Texas A&M researchers find protein to sharpen strangles testing in horses

Researchers at the Texas A&M College of Veterinary Medicine and Biomedical Sciences have identified a protein that could improve diagnostic testing for strangles, a highly contagious bacterial disease in horses. The protein, named P92, was found to more accurately detect antibodies against Streptococcus equi subspecies equi (SEE), the bacterium responsible for the infection.

The study, published in the Journal of the American Veterinary Medical Association, compared SEE with its close relative Streptococcus equi subspecies zooepidemicus (SEZ), which commonly resides in the upper respiratory tracts of healthy horses. Existing serological tests target the SeM protein, but that protein also appears in SEZ, leading to false positives. Some SEE strains also carry mutations in SeM that can cause false negatives.

Using a microarray developed in collaboration with the University of California, Irvine, the team screened dozens of candidate proteins. P92 stood out for its ability to distinguish between horses with strangles and those exposed only to SEZ. A new serological test based on P92 proved more accurate than the standard SeM-based test, and because it relies on a single protein, it may be technically easier and less expensive to produce than a two-protein test used in the United Kingdom.

Dr. Noah Cohen, a university distinguished professor at the VMBS, called the result a happy surprise, noting that most research efforts in this area fail. The technology has been licensed by Southwest Veterinary Diagnostics, which is also developing a rapid lateral-flow test to detect P92 itself, similar to an at-home COVID-19 test. That stall-side test could give veterinarians and horse owners a faster way to diagnose strangles without sending samples to a lab.

Cohen is also collaborating with Baylor College of Medicine to explore whether mRNA encoding P92 could become part of a new strangles vaccine. More research is needed to confirm P92's accuracy across broader horse populations, but the discovery opens the door to improved diagnostic tools.