West Nile Virus Vaccination

The following responses to questions are from Rob Keene, DVM, a field technical consulting equine veterinarian with Fort Dodge Animal Health (FDAH), manufacturers of the West Nile virus vaccine.

 The West Nile virus (WNV) vaccine is probably one of the best-known vaccines on the market right now. How did you get it ready so quickly after WNV was found in the United States?

Many people worked tirelessly. They spent weekends and long hours to make the speedy approval of the WNV vaccine a reality. FDAH scientists also benefited from excellent basic research and diagnostic work conducted by many scientists at government laboratories, especially in USDA and CDC (Centers for Disease Control). State and federal officials responsible for review and approval of the resulting data submissions recognized the urgency of the situation and reviewed this vaccine as a high priority. Accordingly, U.S. horse owners have many people to thank for the rapid availability of this product. We are very proud of the part Fort Dodge Animal Health was able to play in this.

 Briefly, what were the steps you took to create the WNV vaccine?

The USDA regulates the development of vaccines for animals and they are intimately involved throughout the entire vaccine development procedure. So, our first step was to contact the USDA and get their input on the importance of WNV as a vaccine candidate and to get the approval process started early.

To start out, WNV master seed was established and was proved to be pure and free of any contaminants, which was subsequently confirmed by the USDA laboratories in Ames, Iowa. This pure master seed is the source of all vaccine antigen used in the Fort Dodge Animal Health West Nile virus vaccine. Then methods were developed to grow the virus in large quantities. After harvest, the virus must be inactivated with the goal of producing a safely killed (harmless) virus product that still is capable of producing protective immunity in vaccinated horses. To magnify the immune response to the best extent possible, the final formula for this vaccine was then developed, including of one of our best-known and reliable equine vaccine adjuvants--Metastim. (Adjuvants are substances that increase the immune response.) Along the way, in-process and final product test methods were developed and put in place.

Once the final vaccine formula was established and laboratory confirmation was complete, field safety and efficacy studies commenced. These studies have been published and discussed widely.

What are the problems drug manufacturers face when creating new equine vaccines?

Creating a new vaccine is very expensive. The regulatory hurdles are tremendous, and for some products they can take years to clear. There are certain disease-causing pathogens that are very difficult to work with and some (WNV, for instance) that can pose a human health risk to the scientists in the laboratory. In fact, so far it has proven to be impossible to make effective vaccines against some disease-causing pathogens. The good news is that recent advances in biotechnology are improving the quality and availability of important vaccines at a rapid pace. New vaccines directed toward solving some of these historically difficult disease problems and improved existing vaccines will be a reality in the near future.

Development of vaccines for horses can pose special challenges for companies. Horses are very expensive, and they are expensive to house and maintain for long-term research studies. Caring for 50 cats for one year is certainly much less expensive than maintaining 50 horses for that period. At the same time, the market for horse vaccines is relatively small when compared to the market for vaccines used in humans, cattle, dogs, or cats. As a result, the return on research investment for horse products must be carefully controlled by manufacturers.

 What is the most important thing for horse owners to know about equine vaccines?

Vaccines are very powerful, important keys to controlling disease spread and preventing suffering in the horses we love. But vaccines are designed to prevent disease, not to cure it. They don't work well after an animal gets sick. Vaccines must be used before the disease is contracted. Your veterinarian is the best person to help you with disease prevention and will guide you through vaccine selection, timing, and use, and to advise you on after-care of your horse.

About the Author

Rob Keene, DVM

Rob Keene, DVM, is an equine technical manager for Boehringer Ingelheim Vetmedica, Inc. (BIVI). Keene focuses on university outreach, equine infectious disease, and monitoring research projects. He has more than 10 years of equine veterinary practice experience and received his bachelor of science degree from Montana State University and a bachelor of science and doctor of veterinary medicine degrees from Colorado State University.

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