E-Insight

July 2003

Colorado State Veterinarians Address West Nile Virus Vaccine/Pregnant Mares Issue

In contrast to incorrect accounts widely reported in June, veterinarians and researchers at the James L. Voss Veterinary Teaching Hospital and the College of Veterinary Medicine and Biomedical Sciences have not forwarded any adverse reaction reports of troubled births caused by pregnant mares receiving the West Nile virus vaccine in their practice to the USDA, the state veterinarian or Fort Dodge, the manufacturer of the vaccine. No members of the College's equine field service team, equine reproductive laboratory or other equine veterinarians have personally observed pregnancy loss, early or late, or deformed foals, attributed to the WNV vaccine.

CSU veterinarians are continuing to suggest to their clients that vaccinating horses according to the manufacturer's recommendations is one important step toward preventing WNV disease. They recommend that mare owners should work with their veterinarian to determine the best plan for their horses regarding vaccination against WNV as part of a complete disease prevention plan.

There have been concerns from a group of mare owners who believe the WNV vaccine may have caused deformations and/or abortions in foals. Fort Dodge, the manufacturer of the WNV vaccine, is investigating these reports of foal loss in mares vaccinated with the WNV product and the USDA Center for Veterinary Biologics also has launched an investigation. CSU veterinarians do not have adequate scientific information on these reports to make any kind of judgment and plan to await the USDA Center for Veterinary Biologics report. Once the USDA Center for Veterinary Biologics report is completed, CSU veterinarians will determine if the University's WNV vaccination practices or policies need to be revised.

Horse owners or veterinarians with concerns regarding pregnant mares receiving the WNV vaccine should contact the USDA's Animal and Plant Inspection Service (APHIS) Center for Veterinary Biologics at (800) 752-6255 or www.aphis.usda.gov/vs/cvb. Horse owners or veterinarians who believe they have witnessed adverse equine reactions to any vaccine should report the incident to the manufacturer and the USDA's Center for Biologics.