Fernanda Cesar, DVM, MS, PhD candidate at the University of Kentucky (UK) Gluck Equine Research Center, discussed using hyperimmune plasma (HIP) to prevent Rhodococcus equi in foals at the 6th Annual Kentucky Breeders’ Short Course, held Jan. 24 in Lexington. Other authors on this paper included Macarena Sanz, DVM, MS, Dipl. ACVIM, and David Horohov, PhD, also of the Gluck Center.

R. equi, a bacterium that is found worldwide, is the leading cause of pneumonia in foals 1 to 6 months old and has a mortality rate ranging from 1% to 20%. Current antibiotic treatments for infected foals are administered orally and are prolonged and expensive.

There is no approved vaccine against R. equi. Farms with a history of R. equi infections often use ultrasound screening and aggressive antimicrobial treatments to detect and treat infected foals. However, this approach has contributed to the appearance of antimicrobial resistance in R. equi.

Another preventive approach is to administer HIP to foals at birth with a second dose at 4 to 8 weeks. The HIP contains antibodies against R. equi, which are thought to provide protection to the foal. While the exact mechanism of this protection is unknown, Cesar focused on those antibodies directed against virulence-associated protein A (VapA), an important pathogenic factor of R. equi