Vaccinating mares against the polysaccharide poly-N-acetyl glucosamine appears to effectively protect foals against R. equi pneumonia, researchers found. | Photo: Anne M. Eberhardt/The Horse

Rhodococcus equi (R. equi) is the most serious cause of pneumonia in 1- to 4-month-old foals. It is expensive to treat and sometimes fatal, yet no vaccine to protect against the pathogen exists.

So researchers from Texas A&M’s College of Veterinary Medicine and Biomedical Sciences investigated whether a newly developed vaccine administered to mares during pregnancy could protect their foals from R. equi pneumonia. Noah Cohen, VMD, MPH, PhD, Dipl. ACVIM, professor of large animal internal medicine, presented their findings at the 2017 American Association of Equine Practitioners convention, held Nov. 17-21 in San Antonio, Texas.

R. equi is a Gram-positive bacterium found in soil. Grazing animals can ingest spores and become infected, but foals generally get it after they inhale R. equi-laden particles. Treatment is prolonged and, therefore, in addition to risks of mortality, the disease has serious economic consequences