It began with a common paddock accident–crashing into a rail–and progressed into a bone infection. After several months of nursing and repeated surgeries, veterinary efforts failed to save the life of Alywow, a former Canadian Horse of the Year and million-dollar-plus Thoroughbred broodmare.

While bone infections don’t automatically end with euthanasia, they can be difficult to treat. That’s because most bone infections occur in the lower limbs, where blood flow under normal conditions is minimal, and it can be even less during active infection. As a result, the infection is harder to control.

Nicola C. Cribb, MA, VetMB, MRCVS, a resident in large animal surgery working with Ludovic Bouré, DVM, MSc, DES, Dipl. ACVS, ECVS, associate professor of large animal surgery at Ontario Veterinary College at the University of Guelph, details what happens when a bone in the lower limb becomes injured and infected:

"Lower limb infections occur when bacteria colonize bone or synovial structures, including joints, tendon sheaths, and bursa. An acute inflammation occurs following bacterial inoculation, which results in disruption of the blood supply to the affected tissue. Because joint, tendon, and bony structures in the lower limb of the normal horse are all minimally vascularized (supplied with blood vessels), this disruption of the already nominal blood supply results in protection of bacteria not only from the natural defense mechanisms of the horse, but from antibiotics that need to be carried to the site of infection in the bloodstream