Veterinarians have been using an antibody product to treat West Nile virus (WNV) clinical signs, but its use for this purpose is currently off-label (not approved by the USDA). Currently, the hyperimmune plasma product HiGamm-Equi, by Lake Immunogenics, is being examined by the USDA for conditional approval.

HiGamm-Equi is typically used for failure of passive transfer in foals--the horses from which the plasma is taken are heavily vaccinated against a multitude of diseases so that antibodies get passed on to the plasma recipient. In recent years, donor horses have been vaccinated against WNV, and tests have been performed to determine that grown horses given the plasma develop a WNV antibody titer of 1:20, which James L. Bowman, DVM, president of Lake Immunogenics, said is effective. He also reported that the firm’s study in hamsters indicates that the product is effective in eliminating the virus in the bloodstream when given before or after WNV challenge.

The plasma is frozen after collection and sent to veterinarians, who administer it intravenously. One treatment for an average size horse costs about $200, although prices vary.

This is the second WNV season in which Maureen Long, DVM, PhD, Dipl. ACVIM, assistant professor of large animal veterinary medicine at the University of Florida, has used HiGamm-Equi, and she has been pleased with the results. "It will be an important product to use in foals that have passive transfer failure in West Nile virus-active areas," said Long. "Or if you buy a horse and bring it to an area where there’s an outbreak occurring, you can give plasma and get him protected."

As with any treatment, HiGamm-Equi should be given early, and it needs to be administered before the horse becomes recumbent.


About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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