Foal Immune Responses after WNV Vaccination, AAEP 2008

A study conducted by personnel at the University of Kentucky and other institutions was aimed at determining an appropriate time for vaccinating foals for West Nile virus (WNV), reported David Horohov, PhD, at the 2008 American Association of Equine Practitioners Convention, which was held Dec. 6-10 in San Diego, Calif.

Among basic questions to be answered was whether maternal antibodies (that were passed to the foal via the mare's colostrum) would interfere with stimulation of the foal's immune response in the wake of vaccination, or whether vaccination with a WNV chimeric vaccine would stimulate a positive response. (The WNV chimeric vaccine was created by replacing the structural genes of the attenuated human yellow fever vaccine with the structural genes of WNV.) Involved in the study were 40 foals ranging in age from 3 to 5 months.



AAEP speakers Drs. David Horohov and Tracy Sturgill cover the basics of foal immunity.
Play video

The researchers reported: "Vaccinating 5-month-old foals with a single dose of West Nile virus chimeric vaccine in the presence of maternal antibodies to West Nile virus does induce a cell-mediated response (in the foal). This response is indicative of an immunologically protective Th-1 response with stimulation of cytotoxic T lymphocytes".

The study was funded by Intevet/Schering-Plough Animal Health in collaboration with the University of Kentucky's Maxwell H. Gluck Equine Research Center, the University of Florida College of Veterinary Medicine, and the Hagyard Equine Medical Institute in Lexington, Ky.

About the Author

Les Sellnow

Les Sellnow is a free-lance writer based near Riverton, Wyo. He specializes in articles on equine research, and operates a ranch where he raises horses and livestock. He has authored several fiction and non-fiction books, including Understanding Equine Lameness and Understanding The Young Horse, published by Eclipse Press and available at or by calling 800/582-5604.

Stay on top of the most recent Horse Health news with FREE weekly newsletters from Learn More