Editor’s note: A letter to the editor from Fort Dodge Animal Health cited inaccuracies in this article and has been included below.

A new West Nile virus (WNV) equine recombinant canarypox vaccine received USDA registration approval on Dec. 23, 2003, and could pave the way for a new generation of equine vaccines in the United States. Merial has been developing this Recombitek equine WNV technology for three years. The company assembled a group of researchers, clinicians, and private practitioners in New Orleans, La., on Nov. 19, 2003, to review WNV and the research behind the technology. The Horse was invited to attend and report on the presentation.

Recombitek is the first recombinant canarypox DNA vaccine to be approved for use in horses in the United States, providing another WNV vaccination option. Fort Dodge Animal Health’s (FDAH) West Nile Innovator vaccine is a killed virus-type product. Another Merial recombinant canarypox DNA vaccine for influenza, Proteq Flu, was approved for use in the European Union in 2003. Several small animal canarypox vector vaccines have been used for over a decade in the United States.

Vectored recombinant DNA vaccines use an innocuous virus (in this case, canarypox) as a carrier to introduce a specifically chosen piece of a disease agent’s DNA (WNV membrane and envelope proteins in this case) into the animal’s cells to induce immunity. Canarypox virus doesn’t multiply in mammals–only canaries are affected by it, and they simply become vaccinated against canarypox if exposed. Frank Hurtig, DVM, MBA, Manager of Equine Veterinary Professional Services at Merial, said canarypox can be grown in the laboratory for decades with no mutation, which makes it very stable for use as a vector. This specific canarypox virus will readily accept insertion of foreign genes into its own large strand of DNA