohen’s goal to prevent R. equi pneumonia in foals. Cohen has collaborators in Brazil, Canada, Germany, Japan, and other countries, all of whom have contributed to the growing research in R. equi pneumonia prevention.
In addition, Cohen said his research project benefits significantly from many researchers in the United States and the CVM. “We collaborate with numerous investigators from many countries,” he explained. “We work especially close with Dr. Steeve Giguère from the University of Georgia, one of the world’s authorities on this disease. We are also fortunate to benefit from many scientists at the CVM.”
Results
To reduce the risk of antibiotic resistance, Cohen and his team are investigating new drugs and potential methods of administering preventative and therapeutic agents. After over five years of trying, Cohen and his team at the CVM have produced encouraging results with a vaccine for R. equi pneumonia in foals.
“We are exploring new approaches that we hope will be effective and not promote antibiotic resistance in R. equi,” Cohen said. “Examples include using inhaled substances that facilitate the foal’s own immune system by stimulating receptors of the immune system that eliminate R. equi, and drugs such as metal-based compounds and antibiotics that will reduce the risk of resistance.”
One Health
The strategies Cohen and his team are exploring may have positive implications for other animals, including humans. Since there are striking similarities between R. equi and Mycobacterium tuberculosis, the bacteria that causes tuberculosis (TB), their research on R. equi may give rise to potential therapies or preventives against TB in humans.
“Our vaccine research on R. equi might be an appropriate strategy for preventing TB, which would be of global importance for human health,” Cohen explained. “Additionally, the strategy developed by Dr. Gerald Pier and his colleagues at the Harvard Medical School, with whom we collaborate, is innovative and could lead to a ‘broad-spectrum’ vaccine that is effective against many infectious agents.”
The One Health Initiative, which stresses the connection between animal health, human health, and the environment, is an integral part of Cohen’s research. “Although our hearts and minds are committed to improving equine health, we are very much engaged in the One Health Initiative with our activities,” he said. “Developing new types of antibiotics and vaccines that can reduce the need for antibiotics is important for equine and human health because bacterial diseases remain important causes of disease for all species, and the emergence of antimicrobial resistance is a global health crisis in veterinary and human medicine.”
Research Support
As Cohen continues his research on R. equi, he links his accomplishments and new findings to the support that Martens provided him when he began his journey at the CVM. Martens was more than an administrator or a clinician-scientist for Cohen to look up to; he was a mentor.
“I learned so much from him, and we worked synergistically,” Cohen said. “One of the most important things I learned from Dr. Martens was that research is always better when done as a team. Martens was a role model for leadership, and he helped create a work environment in which we could work passionately, assiduously, and enjoyably. He offered advice and humor that made it fun to come to work each day.” In addition, Cohen expressed his gratitude for the cooperation and support from everyone at the CVM because it has positively impacted the success of his research.
Before retirement from the CVM, Cohen hopes to develop a vaccine to control R. equi pneumonia because “it is of global importance.” He would like to help shift the emphasis of treating infectious bacterial disease with antibiotics to methods that help the patient’s immune response protect them against infection. This is of utmost importance because bacteria are rapidly developing resistance to antibiotic treatment.
Cohen also recognizes the significance of students, believing they are the leaders of tomorrow. He aspires to make a positive impact on students by encouraging their research efforts. “During my time at the CVM, I would like to have trained scientists, including veterinary clinician-scientists, whose future contributions will far surpass mine,” he said.
More About Dr. Noah Cohen
Cohen’s interest in veterinary epidemiology and large animal internal medicine led him to the CVM, where he began researching R. equi in the late 1980s; however, his passion for epidemiology developed during his childhood.
“I was born in Pennsylvania, but I spent my middle school and high school years in Switzerland and Israel because of my father’s work,” Cohen said. “My father was a veterinarian who was interested in zoonotic diseases, and this strongly influenced my career. He worked for many years at the University of Pennsylvania’s School of Veterinary Medicine. I spent a lot of time at the Bolton Center, the university’s large animal hospital, where I fell in love with the idea of being an equine veterinarian.”
Cohen attended the University of Pennsylvania where he earned his undergraduate degree in oriental studies with a minor in biology and his VMD (Veterinariae Medicinae Doctoris). After he earned his VMD, Cohen spent over two years in private equine practice in and around Toronto and Ontario, Canada. He then earned his MPH and Ph.D. in epidemiology from the Johns Hopkins University School of Hygiene and Public Health, now known as the Bloomberg School of Public Health.
“At Penn, I benefitted greatly from a liberal arts education and the challenge to think and work independently,” Cohen explained. “In veterinary school, I had teachers whose expertise and dedication to excellence inspired my career. At Johns Hopkins, I was exposed to clinical and research excellence, and the principle that optimal clinical medicine and biomedical research are inextricably linked.”
Cohen continued, “I was trained by superb clinicians and fellow residents in the art and science of clinical medicine at Texas A&M. I also learned about the extraordinary commitment that clinical faculty have for teaching veterinary students. My mentors at Texas A&M instilled in me the ‘students first’ attitude that is a cornerstone of Aggie education. I cherish each of these three institutions for enabling me to do what I love: to teach, to learn, and to help others reach their goals.”
